Surface finish is how smooth the inside of the intake ports are. That smoothness can change how air moves and how much energy is lost as air squeezes through.
Port dividers are little “walls” inside the intake port that guide the air toward the valve. They can help the air flow more cleanly instead of separating or swirling the wrong way.
CNC porting means using a computer-controlled machine to carve out the inside passages in an engine. The idea is to make those passages match very closely every time. People compare it to hand porting because the results can feel different.
Hand porting is when someone manually reshapes the inside passages of an engine. Instead of relying on a machine to cut the shape, a person can fine-tune it. The hosts are saying that this can sometimes outperform CNC results.
An intake manifold is the set of passages that gets air from the intake to the engine’s cylinders. Its shape matters because it changes how smoothly and how consistently the engine can breathe. That’s why it’s a big deal for performance tuning.
Runner length is how long each intake tube is between the manifold and the cylinder. That length affects how the engine “breathes” at different RPMs. Changing it can shift where the engine feels strong.
The plenum chamber is like a shared air “holding area” in the intake manifold. It helps manage how air gets sent to each cylinder. Its size can change how the engine responds across the RPM range.
Thermal efficiency is a measure of how well an engine turns fuel energy into actual motion. Higher thermal efficiency means the engine wastes less energy as heat and gets more useful power from the same fuel.
Formula One is a top racing series where teams constantly test new engine ideas. The host brings it up to show that even today, engine technology is still improving.
TIG welding is a careful welding method that makes clean, controlled welds. It’s often used when you want strong, accurate metalwork—like when building parts such as manifolds.
Engines shake as they spin, and that shake can happen at certain “rhythms.” A harmonic damper is a part that helps absorb those vibrations so the crankshaft and other parts aren’t stressed as much.
Engine balance is about making the moving parts “even” so they don’t cause extra shaking. But even a well-balanced engine can still twist and vibrate because of how combustion happens cycle after cycle.
Resonant frequency is the RPM where parts start vibrating more strongly. If the engine spends time near that RPM, the shaking can build up and cause problems faster.
Valve springs are the parts that help the engine’s valves move correctly. If the engine spins at an RPM where the springs resonate, they can get overstressed and cause failures.
A harmonic dampener is a device that helps stop the engine from twisting and vibrating at certain RPMs. It needs to be matched to the engine so it actually reduces the problem instead of doing nothing.
Factory balances means the way the manufacturer designed and tuned the engine’s rotating parts. The host is saying the original setup can reduce vibration better than many aftermarket parts.
Some vibration-dampening parts use rubber to soak up shaking. The host is saying if the rubber is too hard, it won’t dampen vibrations well.
Concept
sacrificial anode
A sacrificial anode is something that’s meant to wear out first to protect other parts. The host is using it as a comparison for how a good dampener should handle vibration.
Harmonics are like a repeating “buzzing” vibration inside the engine. If something doesn’t absorb that vibration, it can make the crankshaft flex and wear things out faster.
Crank flex is the small bending or twisting movement of the crankshaft under load and vibration. Excess crank flex can increase stress on bearings and other rotating components, reducing durability and crankshaft life.
The crankshaft is the big spinning shaft inside the engine that turns piston movement into rotation. If it vibrates too much, it can cause damage to other parts like bearings.
Billet underdrive pulleys are aftermarket parts that change how fast engine accessories spin. If they reduce vibration control too much, the extra shaking can wear bearings out.
The Subaru WRX is a sporty car made by Subaru, usually with a turbo engine and all-wheel drive. People modify it with performance parts to improve how the engine and accessories work. Underdrive pulleys are one example of an upgrade that some owners use for better performance.
Fluid dampeners use a viscous fluid to absorb and dissipate vibration energy. The speaker contrasts them with other designs, noting that some fluid dampeners can last longer depending on how well the fluid’s properties match the engine’s operating conditions.
Innovative West is a company that makes vibration-damping parts for race engines. The host is saying their dampeners are designed to last because of how the silicon-based fluid behaves and how heat is managed.
An elastomer-based dampener uses a rubber-like material to reduce shaking. The discussion is about how that approach compares to fluid dampeners in real race use.
Engine reconditioning means rebuilding an engine so its worn parts work like they should again. For race engines, the rebuild has to be more precise because the engine is pushed harder and spins faster.
Machining is the precision cutting/finishing of metal parts to achieve exact dimensions. When building high-performance engines, machining is used to set critical measurements like clearances and tolerances so the engine can handle extreme heat, RPM, and load without premature wear or failure.
Tolerances are how exact the measurements have to be when making parts. Race engines need tighter tolerances so everything fits and behaves consistently when things get hot and the engine spins fast.
Thermal overload means parts get too hot for safe operation. The longer you run the engine hard, the more heat builds up, and that can cause components like valve springs to behave differently or wear faster.
A retainer is a part that holds the valve spring in position. It helps the spring push the valve correctly, and in long races heat can make small details matter more.
Concept
endurance racing engine durability vs drag-race setup
Drag racing is short and brutal, but endurance racing is about surviving for a long time. The engine has to stay healthy under heat and stress for much longer, so the build details matter more.
Concept
wide open throttle endurance vs marine operation
The speaker is saying boats can often run at full throttle for a long time, unlike most cars. That means the engine stays under heavy heat and load for longer, so the setup has to account for that.
Compression ratio is how tightly an engine squeezes the air-fuel mixture before it ignites. Squeezing more often helps power, but it can also cause the fuel to ignite too early (knock) if conditions aren’t right.
E85 is a blend of mostly ethanol and some gasoline. Because it resists knocking better than regular gasoline, it can let an engine run more compression or more aggressive settings.
Detonation is when the fuel-air mixture starts burning in an uncontrolled way, not smoothly. It can feel like a harsh knock and can damage the engine if it happens repeatedly.
Hot spots are tiny areas inside the combustion chamber that get hotter than the rest. If they get too hot, they can cause the fuel to ignite too early and lead to knocking.
The piston dome is the raised part on top of the piston. Its shape affects how the fuel burns, and certain shapes can make the burn less smooth and more prone to knocking.
This is a design idea that compares how much hot surface area the burning mixture has to touch versus how much the mixture is squeezed. A better (lower) ratio can help the burn happen more smoothly and reduce knocking.
It’s a number that tells you how well air/fuel can flow through an opening compared to a perfect case. A higher “flow efficiency” helps the engine mix and burn fuel more effectively.
After the spark, the fire doesn’t instantly fill the chamber—it spreads. Flame front propagation is how quickly that “burning front” moves across the chamber.
The spark event is when the spark plug actually ignites the air/fuel mixture. If the burn is slow, you light it earlier so the engine reaches maximum push at the right time.
Peak cylinder pressure is the highest “push” pressure inside the cylinder. Good tuning tries to make that maximum happen at the right moment so the engine gets more useful force.
The Toyota Supra is a sports car built for performance. When people talk about tuning it, they often discuss changes inside the engine, like the shape of the combustion chamber and how much compression the engine has. Those changes can affect how much power the engine makes.
Combustion chamber volume is the size of the space where the fuel burns. Changing that shape/size can change how the flame behaves and how efficiently the engine makes power.
Valve angle is how the intake/exhaust valves are tilted in the head. If the chamber shape changes, the valves may need to be angled differently, which affects how air flows in.
Term
knock-on events
It means one small change in an engine can cause other problems or changes elsewhere. Like changing airflow can lead to changes in cylinder pressure, which then affects how the engine needs to be tuned.
A “sweet spot” is the best range where the engine works most efficiently. Here, they’re saying there’s an angle range that tends to make the engine breathe and burn fuel better.
A “wedge head” is a type of cylinder head where the combustion chamber has a wedge-like shape. That shape affects how the fuel burns and how well the engine can be tuned for power.
Term
port was very low
Saying the port is “very low” is about the shape and position of the intake passage. If it’s positioned poorly, the air doesn’t flow as smoothly into the cylinder.
The “short turn” is the bend inside the intake port where air has to turn sharply. If that bend is shaped poorly, the airflow doesn’t follow smoothly, and the engine can’t fill the cylinder as well.
Term
valve up
“Valve up” means adjusting how the valve sits in relation to the intake port. The goal is to help air flow smoothly into the cylinder instead of getting stuck or disturbed.
“Boosted” means the engine uses a turbo or supercharger to push more air in. That extra pressure makes the engine stronger and faster, but it also stresses parts more, so you have to build and tune carefully.
Term
piston quality
“Piston quality” is about how strong and well-made the piston is for the heat and pressure inside the engine. Higher-power builds need pistons that can handle that stress.
Term
ring quality
“Ring quality” is about the piston rings that seal the combustion gases and control oil. If they aren’t up to the job, the engine can lose compression or start burning oil.
“Naturally aspirated” means the engine pulls air in without a turbo or supercharger. The point here is that NA engines still need the same kind of smart tuning and good parts to make power reliably.
Turbocharger sizing means picking the right turbo so it can supply the airflow you want. If it’s too big, it can feel slow to spool up; if it’s too small, it can run out of breath at higher RPM.
Inlet manifold pressure is the pressure of the air going into the engine. Higher pressure usually means the engine can get more air, which helps it make more power—especially in turbo cars.
Exhaust back pressure is how “stuck” the exhaust gases feel as they try to leave the engine. If it’s too high, the engine can’t breathe out as easily, which can limit power and response.
“1 to 1” means the pressure pushing air in is about the same as the pressure pushing back in the exhaust. He’s saying that balance can make the turbo engine act more like a naturally aspirated one.
Cam profile is how the camshaft controls when the engine’s valves open and close. Changing it can affect how the engine breathes and how it responds, especially when you add boost.
14.7 psi is normal air pressure outside at sea level. When you add boost, you’re raising the pressure above that baseline, not inventing pressure out of nowhere.
“Twin cam” means the engine uses two camshafts to open and close the valves. More than one camshaft can help the engine control airflow and timing more precisely.
Clearances are the tiny gaps inside an engine between parts that move. Setting them correctly helps the engine run smoothly and prevents parts from rubbing or wearing out too fast.
Bearing clearance is the tiny space between the crankshaft and the bearing. That space helps oil get in and keep metal parts from rubbing directly. Builders change that gap to reduce wear and prevent damage.
Oil viscosity is how thick the oil is. Thicker oil can help keep moving parts separated with a better film of lubrication. People choose different oil thicknesses depending on how hard the engine is being worked.
A crankshaft journal is the machined surface on the crankshaft that rides inside a bearing. The oil film between the journal and bearing is what prevents direct rubbing. When clearances are too tight for the operating conditions, the risk of metal-to-metal contact rises.
Metal-to-metal contact is when the bearing surfaces touch directly because the oil film is insufficient. In a healthy lubrication setup, a thin oil film separates the journal and bearing. When clearances, oil viscosity, or oil pressure don’t support that film, wear accelerates and bearing damage becomes more likely.
Bearings have two surfaces that ride against each other. Bearing surface pressure is how hard those surfaces are being pushed together—higher pressure can make the bearing wear out faster.
Dynoing is running the car/engine on a special machine to measure how much power it makes. Tuners use it to see what happens when they change settings.
It’s like how a stiletto heel concentrates your weight into a tiny area. In engines, the same idea applies to bearings: smaller contact area can mean much higher pressure and more wear.
Bearing delamination means the bearing’s surface layers start peeling apart. When that happens, the bearing can’t protect the moving parts anymore, and the engine can quickly suffer major damage.
The crankshaft is held in place by the main bearings. “Four bolt mains” means the bearing caps are bolted down with four bolts, which helps keep everything tight and stable when the engine is under stress.
This is another way of bolting the crankshaft’s bearing caps in place. More bolts usually means the caps flex less when the engine is revving hard.
Term
1.8 at 9 and a half thousand RPM
The speaker is describing an operating point at very high engine speed (RPM) and a clearance/fit target (“1.8” in context of the earlier clearance discussion). High RPM increases bearing load and oil-film demands, so the build details become critical.
The Ford GT40 is a famous race car that helped define an era of endurance racing. Here it’s mentioned as an example of building an engine and cooling system that could survive hard racing.
An intercooler cools the air going into the engine after it’s been compressed. Cooler, denser air helps the engine make more power and run more safely under boost.
A “four-valve” engine uses more valves per cylinder than older designs. That helps the engine breathe better, especially when you rev it.
Term
thermatic switch
A thermatic switch turns cooling on or off based on temperature. That helps keep engine coolant temperatures in a safe, consistent range.
Term
1030
“1030” sounds like a specific engine-building number (often tied to bearings or oil spec). It’s not a general term most people would know without the context of that build.
A billet alloy block is an engine block made by machining it from a solid chunk of metal. It can expand differently as it heats up, so the engine clearances may need to be set carefully.
As an engine warms up, metal parts expand. That expansion changes the gaps inside the engine, so the clearances have to work both when cold and when hot.
Oil pressure is how strongly the engine oil is being pumped around. It helps protect moving parts by keeping them lubricated, and it can change when the engine is cold versus hot.
Preheating means warming the engine fluids before you start driving. It helps the engine get up to temperature more smoothly so parts don’t get stressed by sudden cold heat changes.
Oil temperature is how hot the engine oil is. When it’s the right temperature, the oil flows and lubricates properly—when it’s too cold, it may not protect as well.
The cylinder head is the part on top of the engine where the air/fuel enters and exhaust leaves. “Development” means improving that design so the engine can breathe and burn more efficiently.
Porting means modifying the passages in the cylinder head that air has to travel through. The goal is to help air move more smoothly so the engine can make more power.
Flow bench numbers come from a flow bench test that measures how much air (or sometimes fluid) passes through an engine port under controlled conditions. These results are useful, but they don’t always translate perfectly to real engine performance because the engine’s airflow is dynamic and includes factors like pressure, temperature, and valve timing.
CFM is a way to measure how much air moves through a part, like an intake port, per minute. More CFM can be good, but if the air moves too slowly, the engine may not make more power.
Average port velocity is the mean speed of the air as it travels through an intake port, often discussed in feet per second. It matters because engine power depends on how quickly air fills the cylinder and how airflow dynamics behave through the valve and port; opening the port too much can increase CFM while lowering velocity, reducing effectiveness.
The inertial supercharger effect is how fast air moving into the engine can help pull more air into the cylinder. It’s not a real supercharger, but the air’s momentum can boost filling when the timing and airflow speed are right.
Bottom dead center is when the piston is at the very bottom of its travel. If someone says “after bottom dead center,” they mean the valve timing happens after the piston reaches that lowest point.
Term
valve open later into the compression stroke
The intake valve timing can be set so the valve stays open longer, even after the piston starts moving upward to compress the mixture. The idea is to use the moving air to keep getting more mixture into the cylinder.
Term
forced filling effect
A “forced filling” effect refers to using intake airflow momentum and valve timing to increase how much air (or air-fuel mixture) enters the cylinder. Instead of relying only on piston vacuum and overlap, it emphasizes inertia-driven flow that continues as cylinder pressure rises.
CFM is a way to measure how much air is flowing—basically a volume-per-minute number. The point is that you can’t just look at CFM; air speed matters too.
Mach limit means how fast the air is moving compared to the speed of sound. Designers try to keep intake airflow in a target range because near-sound-speed flow behaves differently and can stop improving.
Car
small block Chevy
“Small block Chevy” is a nickname for a popular Chevrolet V8 engine family. The hosts use it as an example to show how engine size and RPM affect intake airflow limits.
“Choking” is when the airflow hits a limit and can’t increase further. Once that happens, making the duct bigger or trying to push more doesn’t keep improving how much air gets in.
When air moves through an intake, the air right next to the walls gets slowed by friction. That “sticky” layer can grow and make the intake feel smaller, which hurts how much fresh air the engine can use.
Pressure drop is how much the air pressure falls as it travels through the intake. If the pressure drops too much, the engine can’t pull in as much air.
Term
RA finished texture
RA is a way to describe how rough the inside surface is, like how “smooth” or “textured” the intake port walls are. That roughness can change how much friction the air experiences.
Bernoulli’s principle is a basic airflow rule: when air speeds up, pressure tends to drop. That matters in an engine intake because pressure and flow speed affect how much air gets pulled in.
Air density is how “heavy” the air is. Hotter air is less dense, so even if you move a lot of air volume, there may be less usable air mass for the engine.
Turbulence is when the air doesn’t flow smoothly and instead swirls around. In an intake, that can waste energy and make it harder for the engine to get the air it needs.
Laminar flow means air moves in smooth layers without much swirling. The speaker is saying engine intakes usually aren’t like that—they’re more turbulent.
Skin friction is the resistance the air feels as it rubs along the inside walls of the intake. More friction means the engine has a harder time pulling in air.
EMS is the car’s engine computer. It decides things like fuel and timing, and it has to respond to what the engine is actually getting—especially when air gets hotter and less dense.
RA value is a number that tells you how rough a surface is, like a “microscopic smoothness score.” Port builders use it to aim for a texture that helps air flow instead of just polishing everything.
“Port and polish” is when someone cleans up and smooths the inside of the engine’s intake/exhaust passages. The point of this segment is that polishing can help in some places but can hurt in others.
Term
thermodynamic aspect
The “thermodynamic aspect” is about how temperature and heat transfer change how the gases move. In this segment, it’s tied to how exhaust flow can create pressure waves that help the engine breathe.
Kinetic energy is energy from motion. The speaker is saying that fast exhaust gas motion can “carry” energy that helps create beneficial pressure effects for the engine.
A “negative wave” is a pressure wave that creates a suction-like effect. If it arrives at the right time, it can help pull exhaust out and help the intake charge during overlap.
Overlap is when both the intake and exhaust valves are slightly open together. The idea is to use airflow and pressure timing to improve how the engine breathes.
Turbulent flow means the air isn’t moving in perfectly smooth layers—it’s mixing and swirling. The speaker is saying that, for intakes, that kind of flow can be helpful.
Term
trip that up
“Trip that up” here means you intentionally disturb the airflow so it transitions into a more turbulent, better-behaved flow pattern. The goal is to keep the air from just sliding along the wall in an inefficient way.
A “no slip” condition means the air right next to the wall is forced to match the wall’s speed (which is basically zero). The speaker is saying you don’t want the air to stick too much to the intake wall.
Term
40 grit to a burr finish
“Grit” is how coarse the sanding abrasive is. “Burr finish” means leaving a rougher texture instead of making it shiny, and the speaker says that roughness can help intake airflow.
Sound travels at a certain speed, but that speed depends on how hot the air is. In an engine, the intake and exhaust air are at different temperatures, so the airflow “wave” behavior changes.
The golf ball dimple effect is a drag- and airflow-management phenomenon where surface dimples change how air flows around a ball. By creating turbulence and tripping the boundary layer, dimples reduce the size of the low-pressure wake behind the ball, improving pressure recovery and overall aerodynamic efficiency.
Pressure recovery is how well the airflow “gets its pressure back” after it passes around something. Better pressure recovery means less of a strong low-pressure pull behind the object.
A negative pressure wake is the “suction” area behind something moving through air. If you can shrink that low-pressure trail, you reduce drag and it can go faster.
Port cross-sectional area is basically how big the passage is for air/fuel to move through. The discussion says dimples can change how that passage “works,” effectively reducing the effective flow area and changing how power comes on.
The valve guide is the part that holds the valve in place and lets it move smoothly. In the intake port, the guide can also disturb airflow and create turbulence.
Term
fuel off
“Keeping fuel off” means trying to stop fuel from sticking to the wrong surfaces inside the engine. If fuel wets the piston too much, combustion can be less efficient.
Dimple pistons have small dents in the top of the piston. Those dents can change how fuel and air behave during combustion so less fuel sticks to the piston surface.
The intake port is the channel in the engine head that air has to flow through to get into the cylinder. If the passage is shaped well, air moves more smoothly; if it’s rough or poorly shaped, it can get messy and turbulent.
The valve stem is the rod that the valve moves on. Because it sits in the airflow path, it can disturb the air and create turbulence if the port isn’t shaped around it.
In porting, shrouding refers to how the metal around the valve (especially near the valve stem/seat area) “covers” or guides the airflow. Proper shrouding can encourage the air to split and follow intended paths, reducing chaotic turbulence.
Eddies are little whirlpools in the flow—areas where the fluid swirls instead of moving straight. The idea is that the same kind of swirling can happen in an engine port if the airflow hits an obstruction.
Port drag means the air is being slowed down or resisted by the shape of the intake passage. If the airflow “wraps around” the guide and turns back on itself, it can create extra resistance.
A port is the passage air goes through in the engine head. Port volume is basically how big that passage is, and it changes how the air moves and fills the engine.
Optimal velocity means aiming for a good air speed through the intake passage. Too slow can reduce cylinder filling, and too fast can create losses—so tuners try to find the sweet spot.
Port energy is basically how “energetic” the moving air is in the intake passage. More energy can help the air keep moving into the cylinder instead of slowing down.
This is the idea that the air already moving through the intake can “keep going” into the engine, boosting how much gets into the cylinder at the right RPM. It’s like a temporary boost from airflow momentum, not a turbo.
Valve seats are the surfaces in the engine head that the valve seals against. If the seat shape is wrong, the valve can’t seal or flow as well, which can cost power.
Valve seat angles are the shapes/angles of the sealing surface where the valve sits. Changing the angle can change how air flows when the valve opens and how well it seals when closed.
Engine clearance is the tiny gap between parts inside the engine. It’s important because parts expand and move as the engine runs, so you need enough space to avoid rubbing. People measure these gaps very precisely, often in very small units.
Minimal cross sectional area is the narrowest part in the airflow path. That narrowest spot tends to limit how much air can get through. If you’re using online calculators, they may only be set up for imperial measurements.
A ported head means the engine’s head has been modified so the air can flow through the intake/exhaust passages more easily. The goal is to help the engine breathe better. Different porting methods can change how well that airflow improvement works.
CNC porting is when a machine uses a computer program to carve and shape the engine’s intake/exhaust passages. The outcome depends on how good the computer program is. People debate it versus hand-porting because the port shape affects how the engine breathes.
Hand-porting means a person manually reshapes the engine head’s airflow passages. The idea is that a skilled porter can tailor the shape more precisely than a one-size program. It usually costs more because it takes more work.
Core shift is when a cast metal part’s internal channels end up slightly in the wrong place. When you port the head, you may need to shape the opening to match where the channel actually ended up so air flows efficiently.
Airspeed is how fast the air is moving through the intake passage. Faster isn’t always better, but if it slows down too much near the valve, the engine can’t breathe as well.
CSA is short for cross-sectional area, meaning how wide the passage is. The key point is that the width affects how fast the air moves, especially near the valve.
If one cylinder gets more air than another, the fuel mixture won’t be the same in every cylinder. Equalizing airflow helps the engine burn more evenly, which can improve power and smoothness.
At higher RPM, the air moving through the intake has more momentum. The “velocity zone” is where the intake design keeps that airflow moving fast enough to help the engine breathe better.
A velocity gradient means the air isn’t moving at the same speed everywhere inside the passage. Good intake design tries to make that airflow more efficient and consistent.
CFD is a computer simulation that predicts how air moves inside the engine. It can be very helpful, but it only works well if the model is set up correctly.
Steady-state means the simulation assumes the engine conditions are constant, not changing moment to moment. It’s good for baseline estimates, but real engines are dynamic.
Engines breathe through tubes, and the airflow creates pressure waves. A “harmonic” is a repeating wave pattern, and the third one is the specific timing sweet spot that helps the engine pull in more air when the valves are opening and closing.
Like sound in a pipe, intake airflow can form repeating pressure waves. A “quarter wave” is one of the common wave patterns designers use so the wave shows up at the right moment to help the engine breathe.
When the intake valve opens, it can create a traveling pressure “dip” in the air. If that dip reaches the valve at the right moment, it can help pull more air into the cylinder.
Engines breathe through valves. If you close the intake valve at the right moment, you can trap more air in the cylinder and make the engine feel stronger.
Cylinder filling is how much “stuff” (air and fuel) you get into each cylinder. If you fill it better, the engine can burn more efficiently and make more power.
Induction length is basically how long the intake “tube” is before the air gets into the engine. Make it longer or shorter and the engine can make its best power at different RPMs.
This is a way of tuning an engine by thinking about pressure waves moving through the intake/exhaust. The goal is to shape the pipes so the “wave timing” helps the engine breathe better at the rpm you care about.
“Fourth harmonic” is another specific wave-timing target in the intake/exhaust. If the pipe shape can’t hit the lower harmonic they want, they may aim for the fourth instead.
The plenum is a chamber that acts like a reservoir of air before it goes into the intake tubes. Changing its size can change how evenly and how quickly air reaches the cylinders as RPM rises.
Supply bias is about whether the throttle feeds the plenum more toward one area than another. The manifold shape can make some cylinders get air more easily than others, so the plenum size has to be chosen to compensate.
A tunnel ram is an intake design that routes air through a longer “tunnel” before it splits to the cylinders. Its shape can help distribute air more evenly, which can let you use a smaller plenum.
Here, exchange rate means how fast the engine uses up the air sitting in the intake chamber and replaces it with fresh air. Faster replacement can help the engine breathe better at higher RPM.
Cylinder robbing means one cylinder can “steal” air from the others, so not every cylinder gets what it needs. A larger plenum can help keep pressure steadier so cylinders don’t compete as much.
This is about how directly air can travel from the throttle area to the intake tubes. If the layout lets each runner “see” the airflow path similarly, the system can be more balanced and may need less plenum volume.
A common plenum is one shared intake chamber feeding multiple cylinders. Because they share the same space, pressure changes can help other cylinders when one runner is in a low-pressure moment.
Rarefaction points are moments in the intake pressure waveform where pressure drops (a low-pressure region) relative to surrounding conditions. In practice, these dips can reduce cylinder filling unless the intake design times pressure recovery with the engine’s intake events.
In a carburetor, the booster signal is the “suction” that pulls fuel into the airflow. If the intake doesn’t create enough suction at the right time, the fuel delivery can get worse.
A shear plate is a small plate under a carb that helps fuel separate and fall into the intake runners more evenly. It also helps create the right kind of low pressure under the carb so the engine keeps pulling fuel correctly.
A single-plane intake feeds the cylinders through one main airflow path. With a big camshaft, the engine’s breathing timing changes, so the carb can struggle to feed fuel evenly—shear plates help fix that.
Reversion is when gases don’t just go the right way into the engine—they can flow back into the intake. That can hurt how much fresh air the engine actually gets.
“Torque on demand” means the engine gives you pulling power when you ask for it. The intake setup can be designed so the car responds faster when you open the throttle.
Term
trailing weight
In this context, “trailing” refers to airflow separation and swirl/eddies created by the throttle and intake geometry. Those flow disturbances can reduce effective airflow and therefore limit how much power the engine can make.
Term
Formula 1 went to barrel valve
A barrel valve is a throttle design meant to make the air flow smoother. Smoother airflow can help the engine breathe better at full throttle.
A common planum is a shared “air box” in the intake that feeds several cylinders. A good design can help the engine get steadier airflow and make power more smoothly.
Car
LS7
The LS7 is a high-performance Chevrolet V8 engine. The hosts use it as an example to compare different ways of feeding air to the cylinders.
The power curve is how strong the engine feels at different RPMs. Smoothing it out can make the car pull more consistently.
Term
off map
“Off map” means the engine is operating in areas that aren’t perfectly covered by the ECU’s main tuning charts. Tuning gets harder when you’re relying on how the ECU interpolates or extrapolates between those points.
The throttle body is the “gate” that controls how much air gets into the engine. Sizing it means picking the right opening size—too big can make the car feel less responsive, and too small can choke the engine and reduce power.
This is a measure of how fast the air is moving through the throttle opening. The idea is to pick a speed where the engine breathes well without the throttle body becoming a bottleneck.
Throttle sensitivity is how “touchy” or responsive the car feels when you move your foot on the gas. If the throttle body is too big, the engine may only respond strongly at the very beginning of pedal movement.
Instead of a cable directly pulling the throttle open, sensors read where your foot is and a computer tells the throttle what to do. That makes throttle control more precise.
The air cleaner is the air filter system. If it’s restrictive, it can limit how much air the engine can breathe, even if the rest of the setup is strong.
The Mustang Dark Horse is used as an example of a modern, very powerful Mustang. The discussion says that when horsepower gets extremely high, the intake system may need bigger airflow paths to avoid choking the engine.
Ferrari is brought up as an example of a supercar maker that used ITBs in the past. The point is that even exotic brands change intake designs to get smoother, more usable power.
Lamborghini is mentioned as another exotic brand that used ITBs. The takeaway is that even these cars eventually moved toward intake designs that make power smoother and easier to manage.
Runner length is about the shape and length of the tubes feeding the engine. The goal is to time airflow/pressure waves so the engine breathes better at certain speeds.
Term
small ARs
AR is a turbo design parameter that affects how quickly it builds boost. Smaller settings usually help the turbo come on sooner, but may not flow as much at the top end.
Inlet air temps are how hot the air is when it goes into the engine. Cooler air usually helps the engine make more power and run more safely under boost.
Turbo boost is the extra “push” a turbo adds to get more air into the engine. More boost usually makes more power, but too much can over-stress the engine.
A torque curve shows how engine torque changes across the RPM range. Tuning can shape the curve (for example, by delaying boost until after peak torque) to make power delivery smoother and reduce peak stress on the engine.
Precision turbos makes turbochargers used in performance cars. A bigger or faster-spooling turbo can make boost arrive earlier, which can be harder on engine parts if the tune isn’t adjusted.
The “air pump” idea means the engine’s main job is to pull in air. If you understand how air flows into the cylinders, tuning becomes more predictable even on different engines.
Fuel injection is the system that sprays or delivers fuel into the engine. Tuning it helps the engine burn the right mix of fuel and air for power and smoothness.
TDC means the piston is at its highest point in the cylinder. When people talk about “timing,” they’re describing when the spark happens relative to that piston position.
MBT stands for Minimum Best Timing, the ignition advance where the engine produces near-maximum torque without pushing into knock. It’s a tuning target because more timing than MBT can increase knock risk, while less timing leaves power on the table.
Flame front speed is how fast the burning wave travels through the mixture. If it burns faster or slower, the spark timing needs to be adjusted so peak pressure happens at the right time.
“Leaning out” means giving the engine less fuel than usual compared to the air it’s burning. Tuning it this way helps you learn how the engine reacts, but going too far can cause damage.
The exhaust valve is what lets burned gases out of the engine. Checking it after a run can show whether the engine was running too hot or not burning correctly.
Piston rings are small metal bands on the piston that help seal and keep oil under control. If they get “torn up,” it means the engine is wearing them out faster than normal—often because the tune or mixture isn’t right.
Car
4G63
The 4G63 is a Mitsubishi engine people commonly build for racing. Here, they’re talking about how they learned what works by running the same kind of setup, then tearing the engines down after a season.
Methanol is a racing fuel. In drag racing, it’s used because it can help you make a lot of power and it behaves differently than regular gasoline, so tuning and engine wear patterns can be studied.
This is the small gap between the piston and the cylinder wall. The size of that gap matters because the engine gets hot and the parts expand—get it wrong and you can wear things out quickly.
Ring end gap is the small space at the ends of the piston ring. It matters because the ring gets hot and expands—if there isn’t enough space, it can fail, and if there’s too much, it won’t seal well.
This means the fuel spray from the injector is hitting the inside of the intake instead of mixing evenly. If it’s too “wet,” the engine may not burn fuel as efficiently as it should.
A homogenized mix means the fuel and air are mixed more evenly. When they’re mixed well, the engine can burn the charge more reliably and make better power.
Injector timing means when the computer tells the fuel injector to spray during the engine’s cycle. If you spray at the wrong moment, the fuel may not mix or vaporize well, so the engine makes less power.
Port wall injection is aiming the injector so the spray hits the intake port wall rather than directly into the airflow/valve area. The episode argues this promotes evaporation and phase change (liquid to gas) before ignition, improving ignitability and power.
Carburetors mix fuel and air mechanically (without fuel injectors). The discussion is about how their fuel mixing can be good in some situations, even if injection is often assumed to be better.
The intake plenum is like a small “air box” feeding the engine. Planum/ plenum volume is how big that box is, and it can change how the engine breathes.
Injectors are the parts that spray fuel into the engine. If they’re too small or not tuned correctly, the engine can’t get the right fuel amount when you’re driving hard.
Turbo size affects how quickly the turbo builds boost and how much boost it can make at higher speeds. Bigger turbos can be stronger at the top end, but they may feel slower to respond.
LIVE
That engine, we ran at about 1.1 thou on the mains with a 1030 that ran that sort of
thousand-odd horsepower for near on seven years, and I actually posted the bearings
on online, and people were like, no way they've been in an engine, you know, that's how good
they were, but yeah.
Welcome to the HPA TuneIn podcast, I'm Andre your host, and in this episode we're joined
by Jake Bain from Bain Racing in Australia.
Jake specialises in developing cylinder heads and intake manifolds, and this is really where
I think science and art form kind of cross paths, there's so much that goes into developing
a cylinder head, and of course the intake manifold that's going to match it, and this
really can make or break the power that our engine produces, particularly if we're dealing
with a naturally aspirated engine where we don't have boost pressure to hide maybe a
poorly designed or poorly ported intake manifold and cylinder head.
This episode does get fairly down in the weeds, and there's a lot of complex topics that we
discuss, but Jake Fortunen does an amazing job of breaking these concepts down into plain
English so that we can all understand it.
We dive into the topic of air flow versus air velocity, what the difference is and why
it's so important, and this really comes down to why just making your ports bigger so that
they flow more air on a flow bench, doesn't necessarily mean that it's going to perform
when it goes onto the car.
We talk about the surface finish of the ports and what we need to know there as well as
port dividers around the valves themselves.
What we need to know, the dos and the do nots.
We also dive into the golf ball dimple effect and why that may or may not be the best option
to apply to your ports.
Interestingly all of Jake's cylinder heads are hand ported, and personally I would have
thought that in this day and age CNC porting would really be the only way to go, particularly
to do this at scale, but we get Jake's take on why he still prefers hand porting and why
this can deliver a better result than a CNC ported profile.
We also get into the world of intake manifolds, we'll find out about what aspects we need
to understand and how these affect performance such as the runner length as well as the volume
of the plenum chamber.
So there's going to be a lot of great information here to get our teeth stuck into.
Before we jump into our chat, for those who are new to the TuneIn podcast, High Performance
Academy is an online training school, we specialise in teaching people how to build
performance engines, how to tune EFI, how to construct wiring harnesses, we also cover
topics on fabrication, 3D modelling and CAD, race driver education and data logging just
to name a few.
You can find all of our courses at hpecamry.com forward slash courses.
All of these courses are delivered in high definition video modules that you can watch
from anywhere in the world provided you've got an internet connection.
This means you can learn from the comfort of your own place and you can learn at your
own pace.
All of our courses also come with a 60 day no questions asked, money back guarantee.
So if you purchase them for any reason at all, decide it wasn't quite what you expected,
no problem, let us know, we'll give you a full refund.
And for podcast listeners, you can also use the coupon code podcast75 that will get you
$75 off the purchase of your very first HPA course.
We'll put the coupon code in the show notes to make it nice and easy for you to find.
Lastly, if you like free stuff, then I've got a great deal for you.
We are constantly partnering with some of the biggest names in the aftermarket performance
industry to give away some great prizes.
You can always find our latest prize at hpacademy.com forward slash giveaway.
It might be an aftermarket ECU or dash, it could be some engine components or engine
building tools or just about anything in between.
They are great prizes and we will ship them free of charge to your door if you're the
winner.
There's no tricks here, no purchase required to get your name into the draw.
Alright enough with our introduction, let's get into our interview now.
Alright welcome to the show Jake, thanks for joining us today and like we always do with
our guests, let's find out about your background and specifically how you got an interest in
cars and more specifically our guest engines.
Yep, it was pretty much a family thing.
My grandfather was actually Don Bain, he was an Australian champion TT racer and he
was the head engineer for Valisette Race Bikes in Australia in the 1920s, 1930s.
He was also an airman in the Air Force so he was really, really big into obviously engines
and stuff like that and actually one of his privates was actually Jack Bratham.
So they become really good friends after the war when they come back and my grandfather
Don got him into bike racing and he got third place out at Mount Druitt there and then
he went off to Europe and got on into four wheels and ended up in Formula One but.
The rest is kind of herstry.
Yeah, pretty much, yeah so I was surrounded by cars from my grandfather to my father.
My dad was a panel beater and a frustrated mechanic so he was always, you know, I've
got photos at like three years old, I'm under a car, you know with him so.
Learning to tinker.
Yeah, it was going to happen.
So is it more an interest in cars that lead to engines or is the passion sort of driven
around engines from the get go?
Yeah, pretty much the science of engines, how they work and me just trying to, you know,
nut out what they do like people will try and simplify an engine to an air pump but
they're just there's so much more than that.
There's, you know, there's a science that we're still learning, you know, it doesn't
stop, you know, look at Formula One now, they've just cracked 50% thermal efficiency,
you know, doing little tricks like, um, motorcycle and all this sort of stuff, you know, so yeah,
it's um.
Yeah, we probably will never have a fully comprehensive understanding of everything
but I think that's one of the exciting parts about it.
There's always something new to research and something new to learn.
Before we get sort of too far into the engine side of things, what did your sort of childhood
look like and maybe sort of once you got to school and, you know, what's your education
look like at this point?
Where did you see yourself going in the future, I guess is the real question.
Originally I was going into arts.
My first business was actually a screen printing business at 15 so I was racing
BMX and doing all that sort of stuff and I was more into the arts because I was surrounded
by cars so I wasn't overly interested.
So I didn't leave school early, I went right through to year 12 so I stayed on and in that
time from about 16 to my 20s I probably built about 28 to 30 cars that I, you know, built
modified, sold on and just getting experience and playing with different systems and different
engines and yeah, yeah, all that sort of stuff.
And then I went into the trades late and did like light automotive engineering and then
went into advanced AFI and then started studying engineering online and doing all that sort of
stuff but I already had a really good understanding early.
My father was very much exposing me to engineering theories sort of from seven years of age,
had me all the encyclopedia and would get into engineering theories and chat and
so he was a very smart man for a panel beta.
Maybe panel betting and being smarter, definitely not mutually exclusive,
I probably add, we'll get all the panel betters listening offside with us if we don't clear that.
Yeah, it's the social expectation of trade guys, you know.
Yeah, yeah, absolutely. I think that's probably also shifting a little bit.
It's pretty clear these days you definitely don't need a university degree or a PhD to
lead a very successful life and I would also say that with the sort of fear at the moment of AI
taking over your job, it's going to be a fair few years I imagine before chat GPT is going to be
doing oil changes or a cam belt service on your car so probably pretty safe if you're in some of
the trades I would expect. Yeah, probably the safest industry coming into the next 10 years,
definitely. Yeah, absolutely. All right, so what did your sort of work trajectory look like? You
mentioned your screen printing business at 15 and then sort of getting later into the trade,
so yeah, fill us in a little bit. Yeah, so I went in to actually help a friend
in basically just general mechanics because I wasn't sure what I was going to do. I basically
had a side job sort of at home making money and then I got into that and then I was building
bikes at the time. I had a bike accident so I had a bit of time off there because I had to have
surgery and bits and pieces and then I wasn't sure what I was going to do and then I got offered to
run a shop out at Blacktown by a friend so I ended up going in there. I spent probably
two or three years there and I thought this is not what I want to do and I'd already started
a business sort of from home with my engines and stuff like that, doing engines for people and bits
and pieces from home and then I pretty much sort of branched out about 99, 2000. I was sort of doing
both so I was working through the day and then doing engines at night and on the weekend and then
I actually got into a shop probably in about 2000. Yeah, I started welding then as well,
so TIG welding because originally I was just doing meek so it was really hard to try and
test manifolds and build manifolds with a meek welder and steel and stuff like that but it gave
me a starting point and then once I got onto the aluminium because I was doing a bit of
subcontracting for a few different shops at that time so Ross Balancers was one I was helping a
fair bit with because he was building balances for our boat races and that sort of stuff.
I started doing a bit of subcontracting work for Ross and in the meantime I was jumping on
his TIG welder and learning how to TIG. Expending your skills the whole way.
Yeah, exactly and still doing a lot of engine stuff and obviously then I started helping Ross go
with balances and harmonics and stuff like that because we got right into that with the boats
and endurance races. The dampening effect really shows up quickly in engine bearings and stuff
33 minutes at 8,800, if the harmonics aren't right, you find out about it really quickly
where in drag racing you don't see that as much because it's very very short limited type racing.
Plus you're transitioning always through the rev range as opposed to holding at a certain rpm.
Exactly, exactly. I mean just a little side quest, let's just dive into that a little bit and I think
harmonic dampers are probably something that is largely misunderstood. I think the expectation
from those that just have a cursory level of understanding of engine building and machining
is you get the engine balance, we hear that term. So hence if the engine is balanced,
well why do we need, have harmonics? So let us know what we're actually missing here,
what are we not understanding? Well basically when an engine's revving it even at idle at
a thousand rpm, it's actually doing like 900, 1100, 900, 1100, every compression cycle as we
start to compress that air, the crankshaft slows down and twists up and then when the piston explodes
and starts to accelerate from that sort of 10 to 15 degrees after TDC, the crank speeds up again.
So we create a harmonic wave in the crankshaft which creates an amplitude and a frequency wave,
right? So that amplitude is what we're trying to actually dampen. I end up building the
test rig for Ross when he started bringing out all these metal jacket series and actually
testing what sort of frequency difference you'll see because ATI and Innovative West,
which we used to be a distributor for, they get right into this sort of stuff, especially
where you want it quiet. So if you've got an engine at eight or 9000 that sings
constantly, you don't care about how much noise it has at two grand, you want it quiet at that
point at where you're using it all the time. The other element that goes hand in hand with this
as well is where you have a resonant frequency and we need to make sure that we sort of stay
away or dampen out that resonant frequency. Is that correct? Yes, 100% and you'll get it
right through valve springs and everything like that. You've seen that in NASCAR when they actually
RPM limited their engines, they ended up right in a resonant spot and ended up costing them
engines because the spring wasn't designed for that RPM. They just pulled them from 9,000 I think
to seven and a half or something like that and they had all sorts of problems because now they'll
bang in that resonance. So in other words, you've gone to a lower RPM, which on face value would
seem to be an improvement for engine reliability and longevity, but now you're operating at a
resonant frequency so things are going to fail much, much faster than at a higher RPM.
100% that's right. Everything you're saying here sounds like a harmonic dampener needs to be
specifically tuned to the exact engine combination that it's running on and I mean just what you've
mentioned here sounds like even working out how to match a dampener to an engine would be very,
very complicated yet we have off the shelf options. So again, what am I missing here?
Yeah, it just comes down to how deep you're getting into an engine. Most of the balances
on the market don't do a great job at harmonic dampening. Factory balances will actually do a
better job and this is something I talked about with Roscoe, like he was supplying dampeners that
had a really, really hard rubber in it and I would say to him that a dampener needs to be a
sacrificial anode like your brake pads. There's no point giving me a dampener that's going to
outlast the engine, the bearings and everything just like there's no point supplying a set of
brake pads that are going to chew through rotors. We want that dampener to break down,
that means it's actually working, that energy's going into it and it's breaking it down so if
it's too stiff it's not going to dampen the harmonics and that's what we've seen on the test
bench. The amplitudes are too high which means we still have crank flex and that goes into the
durability and also the life cycle of the crankshaft. That's why now it's really,
really easy with a lot of the billet options out there because even if the harmonics are bad
we're not going to stress that crank terribly much but it's far more important in the old days
or now in certain race series it's much more important where they're really on the limit of
the engine. They want to get everything right. Okay, so there's a few follow up questions there
and this is a bit of a rabbit hole that we've dived down early but I'm here for it, it's interesting.
You mentioned you'll see this in the race boats in the bearings so if you've got a mismatch or a
dampener that is not doing its job, how will this show up on the bearings? Are you going to end up
with a bearing failure? Yes, yeah so the higher that amplitude gets in the harmonics, the more
the crankshaft starts to move around in the engine and it can start creating whipping in the crankshaft
and all sorts of problems so bearing degradation. We've seen this with years ago, I can't remember
the manufacturer but they brought out all these billet underdrive pulleys I think for Subaru's
and WRX's. It was like mid-2000s or something like that. Still pretty popular with those.
Yeah and they ended up having a lot of bearing failures from it because they've basically
taken all the dampening out of the engine. It reminds me years and years ago I had a turbo
B18C on my dyno, it's an old EG Civic and halfway through a run on the dyno, I just
heard this crack through my headset and immediately I boarded the run, shut the thing down and it
had fractured the oil pump, pulled it all apart, the oil pump was literally split in two and that's
a direct drive off for those who aren't Honda B series people, that's a direct drive off the
crankshaft and what we ended up sort of deducing had happened there, it was a result of a solid
front pulley instead of the factory harmonic dampener and when you sort of start digging
into that, that was quite a well known and understood failure mode so just again highlighting
the dangers of not having any dampening at all. Second follow up question to that was,
it sounds like, and I'm pretty sure this is exactly the case, these you see are sacrificial,
hence they are a wear item, what's the process here, how long between rebuilds or replacement for
the average harmonic dampener? It really depends on how severe the engine is, obviously the higher
we go up in comps, so once you start talking 15, 16 to 1 comp engines, obviously as you can imagine
we've got more amplitude because the compression strokes are higher and then so you get that slowing
effect on compression and the acceleration effect on the combustion. Yeah, yeah, yeah and
exactly and the separation becomes far greater, right, so then the balances work much harder but
generally most guys will get through a season with like the ATIs and they buy the O-ring rebuild kit
and stuff like that, the fluid dampeners they tend to last a lot longer, the innovative west type
ones, I've run a lot of them for a lot of years and they'd just go year after year because they're
silicon based ones so they don't wear, they just create heat and because they're an aluminium body
they just shed the heat, right? Okay, so on that note pros and cons between a fluid style dampener
and an elastomer based one? Much of much, they both have good points, there's some cheap fluid
dampeners that don't work well but the innovative west, if they've got it down, down part they're
really really good, there are science in themselves like how they've developed the silicon fluid and
the right viscosity and stuff like that, you know? Okay, all right let's get back to our main topic
now that we've parked a little side quest but building race engines, I'm just interested in
your take on this, how do you learn the skill and where I'm going with this to sort of broaden
out the question I'm really asking here, if you go through an apprenticeship and become a mechanic
there's elements of engine overhaul that you'll learn although let's be honest these days no
mechanic in a franchise dealership is rebuilding an engine, you don't do that.
So I kind of feel that on that front for the general mechanics it's kind of a bit of a dying
skill set, then we've got engine reconditioning as a career path and obviously yes there you're
going to learn about machining and building engines. I would wager that 95% of general engine
reconditioners are only reconditioning probably pedestrian car engines where specs,
clearances, tolerances aren't at the same level you'd need to be at when you're building an engine
that might be making 23 times the factory power level and revving 5000 rpm
higher. So first part, do you agree with that my take on that? Yeah 100%, yeah a hell of a lot
more work goes into like a recondition engine guys are spending 16 to 20 hours, a race engine can
be 40 to 100 hours and it comes down to and every series is different. I've been sort of lucky because
I've had my toe in you know endurance engines and drag racing you know like in a drag car you could
pretty much buy a set of springs and drop them straight in the cylinder head and run them where
an endurance engine you're deburring, you're sanding edges, you're making sure everything is
absolutely perfect because the thermal overload in an engine that does 30 minutes will be reached
where in a drag rap engine they won't right? They've warmed them up to 160 Fahrenheit roughly,
they run them down the track they're done. The springs won't overload at all where in a
circuit car or an endurance boat or something like that sitting at big rpm as you know every
time we compress that spring we're generating heat and then how they sit on the shim and how they
sit on the retainer, tiny little square edges that wouldn't be a drama in a drag car become a
problem in an endurance engine you know. Yeah I think I've sort of often thought to myself you know
making 1000, 2000 horsepower for 6, 7, 8 seconds down a drag strip sounds brutal but the reality is
as you sort of alluded to there, it's actually in a lot of ways more difficult to hold a lower
horsepower, lower RPM engine together over a 30 minute, 1 hour, 6 hour endurance race.
And then when you get into marine stuff it's just a whole different ball game because there's no way
in an automotive based application you're going to ever be able to hold wide open throttle
for 45 minutes in one go whereas that's very much the case for some marine applications correct?
Yeah 100% yeah thermal loads, coatings everything come into it then you know but like you said it's
that saturation time how much heat we're putting into it and even with compression ratios you can
over comp well pretty much all our drag engines are over comped you know you can run 14, 15 to 1
or E85 in a drag engine but you can't run or your limitations are sort of 13 and a half in a
working engine you know because we can saturate that heat into the cylinder head in 8, 10 seconds
but once we reach that saturation limit now we're starting to trip into detonation and hot spots
and stuff like that so there are other aspects we need to look at. So essentially what you're saying
there is with a higher compression ratio for an endurance application or even just a road race
application you're going to find that you're running into a detonation or knock limit which you
wouldn't see in an 8 to 10 second run down a strip. On that basis and again kind of probably a
little bit of a tangent to the main topic but with compression ratio it's one of those things where
I think it's really easy to sort of fall into the trap of more is better and I'm sure to a degree
it can be. I haven't been in a situation myself where I've had budget or capacity or time to
build the same engine with four or five different compression ratios being the only change then
dyno test them to actually figure the lay of the land out for myself and I think I probably am in
the same boat as the majority of performance engine builders. It takes a big budget to be able to go
through those things and actually find out. As you start getting up in the compression ratio,
maybe north of say 14 to 1, I'm guessing as well you get into the situation of the dome on the
piston can start interfering with flame front propagation so while on paper the additional
compression may be an advantage the reality is that it sort of becomes a moot point. Is there
any truth in that or am I on the wrong track? Yeah 100% especially with the old cylinder heads
that was a big thing and you see this now like we have factory motorbikes at 12.5 to 1. You couldn't
do that 20 years ago you know and that come down to the chamber design so and we have something
that we call surface area to compression ratio so the better the least amount of surface area to
compression ratio have the more stable the flame front will be and that's exactly what you described
the big lumpy top domes that we had before had a lot of surface area and the flame front had so far
to travel where now all the modern chambers like a lot of the Ford stuff we see there you know 37 cc's
really really small chamber and all the pro stock stuff now super super small chamber the top chamber
is the basically within a degree of the top seat angle we have a beautiful discharge coefficient
and the piston is almost flat yeah so we have a far better nucleus that kindling when it starts
at the plug can spread out a lot more evenly and we can get even pressure so we can also
get more torque for the same amount of bang because we're hitting the piston all at once,
it's not running across a dome and trying to you know expand from there so.
Are you getting, I might be a little off topic on a tangent here but are you sort of getting at
the point where this is going to depend on how much ignition timing you have to run if you've
got essentially a slow flame front propagation you're going to need to start the spark event
earlier on the engine cycle in order to achieve peak cylinder pressure at the optimal point.
So all of the build up and pressure that you've got while the piston is still coming up to TDC
on the compression stroke is kind of counterproductive, it's fighting against the piston, is that what
you're getting at? Yeah that also comes into play but just generally how much more surface air if
you think about say your big block in massive lumpy top piston and a big big chamber, 128 cc
chamber with a lumpy top say 13.5 to 1, if we redesign that chamber and make it a 90 cc chamber
and now flat top piston at the exact same compression the one with the smaller chamber will have less
surface area and it's that surface area ratio to compression ratio that creates the instability
in the flame front because it's got further to travel you know. Yeah that makes sense to me,
it's a tricky one because you can't maybe necessarily change a parameter such as combustion
chamber volume while keeping everything else consistent and my mind sort of, a lot of this is
difficult to discuss without the aid of drawings which doesn't lend itself nicely to podcasting
but hopefully everyone can follow along. Where I'm going with this is in my mind at least as
we reduce combustion chamber volume, particularly that dramatically, 125 down to say 37 cc as you
mentioned, that's going to have an impact on the valve angle which then affects port angle flow
etc so there's a huge number of knock-on events, is that correct? 100% yeah so the early stuff
you'd see like let's say talk small block shaft 23 degree, the closer we get to that you know 10
to 12 seems to be the sweet spot, pretty much everything's around that even your modern LS is
pretty close to it, all your aftermarket Ford big block even your 13 degree type small block stuff
that was when we really started to make you know we're making 950,000 horsepower in a you know on
430 cube type stuff but you could never do that with a 23 degree because they are a wedge head,
the chamber was horrible and that's why you needed to you know try and do every sort of trick you
possibly can to make it better but the port was very low, we had a horrible short turn so as we
stand the valve up we can also lift the port up as well you know. Yeah that makes sense.
Alright let's sort of come back to the original question and this is more around so how did you
build up this knowledge that you've obviously got a massive knowledge at this point and I'm
sure a lot of it has purely come from just being in there doing the work and seeing the results but
how did you sort of go from building garden variety engines to you know race engines?
Just who I got involved with just different people and I had fairly good success with
like you know straight strip engines in the 90s and early 2000s we were doing you know 11 second
hold and package type engines you know there were cookie cutter type engines but that makes
sort of 450 horsepower and you know they pretty much go 118 into 122 mile an hour in
in your comedores and stuff like that and then I just sort of went further and further at the
same time I was into a lot of boosted stuff and that teaches you a lot of lessons as far as
you know parts life valve quality piston quality ring quality and you know all that sort of stuff
so I fed that into the NA stuff as well you know because they work hand in hand people try and
treat them differently but the best NA engine is just an absolute brilliant boosted engine you know
A couple of points I'll sort of tuck in there at least from my own experience, having spent the
majority of my life dealing mostly with boosted engines, I kind of always relish the handful
of opportunities I've had to do work and develop a naturally aspirated engine. I feel that when
you're dealing with a naturally aspirated engine you've just got nowhere to hide, you can't fix a
lack of horsepower by turning the boost up to PSI. So in a lot of ways building a turbocharged
engine is in my opinion mainly around choosing components with sufficient strength to cope with
the power that you're going to be producing and if you can kind of do that the rest is,
I would say the rest, I'm very much simplifying this but it comes down to turbocharger sizing
and then tuning. Now yes once you start getting a bit further into it, it does start acting like
a well developed naturally aspirated engine out of turbocharger, it's going to be an even better
thing and to the point where if you start looking as well, my line in the sand was around the
relationship between inlet manifold pressure and exhaust back pressure in a turbo engine
for a typical street engine in stock form that might be 2 to 1 in favour of exhaust back pressure
and they do that obviously for response and with my old drag car we were just under that
1 to 1 so I had a little bit more inlet manifold pressure than back pressure and I kind of felt
and you'll be able to tell me if I was on the right track or completely out the gate,
I always felt that once you got that relationship below 1 to 1 then the engine started responding
more like a naturally aspirated engine particularly in terms of the cam profile you could select.
Yeah 100% yeah because now that overlap so our exchange rate is identical to NA
because the pressure differential between intake and exhaust is like it would be NA
and that's where a lot of people go wrong with boosted engines they look at them as additional
boost you know or boosted versus NA but that's why I talk about all engines are boosted by 14.7
pounds of atmospheric pressure all we're doing is changing that pressure ratio and like you said
once you start getting that intake to BP's around that 1 to 1 that's exactly what you're going to see.
Now for those listening to this thinking that solution to making heaps more power in their
street engine is just to put a bigger turbocharger on and get that back pressure down, well yes
you're right it will but just on that drag engine of mine that I'm referring to which was a 4G63
we didn't really see much in the way of usable boost pressure until 7000 RPM so on the street
a stock EVO would have probably dusted me easily. All right let's move on a little bit at what point
did you sort of you know really hit the ground running with your current race engine business?
Probably like 2002-2003 and at the same time we're starting to build some manifolds for some
you know big engine guys and stuff like that so they were really really good pretty much everyone
even today like some of the pro stock and super stock guys I work with they give me a ton of
feedback so like I say we can all learn together and that they've helped me dramatically you know
so yeah sort of from that sort of point I started getting a little bit more serious with engines and
bits and pieces so yeah one news ads and so the twin cam stuff and a little bit of push rod stuff
but I phased more into the for my building type stuff more in the twin cam
NA and boosted and then we went a lot a lot more serious with our manifold development in NA and
that's when we started to you know started breaking some records and bits and pieces and
you know top holding NA and yeah one news ads and yeah. Okay you've sort of alluded to a fairly
wide variety of applications for your engines you've sort of said marine drag strip obviously
street circuit you know how did you find these customers what are you doing to sort of market
your services to these to these industries? I never did they found me I don't know how but
people would walk in and say be able to man and yeah but it was really just word of mouth back
then. So reputation was everything? Yeah yeah that's it and I was pretty much a stickler for
you know clearances and stuff like that all my engines I wanted within two tenths of a thou
that was how I built them I also you know I built them on the tighter side of things rather than
the looser side and but at the same time I was on thinner viscosity oils because I wanted
more cooling I wanted more volume less pressure you know because as you know even in NASCAR
they used to turn oil pressure down just for qualifying right because people don't realise
that's a workload that takes away from horsepower right? Totally. So yeah even with our RBs now
we're still only on a 1040 and we've got people putting 60 weight oil in them and wondering why
they've got head drain problems you know. Okay let's talk about that every time you start talking
I find another topic that I want to dive into but the bearing clearance versus oil viscosity
is a pretty hot one. I've probably gone the opposite way in terms of building slightly
looser than a stock clearance and then moving up in oil viscosity and I think like a lot of engine
builders we tend to be a little bit superstitious, I started down that route, it worked, I didn't
have bearing failures and I pull an engine apart and the bearings looked like the day I put them in.
So on that basis Tic the box, happy with that, it's working, let's never ever change it.
So I'm not saying that my way is the only way but I guess the background premise behind that is
the crankshaft and even to the degree the engine block when it's on the workbench and we're building
it at room temperature is rigid, it seems absolutely rock solid. But the reality is when
you're pumping out maybe 1000 horsepower and revving to 8, 9, 10,000 RPM the crankshaft probably
resembles more like a noodle and even the block is flexing. So the idea is we open the clearances
out a little bit to prevent metal to metal contact between the journal and the bearing
and we make up for that lost oil pressure by going to a thicker or heavier viscosity oil.
Is there any validity in that given that your technique would appear to be the opposite way?
It's hard to say. So if you look at like pro stock and stuff, I think they're on like 0.5
oils now and down near like 1.2000, like super, super tight. You'd look at NASCAR, same thing you
look at. I would say there's a difference between a bespoke purpose built race engine however
and when we're trying to modify heavily a production block and crankshaft because
those engines can be designed with everything in mind so that the component will have
the required rigidity. So I don't know if that's kind of an apples with apples comparison?
Oh, 100%, it comes down to component strength. That's definitely like Cleveland's your best
example. Those crankshafts used to move around all the time. But at the same time, the more room you
give them, the more room they're going to move as well. So there's a two-part fold there. Like I
had guys building Cleveland's at three and a half hour blowing, making 1,000 odd horsepower. We run
them at 2.4 with 1540s and stuff like that and the bearings come out and they were just as good
we weren't giving away as much horsepower or seeing better life in valve springs and better
cooling and stuff like that. So I think that people just play it safe, run a thicker oil
and bigger clearance. That's exactly what I would say I'm doing. I think it's also horses for
courses like NASCAR or ProStock go where a few horsepower could be the difference between qualifying
on the front of the grid and not. Sure, I get that. Whereas when I'm drag racing and I can turn
the boost up another quarter of a PSI if I want to make another 10 horsepower, I sort of weigh
that up where what I prefer to sort of play it safe. That's kind of where my mind sits on it.
Yeah, the other balance is there is bearing surface pressure. So from like 2000 or 3000,
we increase the surface pressure by about 80% even though it's only a 33% increase in clearance or so.
So and now we're seeing that in RBs. So like I talked to the fuel that guys con from
CRD and all that and like he was actually dynoing one of my engines and I think they're up around
190 psi all pressure to keep bearings in these things. Yeah, like massive, right? Holy shit.
And he rang me and goes, man, this engine's only got 75 psi. I said, man, that's tons. It's 1040
and the engine's like 1.8 thou and we're doing 8000 rpm. That engine's done seven years now.
The bearings like they've cooked cylinder heads on it, tuners and detonated the engine, everything.
And now you're seeing a lot of them need to go to a wider journal because that's the other
drama. If we go from 2000 or 3000, we're increasing that surface pressure. That's the
latter heel theory. We're reducing surface area. And this is where you're seeing a lot of people
getting in a trouble in the boosted game, you know? I think that's probably an aspect of the
increased bearing clearance that a lot of people just wouldn't actually put into together and think
about that. So I'm glad you raised that actually. Yeah, well actually a female engineer founded in
the 90s in Nazca. They started eating engines. I run in 3000 and she explained the stiletto heel
theory. I can't remember her name, but I remember getting told the story by a good Yankee friend
that I was talking to. And they actually reduced the bearing clearance and all their bearing problems
went away. So we're seeing a few guys now at 2000 odd horsepower with bearing delamination
problems. And I tell them, I said, pull four tents out of it and try it. And sure enough,
they pull a bit of clearance out of it and their bearing problems go away. So yeah, it's a dance.
Yeah, of course, of course. I think like anything, it's difficult to have a black and white rule.
On that basis though, this probably isn't a rule. It's more of a rule of thumb,
which has always been that in imperial units, about a thou of clearance per inch of journal
diameter is at least a sensible starting place. Does that still hold true? Yeah, I run about
probably 0.7 to 0.8 of that. But again, like you said, it comes down to, if you've got a 4340
crank, it's super strong, you've got a nice rigid block, you've got four bolt mains or like with
the one new Z stuff, they're all six bolt type stuff. As I said, I run them at like 1.8 at
9 and a half thousand RPM. A really great example of this was the GT 40 we did. I think in 2005,
2006, I think it was one of the world's fastest mark two when we did it. And it was the first
of the we designed between me and Bobby, the owner, we designed a AC based cooling system.
So I built an intercooler in the back, we had a radiator up the front that flashed 90% of the
heat off, then it come into the cab and went into the box where we had the evaporator inside the car
and ran some copper pipe and then it went back out. And it actually worked far better than I
thought it would. So it ran around 19 PSI made a thousand horsepower was the 4.6 Cobra engine,
you probably know it. That was sort of Ford's introduction into the four valve and now they've
got the coyotes and stuff like that. So it was pretty much that generation one, the Italian block,
the really good block. We were seeing 16 to 18 degrees, rain, hail or shine on that. It was
so stable because we had a thermatic switch in it so we could control water temperature.
Yeah, it was really, really efficient. It actually blew me away. But that engine we ran
at about 1.1 thou on the mains with a 1030. It did seven years of racing and street driving and
he was very hard on the circuit. So it did about 40 to 50,000 K's. We pulled that down in the
bearings or like brand new. But you know, I thought it had a forge crankshaft from the factory. We
run the forge crankshaft. We put a good set of rods, put a set of mild pistons in it and pretty
much everything else was standard other than ARP kits. But as I said, it ran that sort of
1000 odd horsepower for near on seven years and I actually posted the bearings online and people
were like, no way they've been in an engine. That's how good they were. But yeah.
Yeah, it's nice when they come out looking that good.
Yeah, so now I've definitely pushed the limits on clearance to see sort of where they bite me
and I haven't found that.
Of course, if you find that point, it ends pretty badly and pretty quickly.
Yeah, yeah, well that's just dying isn't it?
I guess it's worth mentioning here that this all sort of goes hand in hand with a really good
quality oil. But probably goes without saying no one's going to be putting sort of a cheaper
repco mineral grade oil in an engine that's built to that sort of spec. So in terms of
the bearing clearance before we move on as well, I'm going to go out on a limb and assume that
you've also had plenty of experience in billet alloy blocks.
A little bit, not as much now. So probably a handful of billet alloy blocks and probably
more in the boat scene than in like RBs and stuff like that. So we've done a few in them.
The reason I ask is there's sort of been a bit of debate. It might have settled down over the
last few years. We kind of instigated it with an interview that we did at World Time Attack
a few years back where basically it was an argument that a full billet block really isn't
streetable. And Darren from Bullet Race Engines kind of took offense to that because he's got
plenty that are in street cars. So fair play. I guess where it comes to is the problem with a
full billet alloy block is that the growth as it comes up to temperature is significantly higher.
So you either have a very very tight bearing clearance at room temperature which can be
potentially dangerous until it heats up, or you put up with excessive clearance at operating
temperature. Can you add anything to this, what's your take on that and which way should we be going?
Yeah 100%, you really want the alloy stuff tight and that was even with Bob's GT40,
they're a full alloy block. Hence why we run them so tight. Like I said, I think we're around
about that on the mains 1.1, 1.2 really, really tight because the block will grow three times
faster than an iron block and three times bigger. And we've seen this with Paul Madill's stuff in
the boat racing. So he was racing the 600 cube twin turbo full billet block type deal and there
a four minute race. Those engines were going together at like 1.2, 1.3. They'd start off with
110 psi oil pressure and finish off with about 20. That's how much the block would grow away from the
crank. So that's definitely a thing. But yeah, we've got a couple of guys that street drive them
and they seem okay. But as I said, they're tight and you definitely need to dry something with them
trying to use a factory pump. You just don't have the volume. You really need the volume.
I think a lot of it comes down to education and understanding what you're dealing with.
And of course if you've got the time and the inclination, there's nothing to stop you preheating
the oil and coolant as well. And this sort of comes back to Formula One style engines where
people think that they can't be turned over at room temperature. Obviously complete nonsense
but they do need to be pre-warmed before startup. 100% yeah. And common sense and just educating
customers. This is why I sort of went away from the street guys and went to the race guys really,
really early in my business because I just found that the street guys always have an answer. They
always know their mates always know where the race guys, if I say you're running this oil,
you warm it up to 80 degrees before you take it to this RPM, they just listen because
they've broken enough engines and they've got enough experience to know they don't know and
they'll just listen to the engine builder you know. And let's be honest, this shit is not
cheap as well. No that's exactly right. So any of the alloy guys I tell them, I don't care what
you do to it, you drive it as hard as you like but get it warm. I want the oil temperature at 70
degrees, I want this, I want that. And then once it's at that, do what you like. I'm interested
in your take on this, obviously running a successful business building race engines.
I kind of always wondered if it was a smart business model, so not trying to insult you.
I went through the same but you're building an engine where every part that goes into that
engine is expensive. The margins that we as the shop get off these is usually very small or often
the owner wants to bring you the parts himself which is never great. So you're going to make a
little bit in margin on the parts, a little bit maybe on the machining and then obviously there's
your labor. So the odds are really stacked against you because it's only going to take one single
thing to go wrong and that can be a complete walk away loss and then it's up to you to rebuild it.
Any take on that? 100% yeah, it's a labor of passion and you always end up putting more in
and you talk to anyone like all the guys I know, the best porters in Australia and the engine
builder, the same thing. They're putting in way more hours than they charge, so it is definitely
a labor for passion but also it comes down to choosing the right customers. I know that sounds
arrogant but you really need someone responsible if you're doing that. I noticed that once I
transitioned from street guys that would just go to the local cul-de-sac and hold it on the
rev limiter doing donuts all day versus a race guy that wants to win. So since I transitioned
into that, 99% of my stress went away. I think that your success is often dictated by the jobs
you turn down or the customers that you fire. So yeah, I couldn't agree more with that.
I think so 100%. I think I know we talked about advice for new mechanics and other people starting
their business but the customer isn't always right and you really should select the right
customer for the right job. You can say no. It's hard to say no to work particularly when
there's dollar signs hanging over that particular task when you're fresh and new and you're hungry
to make rent payments. So it's difficult to start with and I think every business goes through the
same trajectory. Originally you'll take on anything that comes through the door and after
hopefully only a year or two you start realising that that's actually not the smartest way to grow
your business and get a reputation. Yeah it almost took me a decade but yeah.
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out the full VIP package and everything it contains. Alright let's get back to the episode.
Let's move on, what I really wanted to talk about, we've wasted 40 odd minutes at this point,
I wouldn't say wasted, it's been a great chat but on SideQuest, now again it's the meat and
potatoes of this interview which is really around cylinder head development and later
we'll talk about intake manifolds as well. Now this is an area that I have never personally
got involved with. First of all, it's fiddly work and I don't like hanging on the end of a
diagram for hours and hours on end and then you sort of get to the situation, you've done a great
job on one port and you're like, ah shit now I've got to replicate that on another seven,
that's tough. So I've kind of left this to those who are good at it and I think probably
most people do but you're one of the people who is good at it. I think when it comes to
porting cylinder heads, there's a misconception that bigger is better and particularly you see
this thrown around when people start quoting flow bench numbers and obviously something
that flows 300 CFM has got to be better than 200 CFM. So where's the disconnect here and why is
that not the case? The disconnect comes down to velocity and the dynamic motion of the engine so
by that I mean the cubic capacity and how much velocity is going to drive through that duct.
A flow bench will not tell us what the right size is for an engine, it'll only tell us how big that
port flows and anyone who's been on a flow bench will go down this rabbit hole, my probably my
first 10 years on a flow bench was chasing flow figures and then realizing why they didn't make
horsepower because you can make that, if you keep making that hole bigger it's going to flow more
but that doesn't translate to horsepower and it doesn't translate once you start understanding
average port velocity. So if you've got a really big growth rate from your valve to your window,
it might look good on the flow bench but then if you start doing some math and you start calculating
how much air velocity you have at the window versus how much air velocity you have at the seat
and then the average velocity, a good port in two valve is going to start at about 270 feet per second
and go up from there and a good twin cam is going to start at about 300 feet per second and go up
from there. So as you can imagine the bigger we open the window the more our average drops
as far as velocity goes. Which is still limited at the valve by the diameter of the valve and
the valve seat correct? Yes but let's say our valve is two square inches and then we've made
our window three square inches. Well if the valve is two square inches and flows 300 CFM,
300 feet per second sorry, then the window is only going to do say 200-ish. So now if we add those
two together and divide them by two now our average is only 250. So we've actually made the
port go backwards even though we've seen more CFM on the flow bench because we're not looking at
that velocity aspect. Okay cool right let's dive into that a little bit deeper. Why is velocity
so important? Velocity is what creates our inertial supercharger effect and I try to explain this to
a lot of people that air has weight and the faster we drive it and the greater the average
in the port the more weight it has to push and fill that cylinder because people forget the
filling stage isn't on the downstroke of the engine. Most of our inertia is working as the
piston's coming up the ball that's why we have timing after BDC and even factory engines will
have 50 degrees after bottom dead center. So if we've got more velocity and hence more inertia
that would allow us to hold that valve open later into the compression stroke and get that
sort of forced filling effect? Yes yeah yeah exactly. Okay and I think that's an aspect of air
and airflow that again for those who who've really never delved into it the inertia aspect or the
fact that air has a mass is something that's quite foreign. It is actually right because it
feels like nothing. Yeah but it does in fact have mass. Okay so we've got these two kind of competing
metrics air velocity and we've got our cubic feet per minute, our air flow. How do you then kind of
balance these two out and just not go out chasing bigger CFM numbers when you know the
velocity and how do you size this to a specific engine or application? We target to its Mach limit
so it's dynamic. So what we do is we calculate what the running engine would need and generally the
limit is anywhere from 620 feet per second to 710 feet per second. So it's like 0.55 Mach to 0.6
Mach and that's basically a division of the speed of sound 1116 feet per second if we just times
that by 0.6 that'll give you an air speed right. So what I'll do is calculate what the minimal
cross-sectional area is in that engine and that's the restrictor. So if we've got you know a four inch
ball by three inch stroke like a small block Chevy or something like that or 350 stroke and we're
saying 8000 RPM then we'll calculate what the minimal cross-sectional area needs to be before
the engine chokes. So we size that duct to match the peak RPM. So that way we know we're getting
as much air speed as we possibly can before the point of degradation right before we start choking
the engine. So in other words we're trying to create as much force as we possibly can
to keep pushing air in as that cylinder pressure rises and you can feel that pressure if you put
your hand out the window just even at 100 kilometers an hour you can feel how much pressure you
feel on your hand. Now times that by six or seven and that's roughly what we're seeing in an intake
port and it's that inertia and that velocity that continues to feel the engine as the piston's
coming up the ball. So yeah. What drives that limit of I think there was a 0.6 basically why can't
we just go higher and get more inertia? The physics of air so it comes down to the boundary layer
and the pressure drop. So at say let's say 600 feet per second I think we're around about nearly a
PSI pressure drop. So it's a balance between density and velocity and as well as temperature.
So the higher velocity we have the more boundary swell we also get. So that's another aspect because
as the air velocity starts to increase the boundary layer will expand in the port. So we start to
reduce the cross-sectional area. This is why RA finished texture in the port is so important
getting the right texture and stuff like that you know. Okay okay again every time you answer
one question you just bring up another three or four questions that need to be covered off.
So yeah okay boundary or actually no let's come back one step. So this is sort of Bernoulli's
principle as velocity comes up increases pressure drops. That's what you're talking about with the
air density actually reducing. So you sort of get to this point where you could increase the air
velocity but the reduction in the air density kind of cancels it out. Is that what you sort of
getting to? It's a multitude of things because you've got boundary layer as well reducing the
cross-sectional area. Yeah because yeah the boundary layer is actually changing the cross-sectional
area but and the higher the velocity we get the more engagement and the more friction we create
in the boundary layer and in the air stream. So you start intermixing because a lot of people
think intake's a laminar flow they're all turbulent. It's about how we can minimize the
turbulence and minimize the skin friction in the port. That's what we do as porters or engine guys.
How gently can we get that air in the port and how fast can we get it in without cooking the air
because as we increase velocity as well and the boundary layer starts to thicken we start getting
more convection. So now not only are we choking the engine as far as the whole size starts to reduce
but we're starting to lose that density in as far as air temperature. So air temperature starts
to spike and this is where you'll see engines just fall off the dyno because now the mass
disappears. You might be getting the volume in but you're not getting the molecular density in there.
Right? Yeah yeah it's the EMS that we need, not just volume. 100%. All right now let's come back
to boundary layer. I mean it's probably a bit of a hint in the name. I imagine most people can
probably pick up the pieces and figure out what a boundary layer is. But you mentioned the surface
finish, roughness, average RA value for your port wall and I think again those who are new to it
and I certainly had this opinion back 25 years ago when I first got started out that a mirror
smooth finish, and I think this probably comes from the old term port and polish. So a mirror
smooth finish on your port wall surely is the sort of the go-to option, not the case. What do we
need to know? Definitely the worst thing you can do is polish. That belongs in the exhaust so we
need to understand that the intake and exhaust are two different environments. The intake is very
cold, wet and sticky and it has a very low mach limit so we can only accelerate air so fast at
like 600 feet per second where the exhaust is very hot, dry and smooth. We have due to air is
affected by temperature more than anything as far as its speed limitations so if we've got super hot
gas we can flow far greater velocity factors even though the mach index will stay the same
but we've moved the speed limit from 1,100 feet per second to maybe 2,000. So now we can do
12, 13, 1400 feet per second in the exhaust. So this is why we want a mirror polish in the
exhaust and the other aspect that feeds into the exhaust is our thermodynamic aspect because
kinetic energy is heat so the less convection we have into the cylinder head the more that
velocity carries out the engine the more we can use that inertia on the exhaust side of things
to send a negative wave back into the intake to help overlap and stuff like that. But yeah on the
intake side because we're dealing with a cold gas and generally in a wet environment
if it's carbureted or fuel injected or whatever it may be we want an active boundary layer
in most turbulent flow regimes anyway we want to trip that up we don't want a no slip regime right
we don't want it grabbing on the floor what we want is like little ball bearings and making
the air slip and trip over itself so we need a certain amount of RA texture
and the optimal range seems to be between 100 and 200 from our testing and everyone I sort of
talked to around the world and that's that's probably like a 40 grit to a burr finish.
Okay that's actually quite rough. Yeah yeah yeah I'm glad that you related that to a grit because
most people won't, an RA number is probably pretty meaningless to most people. 100%.
I guess like one thing I just wanted to kind of add to that when you're talking about the exhaust
and the speed of sound we just need to understand for those who aren't aware that's heavily related
to the temperature so that's why it's dramatically different between intake and exhaust. That's
right yeah. Alright so if we're talking about the port finish and the intake this probably comes
to the inevitable conversation about the golf ball dimple effect which has kind of
been, it's come, it's gone, some people swear by it, others ridicule it.
Yeah I'm on the fence here, I've never tested. What's your take on this?
It defies physics so if we understand what it does on a ball basically the whole point of a
dimple is to create more turbulence, a thicker boundary layer and trip the air even more to turn
around the ball and this helps with the pressure recovery of the ball and also reduces that negative
pressure wake behind the ball. That's what makes it go faster and you only need dimples
at our separation point. You don't need them all over but a ball spins so we have to put
them all over right? Of course. So what a golf ball is doing is sacrificing more skin frictions
and more surface drag for that reduction behind the ball. It's actually the parachute that negative
pressure pulling on the ball that stops it flying much faster so the dimples don't help it directly,
they help it indirectly by reducing the wake behind that negative pressure and also they reduce the
negative pressure behind the ball so you don't get as much negative pressure behind the ball so
the pressure recovery is much higher with dimples. So in a port aspect there's no behind the port
so all we're getting is a negative aspect. We're getting more drag, we're getting a thicker boundary
layer and that's what it shows on the dyno, they just sign off. What a lot of people have been tricked
into is they've had ports that are too big, they dimple them and it worked for them.
So effectively we're reducing the port cross-sectional area with the boundary layer?
100% right and and you'll see that but they still narrow the horsepower curve because while
velocity is low the boundary layer won't swell but then as it starts to come in then it peaks
much quicker and then chokes the engine off and pretty much me and everyone I know that's tested
this has seen the same thing. So we can sort of throw this in the burn and call it junk science
it's just marketing hype doesn't work? Yeah definitely yeah yeah the only areas that I can
see at work is in real low velocity areas. If you've got a really really bad port and I've had this
discussion with a few people like behind the guide where the bowl is right. If you dimple that
you'll see some improvements but then at the same time if we fill that shark fin it
fix the turbulence that wrapped around the guide and caused two crashing waves into each other
and done a nice tail fin in the port then not only have we reduced port volume so we've increased
port velocity now we've made it better all around. So like it's a band aid that you can use but
there's other ways to do it. Do you see better to fix the actual root cause of the problem
rather than try and tuck a band aid on it? Yeah but where I would say it can work is on pistons
and inside a chamber where the boundary thickness is an elimination of flow that keeps fuel off.
So you'll see this with I think it's what is it air of piston the diesel manufacturers and stuff
they're starting to do the dimple pistons now. I haven't seen any ABA testing on it but as far as
the physics go a thicker boundary layer on top of the piston will help keep fuel off it. So technically
by the physics it would work but we'd have to see a proper ABA test. So we used to use it inside
chambers in the early 2000s where we'd see a bit of wetting it was just poor chamber poor valve
angle. Now with better chambers there's no need for it but in the early days we used to do little
corners of the chamber and I think even GM performance actually released some of their
performance engines with dimples on their pistons which they showed I think three or five percent
better fuel economy you know. Yeah definitely a bandaid. As part of that you just mentioned
sort of a shark fin around the guide. This is another part that I wanted to talk about. A lot
of my experiences I guess predominantly were four valve import style cylinder heads and it's
quite often that the guide will be completely cut away to the port wall and just port it as
part of the intake port. Is this viable? Does this work or are we better to profile the guide
and maybe the cylinder head around the guide? Yeah you're definitely always better to profile it
because think about it if we take it out then we have this you know telegraph pole standing up in
the middle of the port velocity as the air comes in it's going to crash into that valve stem. So
the more shrouds we can put around that stem and the earlier we can tell the air to split and you'll
see this even in pro stock with floor fins so we have a roof fin and a floor fin. Same thing what
we're trying to do is thin the density out as it comes towards the guide so the guide the valve
stem sorry doesn't create as much turbulence in the port because what we're trying to do is
really we're trying to reduce any wrap around turbulence any we're really just trying to
manage how much turbulence that port has and reduce every aspect we possibly can. So yeah I've
done it in the early days I've designed billet heads with with actual valve shaft fin type bosses
in them they look better on the dyno they look better on the flow bench and they'll have less
cc's so for instance you'll knock that out and you might knock two or three cc's out of the
twin cam port right knock the divider down grind the guide down but when you look at flow figures
you you have to compensate for the increase in volume it's same as when we put a bigger valve
in if we put a 10% bigger valve in but we only make 5% more flow you actually went backwards
sure you know what I'm saying so even with that that guide if we can shape it and try and help
the air get around the guide properly and especially even on the backside so it doesn't
because it's going to wrap around it you see this if you watch a tide come in there's a
pole in the ground you'll see those eddies behind the pole right behind the pier and that's why you
see even now when they design bridges they're designing them like a long taper almost like a
sharp fin right so the water is more streamlined past these that way that they don't get as much
degradation on the concrete on the backside because that turbulence eats them away
same thing with the port if we can put a nice fin on the other side as the air wraps around the
guide it now has a guide to go into the port not wrap around back on itself and create more port drag
so there's definitely an aspect and it keeps our port volume even smaller because the best port in
the world has no dead areas and this is what we're trying to accomplish and we can never ever get it
perfect and once you start this is why you'll see ports have gone from rectangles with small
radiuses to big ovals now right because if you have two converging sides so a roof and a wall
those two sides are going to create drag on each other so when you probe that corner if you've only
got a little 58 radius sorry 15 16 so an eight mill radius you'll find that corner is dead
so when we probe a rectangle port we'll get this nice little oval of nucleus flow where it's actually
flowing so that tells you you can pretty much close that whole port up and just make it a nice
oval now no reduction and flow yeah now we've got optimal velocity we might even see better flow
figures on the flow bench and we've reduced the volume so now we have more port energy which is
going to help carry that inertia supercharging effect we're talking about because the average port
energy feeds into that so yeah look if there are only two or three mill I'll take them out but if
you know I see people cutting seven mill out of them and I think man just shape it and you'll
do alright but yeah okay valve seats this is another area that there seems to be a lot of
debate over what's best you know how many angles should we have to the valve seat should it be
radius what can you tell us about the importance of the valve seat because it's sort of some people
will say that's kind of the make or break to the performance of the head yeah all inductions have
what I call area of priority and it all starts at the valve seat so the most important area of
any cylinder head is the valve seat the least important area is the throttle body right and
that's the so if we're going to do anything so gains versus horsepower sort of deal if we had a
really really bad seat that might cost us 20 30 40 horsepower right oh well yeah if we had a bad
entry or bad radius say we had a 5 8 instead of a half inch or something at the plannum that might
only cost us eight horsepower so it all starts at the valve seat that's the most critical and the
further we get away the less critical it is so yeah definitely. Somewhat a relevant question but
just for my own interest you're based in Australia and you've consistently throughout this interview
so far used the the imperial system for measurements how do we get to this point? I use both because
a lot of the engine calculators and even going back to what you said about you know engine clearance
you know an inch per thou and stuff like that so a lot of the rules and a lot of the engine
calculators are all in imperial so I always learn both and I tend to talk in both metric and imperial
but I think on this side of the world I 100% agree with you, on this side of the world we're
kind of forced into using both because at some point you're going to be sourcing inevitably sourcing
engine components out of the US and of course the US is an imperial measurement system so hence
yeah you kind of, you shoehorned into it, I was just having this debate with our motorcycle engine
guy Luke who's currently writing some motorcycle engine building content for a course that's coming
up and he's been going through my automotive engine course where I do use the imperial system
and he's like what's wrong with you, why are you doing this? Because in the motorcycle world
not so much as it turns out yeah anyway I mean as long as you know how to convert between one and
the other it really doesn't matter in my opinion. Yeah that's it, 100%, you've got to live in both
but like I said a lot of the calculators especially that minimal cross sectional area,
they only work in imperial so you can't put a metric, I've got calculators that I've converted
and now that will work on both but generally if people are looking online they have to use
imperial sizes but yeah. The actual logistics of creating a ported head and the old days it
sort of comes back to what I was talking about that I despise hanging on the end of a
diagrinder, I can only assume these days everything's being CNC ported? No all my
heads are still hand-ported. Interesting okay yeah a hand-port will beat any CNC head on the
planet and we guaranteed that and it simply comes down to cost versus reward, obviously hand-porting
there's far more work that goes into it but there's also customization that goes into it
where CNC it's only as good as the program. Of course yeah and like RBs and stuff like that
we make around 45 to 50 horsepower more at the same boost over a CNC RB head
and earlier boost thresholds because we have better velocity right? I guess my argument on that would
be cool, why can't we take your port that makes 40 to 50 horsepower more than a CNC port, digitize it,
replicate it and put that on the dyno and we should be there? Yep no.
Okay and the reason why is Duke comes down to core shift and things he needs to over cut
so they're generally bigger and cross-sectional area and lower on airspeed so where it really
really works is in the aftermarket industry where we cast a head small and we put the right size
CNC port in then you're winning like it's that's you know that's NASCAR pro stock everything will
do that a lot of guys will just hand finish them but you'll see when they cast a head they cast it
just with a thumb hole from the valve seat to the window and now we can put what cross-sectional
area we actually need but the drama with OEM so RBs, 2Js especially that 90s era of twin cam is
a lot of them were already on the larger side so RB26 for example the minimal cross-sectional
area in an RB26 doesn't start choking to 9000 rpm dead stock so when you're porting it what we tend
to do is just attack the areas that need improving but also compensate for the core shift so we don't
have to make the bowls bigger we don't have to make the whole port bigger so we can have a smaller
port and even less CFM so my hand ported ones flow about 285 CFM and some of the digitized ones that
helped with flow about 300 CFM same sort of port but my ports only 130 ccs and their ports like
138 ccs and this is why they'll make more horsepower but even with the core shift say we've got a little
core that goes left and then in the next bowl it goes right I can port and keep my cross-sectional
area the same even though it kicks a little bit left and it kicks a little bit right it might only
be 1 or 2 degrees but 1 or 2 degrees isn't going to affect velocity because velocity is controlled
by the CSA but if I just go and hog that bowl out to where the core shift is rather than you know
fudging it a little bit now my velocity might be 10-20% lower at the valve seat and then that's
where I'm losing the energy. Sure yeah OK that's a really interesting take on it. I guess from my
perspective not being directly involved with this I would have assumed that one of the advantages
with the CNC port profile is that and again I might be completely wrong here that each port is
going to be able to flow exactly the same hence you're getting a more consistent airflow into
each cylinder. Obviously a lot of this is still driven by the plenum itself but all things being
equal which they're not. Same airflow into each cylinder so you're equalizing your air fuel ratio
across each cylinder. Any truth in that or am I getting on the wrong track?
No you're bang on that's 100% but the drama is it's outside the RPM window that we need
and it's same when you come down to manifold so if you look at it like a hypertune versus
plasma man so I've worked with plasma man Alex and give him a little feedback same as Jay from
Real Street he's helped him over the years but he's shrunk his cross-sectional error at the window
now gone to an oval and a lot of the 2J staff and gone to a smaller radius and that manifold
you know at 8, 8,500 will make more horsepower than a hypertune but then at 10,000 RPM the
hypertune will make more horsepower because now it's coming into that velocity zone that inertia
this is why we map the cross-sectional area and see what velocity dynamically it's going to have
on a running engine and like we said about the minimal cross-sectional area getting it to that
600 feet per second is the key so I've seen Seedhead if I just do the math on an 8,000 RPM
RB26 we're about 550 feet per second so we're not even in the range yet where my hand-ported
one's about 290 so I'm already 40 feet per second up on the Seedhead and that's the problem and I'm
still short this is why I weld up the divider and try and prove it that the RB is actually too big
for that engine that's why they really come alive on the 2.3's and 2.2's and 3.4's that's
where they come in their own you know. Yeah okay the bigger engine can actually use more of the
flow. 100% and that's where they really start to come alive you know. Okay all right I'm gonna
guess I know the answer to this question but are you leveraging any technology such as 3D scanning
and CFD to help develop the ports or is it purely sort of old-school tested on the flow bench and
the dyno I guess ultimately? Yeah I have but I find with CFD CFD's much like a flow bench it cannot
tell you how good the cylinder head is or if it's the right size so it's going to give you a great
velocity gradient and show you you know airspeed through the port and stuff like that but at the
moment it's still it's probably it'll get you 95% there but the drama as you know at the end of the
at the race end we're playing with 1's and 2's not not 5's right so it's about collecting as many
1% as you can like you said valve seat angles and stuff like the port velocity. I guess as if it's
a valid tool to a point though it could do a lot of good to get you close to the ballpark without
having to spend hours hanging on a die grinder physically porting a head and then testing it.
100% and it's really good for those guys that don't quite understand engines properly because it'll
get you in the ballpark to a certain extent as long as you know what right data to put in and
depending on what system you're running whether it's a RANS because RANS is very basic it makes a
lot of assumptions but I get a ton of people sending me because I help design manifolds for
industry like production manifolds and stuff like that so I get them sending me a lot of CFD
and then I'll analyze the cross-sectional area and the engine and what they're actually doing for
it and see if they're even in the ballpark you know and they might look great on the CFD but
the sizings are wrong the plan of my openings too big the radius is too big or you know what I mean.
So just a yet another example of garbage and garbage out.
Yeah 100% like any it's only as good as what you put into it and you've got to use other things
like OEM manufacturers won't just use CFD they're using Riccardo wave they're using a ton of other
things and their CFD is you know half a million dollars not like the stuff we would get off you
know CAD but so they're not only doing what we call steady state they'll actually do a firing order
and then use like D1 Riccardo wave to estimate the harmonics as well so they're balancing both aspects
of that and then adjusting the CFD and then looking at the sound aspects of the manifold
and getting it right from them but again a lot of OEM are driven for emissions and there's other
aspects there too. Yeah different priorities to us in the aftermarket of course of course.
Yeah that's right. Okay yes this is probably an easy segue into the next topic which is the design
of intake manifolds and I think there's as much confusion around this as there is in cylinder
head porting as well so I guess there's a lot of area to cover here. One of the first questions
I'd have is what do people typically get wrong or misunderstand about an intake manifold or
plenum design? Generally run a length and its size and you know tapers, angles, all this sort of
stuff I think the biggest confusion is around that. I get some funny questions, I've had some
funny questions over the years even people's understanding as far as length goes as far as
torque versus so short runner versus long runner but my first question is well what's short and
what's long? Yeah you've got to get a little bit more granular moment. That's right so some people
might call a 12 inch along runner and a 6 inch short runner but at what RPM and what harmonic
are we targeting the fourth harmonic, the third harmonic and generally all race engines around
the world unless it's an emission engine or a restricted class so just talk open you know
trying to make as much horsepower as we can are targeting the third harmonic. That's the best balance
between velocity and our harmonic sound element type deal which is worth about 5% to 7% more
That's no joke. No, no. Can you just briefly explain the sort of mechanism behind this third
harmonic and how it actually aids cylinder fill? Yeah well we've got two, we've got a quarter wave
and we've got a third harmonic. The third harmonic is when the valve is open so what we're trying to
do is time the valve when it closes so basically when the valve opens we create a depression,
a negative pressure so we have a negative wave that runs up the runner at the speed of sound.
Also what we've got to realize is it's location dependent meaning if it's in velocity and we
have this same problem in exhaust when some people try and calculate wave signals for exhaust
what they don't realize is if the medium is moving at a thousand feet per second and the
speed of sound is 2,000 now it's only moving at 1,000 relative to pipe length right? Does that
make sense? Yes, yeah. So we have the same problem on the intake in a way that we need to compensate
but we generally just use averages and they work at about 1,085 at 25 degrees. So when the
valve opens we get a negative pressure wave that runs up to the plenum runner right? To the opening
of the plenum. The instant it hits that plenum runner it will flip polarity and come back as a
positive wave right? The negative wave goes into the plenum but we get a polarity shift and that
wave comes back down. Now it'll go it'll hit the valve seat and it'll flip polarity again and then
go back up and down. So what we're trying to do is time that positive wave to come back in
right as the intake valve is closing. So this is a more dense zone of air so think of boost when
when we see boost we're pushing the molecules of air together that's how sound works. If you've
ever seen a sound wave the the wave action we have positive and negative pressure right?
So we'll get this positive vein of air that's more dense and if we can get that into the cylinder
just as the valve shuts now we've got better cylinder filling and again like I said that's
worth about five to seven percent more horsepower if we get that timed right and that's what all
your pro stock and top NA stuff is doing and then we have our quarter wave which is when the valve
shuts we have a wave that a positive wave that'll go up invert negative come back down negative go
back up come back positive and then if we can time that one right as the valve opens we end up with
a positive shift especially on valve overlap because this is where we have no piston speed
that there's nothing to generate a pressure offset so what we're relying on is the negative pressure
arriving as the exhaust valve opens and this positive wave to help create that exchange and get
better overlap to flush the cylinder out right because if we don't want that
get gas in there because that costs us horsepower. Of course yeah it is quite a obscure
sort of concept to get your head around and again we're not helping ourselves here without the
benefit of some animations but we're doing the best we can here so hopefully people are
sort of still sticking around and understand this. The problem with that is what works at
let's say 3000, 4000 RPM, the length that works to capture that third harmonic is not going to be
the same at 8000 RPM and this is where we get into that. Long runner is going to be beneficial
for low RPM torque and a short runner is going to be beneficial for high RPM torque and hence
horsepower. So I guess anything and everything in engine design and development is a compromise.
How do you decide on the compromise that's going to be suitable for a given engine
application and hence the design of the intake manifold? Well if it's all out drag racing most
of those engines are only working in a 1500 RPM window so from peak torque to peak horsepower
15, 1800 max so we will target peak RPM for a harmonic thing and like on super stocks and stuff
like that we're talking at about 10 and a half inches and that's total induction length so you
can end up with you know five inch runner on top of that where if you're talking endurance or street
you generally want an inch or an inch and a half longer so the wave comes in earlier because
like you know in a circuit car we want 33 and a half maybe even 4000 RPM range
and sometimes we're short shifting we're not using that you know let's say our red line is 8500.
We don't use the red line like a drag car wheel like a drag car needs to over rev
as well because we don't want to end up under our peak torque point so depending on the gear ratio
if let's say the limits you know 10-5 we might go in first gear 10-7 so that when we shift we don't
end up in a low torque position you know what I mean we're in a circuit car that's not as bad so
what we try and do you're looking at average numbers so you'll even target different velocities at the
entry of the port so in a in a pro stock thing in a true earth third harmonic we might only be 180
feet per second coming into the runner where in a circuit car it might be 195-200 right because we
want better we don't care if we lost 10 horsepower if we made 50 horsepower at 5000 and lost 10 at
7 it don't matter because that's what we're going to use that's the that's the area under the curve
that's more important that's right 100 yeah so in that aspect you can play with the induction
length and the cross sectional area because that's the other aspect that a lot of people don't get
I can make a short runner act like a long runner just by closing the cross sectional area up and
getting that average velocity up and that's what we do in you know street tunnel rams where we can't
put a 14 inch runner in it we can only put a six inch runner in it so we'll close that CSA up holding
are a great example of this you know yeah okay in terms of theory versus reality I'm just wondering
how well the calculations validate once you hit the dyno like are they spot on or do you have to
kind of go plus or minus let's say you know half an inch and see where where it actually truly works
out um no they're pretty good now after sort of people have been playing with this probably since
1950 since carizawa first started testing uh induction length you know they had the you know
rubber tube rubber with the tubes and they just move it up and down that was just on a parallel
tube obviously a runner needs to be tapered and that changes the aspect a little bit but with
programs like pipe max and I've got all my own ones now I've also built a calculator platform
called Einstein motors where I have them all on there but they're within probably a hundred thou
now so if you if you're chasing chasing horsepower you're probably talking a calculator to real world
is within about a hundred thousandths in length okay all right yeah they're pretty much done to
death in in like motorsport I mean it's it's great when the theory works out in reality but
you know my experience is that's not always the case yeah yeah now with as long as you know
the temperature of the air because the physics doesn't change you know and that's the brilliant
thing about harmonic theory and and calculating it if you know the density and we
know we have our calculation or a temperature sorry not density density won't affect the speed of
sound but if if you know the and this is where even in boosted application we still tune third
harmonic and you'll see better horsepower per psi and so on you know but um yeah no it is
very very close and same with the minimal cross sectional area and we actually did a video on
YouTube for one of the big block manifolds that we were building and I showed all the math and
how we built it even before the engine was dynoed and it was on a sunset 632 big block
and in the states they make about 40 horsepower from single plane to their tunnel ramp but they
go to a fourth harmonic because they can't make the third harmonic and I have a different theory on
that I tend to put more port energy in them so I was actually 20 mil short on the third harmonic
but I still made it long because I wanted more average velocity and we end up making 72 horsepower
more they make 40 and the car actually went on to win drag week top NA so Australia's fastest NA
radial car that's impressive yeah we showed the math no flow bench no nothing all on the whiteboard
and then built the manifold no flow bench testing no nothing that's the other aspect a lot of people
go down the road or the rabbit hole flow testing manifolds that can't tell you anything
you can get data off a cylinder head but flow testing and manifold really won't tell you much
at all especially with a manifold that has uneven runner lengths because you have to target different
velocity factors in different cross sectional areas so if you actually get them right on the
flow bench they're wrong on the dyno or wrong in the real world oh well yeah yeah so that could
really send you in the wrong direction with your development.
Yeah definitely and you see that with more so single planes but we don't flow test any of our
time arams are all done by math and they all within 1% of our calculations every time yeah.
Okay in terms of what next aspect I want to talk about with the plenum design is the actual
plenum volume so is there any rule of thumb on what this should be compared to maybe
inch capacity and how does varying it up and down affect engine performance?
There's a couple of rules but it really comes down to what I call how much bias does the throttle
body supply so in other words if we've got a forward facing manifold that probably has the
worst bias of all right versus say a tunnel ram so tunnel ram needs the lowest amount of
plenum volume so let's let's let's just take the target of say seven to seven and a half thousand
right the most of your common plenums in your turbo cars that with a bias plenum they're going to
start at around about a hundred percent 10000 and twenty percent generally right that
seems a really really good compromise because what I look at is exchange rates so every 720 degrees
at 100% will exchange 100% of that plenum volume so now we're looking at how fast the velocity is
in the plenum and how much it's going to rob the cylinders so there's a there's a slide rule
that generally states as we increase rpm we want more plenum volume because we've got to reduce
velocity to stop cylinder robbing and we see this with small plenums right as we start to rpm
if you've got egt's or anything like that you'll you'll see the separation starts to broaden much
quicker we might only have you know three or four percent at 7000 we get to 88 and
a half now we have 10 12 percent right yeah okay there's a slide rule but when when you look at
say a tunnel ram we start looking at line of sight the between runner and throttle body
they're all exactly the same so now we're able to reduce that plenum volume and increase the
secondary harmonics in the plenum so when we're talking about wave harmonics and that positive
wave coming up the runner and inverting and going down the runner well that positive wave
goes into the plenum and we can harness that positive wave to help fill other cylinders this
is why common v8 plenums will have a far more smoother curve than say itb itb you'll see the
rarefication points in the curve the dips right yeah that's because we have no cylinder to cylinder
positive swapping of that secondary harmonic where a common plenum like a tunnel ram we do right
or even your six cylinder stuff anything with a common plenum we can help fill that rarefication
wave that's coming out of another runner with a positive wave so there's that aspect and then
with carburetted we want to keep the plenum volume low enough that we're getting good
booster signal because as we start to move the carbure way we start to lose signal from that
runner right and we have a few aspects going on there so you're obviously familiar with shear
plates right yeah yeah or actually let's explain that for people who haven't heard that same though
yeah so a shear plate is basically a plate that goes under a carbure that'll have a really really
sharp edge and have voids under the side of it right and it has two functions and you really
you really need to use these on big camshaft single plane manifolds that don't have a lot of
plenum volume and you're starting to get fuel distribution problems and what that generally
is is that positive wave we talked about that comes up the runner comes up and washes the
booster signal out so remember that's a negative pressure we're trying to create in there to
pull fuel so as this positive wave comes up into the booster it stops fuel flow so you're gonna go
linked yeah exactly so what the shear plate does is one it allows the fuel to shear off being a
shear plate so it allows it to fall and go into the runner but the second aspect is it'll create two
negative zones or it'll create negative zones under the carburetor so these eddies of negative
pressure right lower than atmospheric so what actually happens is as the positive wave comes
up the runner into the plenum it'll get attracted to the low pressure because a high pressure always
fills the low pressure so rather than going up into the booster it gets dampened out by those
negative pressures under the carbine yeah that makes sense yeah so then in that aspect with the
carburetor we're able to reduce that plenum volume so that's seven to 8000 rpm figure we're
going to start at like 55 maybe 60 percent plenum volume but as I was saying we put the throttle
body at the front now we've got more more biases in the plenum right the throttle body has to work
harder to supply air to all cylinders we have more turbulence to deal with because now we're
trying to get say air from the throttle body to number six at the back overall these little
explosions because that's the other thing people don't understand up until peak torque your engine's
spilling back into the plenum you've got reversion coming up and these little explosions going off
in your plenum right I think John Kasi showed this best when he put his finger in the manifold I don't
know whether you've seen that video I have not oh it's a great video so look it up online John
we'll see if we can find that and chuck it in the show notes as well oh also for my own personal
enjoyment yeah basically he's put his finger in the runner and nearly snapped his finger off
because the the wave harmonics going up and down so yeah I think when you start diving into this
you sort of realise all of the assumptions that you've made maybe maybe are completely out of
order and also just honestly these things are much more complicated than you give credit to
when you're just looking at it from a cursory perspective 100 percent I'm interested just
because you mentioned ITBs, I guess at least on four cylinder stuff maybe more so than V
configuration stuff the ITB is on a naturally aspirated engine is often kind of seen as the
Holy Grail that's the epitome of performance. Pros and cons versus a plenum in a single throttle
or double throttle body? Yeah we get a bit, I've been doing a little bit with Dave from Skunk 2
Racing they're one of the fastest pro stock Hondas in the world they're 10,000 11,000 RPM I
think they're doing now ITB and they run the Kinsler yeah I don't know I think ITBs are brilliant
for torque on demand because if we need less cross-sectional area we just give it less
throttle and it creates more turbulence and it eats up that cross-sectional area so that's why
they've been brilliant for circuit cars but I think all out power we've done a couple back to
backs on V8s for like LS7s and stuff like that and middle we've gone to a shorter runner but
from like the GenV stuff which is a reasonably good ITB setup because the ITB the general rule
is the further we get the throttle body away the better because all ITBs will create a trailing
weight generally five to six inches at 300 feet per second and those little eddies and there's an
actual physics term I can't remember what it's called but every inch it travels the eddy will
halve its size so if the eddy was you know half an inch it'll be a quarter by an inch and so on so
you get a degradation phase after that so that that tends to eat up a little bit of cross-sectional
area so this is obviously why Formula 1 went to barrel valve I think that's the optimal because
then we can actually you've got 00 sort of turbulence when it's wide open throttle that's
right because the other aspect you'll see this in Europe some some of them get right into instead
of having a shaft and a butterfly they'll see and see the whole plate and screw into the end of it so
it's all one piece so it's smooth and they've done CFD and it's you know like 12% reduction in
turbulence all that sort of stuff make a little bit more horsepower but yeah we did a back-to-back
I think we made an extra 120 horsepower with a common planum interesting yeah so but I'd like to
do some more more testing on that. I think a colleague of mine used to used to work for me
he's actually been on the podcast Chris who now runs his own tuning shop prestige tuning in Wellington
and he was doing some work on a V8 touring car with an LS7 and they put the Harrop ITB set up on
which is cringingly expensive and he tuned it and it wasn't really a step forward and I think
they ended up making more power everywhere using the MSD Air Force intake manifold over the Harrop
which is also substantially cheaper so sometimes ITBs aren't the be all and end all.
Yeah my theory is that you should be able to make 3 to 5% more with a perfect common planum design
over ITB and I've sort of seen this a little bit when we've done tests with ITB building
planum boxes over the ITB we tend to smooth the horsepower curve out and even if we haven't made
any more peak our average seems to be better because we've got to smooth the curve and I've had a
few guys in Europe that I help they've played around with carbon fiber air boxes and bits and
pieces and they're claiming around about 3 to 5% better horsepower so yeah I don't know.
I think the other part of this that is worth mentioning is while clearly tuning on ITBs is
not complex, I think it's fair to say that tuning a common planum just off map is probably still
easier in general than tuning an ITB engine, so that's something you can't completely ignore.
Another one that sort of feeds into this I think, a pun not intended but is the throttle body
and there's again a huge amount of debate and sort of misinformation around throttle body sizing.
I think in my experience most people probably oversize the throttle body. What do we need
to know about this and what are the downsides if we go too big or too small, too small I guess
is we make less power but yeah give us what we need to know. Yeah I think that like you said
especially in the turbo game a lot of guys you know you see you know the RB is a perfect example
100 mil throttle bodies and stuff like that where an 85 or even a 76, 75 would do the job
depending on horsepower and RPM. I generally target them to about 150 feet per second of
engine mass volume what they're using so that way it's a sliding scale to RPM. The more RPM you
got the more CFM you're going to use the higher the sb becomes at the throttle body so circuit
stuff I'll target about 200 feet per second and the like all out horsepower stuff at about 150
feet per second and that's roughly what even the new pro stock target says that so they're oval
holly throttle body at 25 square inches that 1500 odd horsepower works out about 150 feet per second
through the throttle body like what you're saying smaller throttle body costs your horsepower because
the sb becomes too fast then the throttle body starts to become the choke too much turbulence
but at 150 feet per second it's very very minimal you could you could possibly push that to 125 if
you're trying to make you know that last 1% on the dyno but the 150 feet per second target seems to
be the best approach from what I've tested and like you said what you're going to lose generally
it's hard to hurt even torque with a bigger throttle body but what you lose is that throttle
sensitivity right so the driving ability now all your engine is in the first 15% not you know.
Yeah I think that's something that's very easy to completely miss is the drivability that a big
throttle body loses and the inability to accurately modulate the torque output of the engine and
particularly if you've got a powerful engine that could be really problematic. Granted I mean drive
by wire throttles with the way we can map pedal position versus throttle position you know we
can work around a bit of this but I mean ultimately if you're in that situation the answer is you've
got a throttle body that's bigger than you need. I like your analytical approach here, I think
I guess probably 99.9% of people are choosing a throttle body based on you know how they feel
on the day with what the weather's doing or what their buddy's put on his car last week
as opposed to having a line in the sand, this is the airspeed we're looking for, now we can
calculate what size throttle body actually fits that application. That's right and it's the same
thing with air cleaners, it's the same thing where everything, that's why I built all my calculators
even on air cleaner size right so you can calculate the surface area and the required
feet per second that you need but before it becomes a velocity restriction you see that
even in turbo cars most of them have a pod that's too small and now you're starting to see it even
in some of the big Mustangs, now that they're needing to make 800-900 horsepower they're even
putting twin air boxes on some of the like dark horse and stuff like that now because they need
so much surface area otherwise the velocity through the air cleaner is just going chocking the engine
you know. Yeah right fair point, just coming back to the ITB thing and this might be a moot point
in light of what you've said about runner length, I think one of the perceived advantages is that
it's very easy to change your trumpet length to affect your overall intake length and hints
on the dyno, play around with some different trumpets and tune the power and torque curves to
get them exactly where you need but again as per our conversation maybe we can just calculate that
and be done in one go so irrelevant. Yeah and we've seen this transition even with like super
car hyper cars and everything you know Ferrari was very much ITB Lamborghini so now they're all
gone to that common platinum type design you know parallel roof they're trying to harness that
secondary harmonics they have smoother horsepower curves now but I think the best advantage and
why you still see it in super bikes and all that is because they're talk on demand you know that
they're not at full throttle all the time you know even the best riders I think they average
62% you know at full throttle around the whole track so and you'd know this drive in an ITB car
the worst thing you can do is just go flat to the floor at two grand if you squeeze the throttle
you'll make more torque right you'll come out of the corner faster right in a circuit car if you're
giving it 50% throttle versus full throttle that's a 3500 out of the corner if you just back that
throttle off more the car will actually pull out of the corner quicker you'll see your torque go up
right and that's that talk on demand because we're creating more turbulence which right which
basically dynamically shrinks the the port for you. So somewhat counterintuitive really.
Yeah it is a little bit yeah. Okay all right let's move on we're getting a little bit long
here I just wanted to sort of finish off I guess with asking you if there's a particular engine
or project that sits in your mind is something you're sort of most proud of or something you
learn the most or maybe something that just completely disintegrated on the dyno and you
first twin turbo is pushing a factory block that was it's over probably well over 20 years ago now
and that that taught me a lot of lessons touchwood it never broke but yeah we end up pushing a
factory 010 block to 1200 horsepower yeah I still I still get people today calling the BS
yeah that that was my what what do you think it was about that particular engine that that held
together. RPM I think yeah RPM so we limited RPM to basically 7000 RPM so we made like I broke
all the rules I put small ARs on it admittedly I did use tune length runners like exhaust manifolds
on it we had a tunnel ram on it we had a fair bit of plant and volume we had an ice cooler
which we actually made out of three Nissan 33 coolers you know the ones that go at the factory
ones that go under the guard so we cut the tanks off them I welded three together and made a tapered
planum and put it inside an ice box and even that I think we've seen like 19 degrees inlet
air temps even I think well 10-12 dyno pulls in we're still only at 21 so well yeah that was a
that was really a lesson for me and it really opened my eyes to how easy turbo cars were
making horse power you know man. Well here's one thing I'll say about that and yes they are
obviously but when it comes to trying to keep a factory block together they can also be your
worst enemy because they'll make so much so much low end torque and I think it's until you realize
that it's actually cylinder pressure and hence torque that we need to manage and it's very easy
to wind the turbo boost up and break the engine because you're making too much cylinder pressure
whereas if you're actually a little bit smart about that and the flip side of that is what you
mentioned there, keeping the RPM under control because in my opinion the two killers of an engine
will be cylinder pressure or torque and RPM so you want to manage both of those but a really
powerful trick to keep an engine together, making a lot of power where it's got some
weak points maybe the connecting rods is hold the boost low until your past peak torque and then
you can ramp that boost in as the RPM increases so you're actually sort of getting a flatter
torque curve and you're managing that cylinder pressure but of course torque modified by RPM
divided by 5,252 is out power so more torque at higher RPM, happy days. Yeah we've seen that with
the 2Js, the stock bottom end will help a lot of guys back in the early days and I think even
old Rocco and a few of them were running like 7 seconds with fact like jump yard engines you know
and then the precision turbos come out and they were bending rods left right and center because
they were coming on about 600, 700 RPM earlier right at that you know 3500 RPM on a stock 2J
rod and they were just going bending up but yeah you're 100% wrong. I mean the other little
tuning trick we can use there as opposed to or as well as boosts of course is to back off the
timing through that peak torque. Yeah there's pros and cons with each technique but those are
kind of the two main levers that we have available to pull. Yeah definitely. Alright Jake it's been
an amazing chat. Actually before we get onto closing this off just one thing I wanted to
mention that's become very apparent as we've gone through this discussion is that you're
incredibly smart when it comes to all of these aspects and I'm wondering how much of this you
picked up in study before you started your career versus how much you've kind of picked up and
learned and studied along the way since you've been building engines or is it both? Yeah everything
was study originally so basically and like I worked with a few guys along the way and I found
that they would just test stuff blindly and it might have took them 10-12 goes to find the right
combo. So I started off really early in studying engineering and studying all the things so I went
out to prove my theories and I found that I could get it right within two or three goes. So I found
I didn't need to do as much testing and I could get the results faster because I had a better
understanding of those engine fundamental principles you know what I mean? Yeah that makes
perfect sense. So yeah that tended to help me a lot and the other aspect was we never specialized
in one engine. I did an array of engines, twin cams, you know two valves, small block shaft
fords and you know RBs and SRs and it helps you see the common denominators between all
the engines and that's air speed cross-sectional area and that really helped me bring it all
together to go well it's all physics. If we understand the physics then we can apply that to
any engine and it works you know. Obviously we just need to understand what are the like you said
the weak points of a particular engine you know SR20 or a rod in this engine or a block in that
engine you know like the 1UZ I think the block the limitations is about that 1400-1500 horsepower
that we're finding now you know. Yeah I like when you noted when you mentioned the SR20 you just
left that as the overall overarching problem with that particular engine. Yeah maybe I agree,
hasn't been a good engine to me at least anyway. I think what you're saying there as well is sort
of almost mirrors my attitude to tuning different engines. I think a lot of people will believe
that if you haven't tuned you know 102JZs, well you can't come fresh in and get good results out
of a 2JZ or sub in your particular engine of choice. The reality is and you kind of alluded
to this maybe not being entirely right but I do call the engine an air pump which essentially
it is and if you understand the operating principles of an engine, you understand how fuel
injection works and the principles of tuning, I can apply that broadly, completely blind to an
engine on a dyno I can't even see and I'll go through and tune the engine, I'm going to get
good results out of it. There is no magic here I don't believe. 100% and our understanding nearly
every engine wants that timing to land at that 10 to 14 degrees after TDC. That's where we want
our peak cylinder pressure and like you said early or late is only going to hinder us right,
we hit it too early, we're going to get pre ignition detonation and so on but yeah
once you've got the fundamentals then you know what air fuels work with what fuels
you know what type of fuels you're using, yeah it's pretty like like you said in all the engines
I've tested the air fuel, the same fuel with different engine combos might only change by
0.2 of an air fuel you know. Yeah there's a few, I've sort of seen this in a couple of podcasts
recently so I won't really go over the same story again and again but I mean I do think a lot of
engineers will go into every engine tuning project with a lockdown like this is the air fuel ratio
I'm going to run and you'll be able to get results, don't get me wrong, engines don't vary
that much but I do suggest that a little bit of experimentation particularly on an engine that
you've found is knock limited, you're not at MBT and you can't get any more timing into it,
oh sure let's see, does a richer air fuel ratio cool the combustion charge enough that I can
now creep in 2, 3 degrees more timing and net gain in power and torque, that's just sensible
I believe. And understanding that the air fuel itself has an acceleration factor, right?
So different air fuel ratios have different flame front speeds so they'll actually change
our delivery timing you know. Yeah correct, yeah. Cause you hear a lot of people they'll
chase an air fuel and then put timing in but if they just adjusted the air fuel they can put more
timing in and there's a little dance there you know and then. It is definitely a bit of a dance
yeah, yeah for sure. Yeah 100% right. Alright we'll move on to wrapping this thing up and as
always we've got the same three questions, we ask everyone the first of those questions is
what's next in the future for you? Next is we're building just my calculator platform
Einstein Motors and we're going to build a hopefully another factory out at Bathurst back to
where Bain Racing all started four generations ago with my grandfather because he designed
Mount Panorama was because him and my grandfather were drinking buddies so and he used to race down
the old Vale dirt road that's when they had when they used to race so he talked them into building
a racetrack and that that become Mount Panorama so we're going back back there
and we're probably going to go into a few more street cars because I have my son coming up into
the business now so he does some of my engine program now and some of our manifold welding and
fuel tanks and stuff but what I want to do is take him back to grassroots and get him tuning
some street cars because I think the best engine builders are also tuners they tell a story you
know if you can lean an engine out then pull it down have a look at the valve seat have a look at
the exhaust valve see what it's doing to the seat see what it's doing to the rings and understand
all vice versa run it too rich and watch how your rings tear up and stuff like that and just
help him understand both sides of the fence I think it'll make him a better engine builder and
a better tuner you know yeah I think you yeah that's a really good point that maybe I haven't really
highlighted for myself as well you know when I was deep in the 4G63 drag racing world and
we had a lot of success with my own car so of course we ended up with a lot of customers
running 4G63s for drag racing and there was a handful maybe three or four engines that I did
that were methanol sort of 12 to 1500 horsepower capable and it was quite nice being able to
build the combinations which were essentially all identical send them out do a season of drag racing
get them back and get to tear them down and you can start iterating on things like piston
to cylinder wall clearance maybe the bearing clearances maybe the ring end gap and kind of
see how that actually panned out over a season of drag racing and that kind of accelerates your
learning I think off the back of customers but they're still getting great results so everyone's
happy. That's right yeah they all tell a story and you can definitely learn a lot from just looking
at even the burn pattern on the piston like we do that with we'll run an engine on the dyno and
just pull the intake manifold off and look at the intake port and see where the injector is if it is
wetting down anywhere in the intake port you know just to give us an idea of what the injector like
even that conical angle we've played with that you know and trying to get it midstream not shoot at
the valve like a lot of people think the best position for an injector is at the back of the
valve but even the Yamaha testing has shown you'll actually make less horsepower or if you move the
injector back a little bit and shoot at midstream so that you know 30 37 degrees to floor but midstream
so it catches it and time it properly in the ECU you'll actually make more more horsepower because
your SMD that solder mean diameter of the fuel molecule actually ends up smaller going into
the combustion chamber and that's what we're trying to get the best homogenised mix you know.
I think I fell into this trap as well, playing around with injection timing and thinking that the
perfect timing would clearly be to inject on an open valve and then you sort of realise that actually
that's not the case because even what looks like a finely atomised mist of fuel coming out of a
good quality injector, the size of the fuel mist, liquid fuel essentially what I'm trying to say
doesn't burn very well, what we actually want to do is inject against the port wall and the hot
valve and then it's going to evaporate, go through that phase, change from liquid to gas
and then we're inhaling a gaseous form of fuel which is much much easier to ignite.
Yeah that's right, even when we did dyno tests we moved the injector up and the runner
and you know even three inches we made I think 14 or 18 horsepower and just a baby 450 horsepower
engine you know because we've got more time and like you said another quick fallacy is that
carburetors don't atomise fuel as well, they're salt and mean diameters nearly 10 times smaller
than an average injector so yeah yeah it's pretty interesting.
Yeah I don't want to get too deep into this debate, there's always been sort of an argument
mainly from the fuel injector crowd that fuel injection is going to make more power than a
carburetor and I think I believe that for the longest time and then once you sort of start
digging into it, you know I mean all things being equal which clearly they never are,
that actually maybe is not the case and a carburetor still can do a very good job,
the carburetor does a very good job under specific conditions and as soon as those conditions change
all bets are off. That's right, yeah 100%. Yeah carburetor generally is about 2% more horsepower.
Right, that's probably a podcast for a different time. Definitely, you've probably touched on this
earlier but I don't know if there's anything more you want to follow up with or anything else
you want to add, is there any advice you give to a younger version of yourself to help reach
where you are today in your career faster? Yeah just read as much as you possibly can and understand
what you're seeing. A lot of times we'll do something and make horsepower and not understand
why and I fell into this trap years ago with planum volume on the dyno. With a tunnel aim you
can put more and more planum volume in an engine and make more and more horsepower on a dyno but
go slower at the race track and that comes back to that signal. So try and understand what you're
doing and try and only change one thing at a time. Don't change, especially if you're doing
like testing and you want to validate your ideas and theories, only change one thing at a time
because if you change two or three things you don't know what made the horsepower, you know,
you don't know. That was actually a problem I often found myself in with my own drag car
and we had a budget that was essentially non-existent and you had a limited amount of time
and ultimately I needed to be spending my days working on customer cars to fund this drag racing
addiction anyway so you could never just make the one change. It was the compression ratio
and it was the injectors and it was the planum and it was the turbo size and cool we made another
100 horsepower or which of those changes, and maybe if we hadn't made one of those changes
it would have been 120 horsepower or 150 but difficult, you can only do what you can do I think.
Yeah I see a ton of that in the industry, they'll do three or four things and then they've lost 50
horsepower and they're scratching their head, which one was it? Yeah yeah it's a tricky situation.
All right our last question for today, Jacob, people want to follow you and see what you're up to
and I mean I highly recommend they do, we've scratched the surface here but in researching
this podcast, your YouTube channel and by definition there, your Instagram as well is an
absolute goldmine of information for those who want to dive way deeper than we have today.
So yeah how did they find you? Yeah pretty much YouTube main racing, yeah that's probably the
easiest approach and Facebook we put a little bit of stuff up on there but yeah the YouTube's
where it's at if you're interested in engine science and airflow and everything engines here.
Okay perfect as usual those links will all be in the show notes. Luke Jack has been great to
dive into this, I was probably through a lot of this right at the very limit of my own knowledge
and I don't profess to be a cylinder head porter as I mentioned, quite happy to leave that to those
who know what they're doing but yeah they've filled in a few blanks for me and hopefully also
for those listening so thanks for your time. Awesome, not a problem.
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About this episode
Airflow and performance aren’t just about bigger ports or higher CFM—hosts and guest dig into flow rate vs velocity, boundary layers, and why flow bench numbers can mislead. The discussion connects intake runner length, plenum volume, and pressure-wave harmonics to where torque and horsepower show up across RPM. They also broaden into reliability: harmonic dampers, bearing clearance, heat saturation, and how tuning choices affect cylinder pressure, detonation risk, and component life.
Some people learn engines by doing—others take it a step further and truly understand the physics behind what’s happening. Jake from Bain Racing sits firmly in that second category, combining hands-on experience with deep engineering knowledge to build some seriously impressive engines.
In this episode of Tuned In, we dive into Jake’s background and how a family history steeped in motorsport set the foundation for his career. From building cars in his teens to running his own shop and developing race engines, Jake shares how a mix of curiosity, study, and real-world experience shaped his approach to engine building.
We cover the fundamentals that underpin everything Jake does—covering topics like harmonic dampening, bearing clearances, oil viscosity, and why many common engine-building “rules” aren’t as black and white as they seem.
Jake then unpacks airflow and cylinder head development, breaking down the often misunderstood relationship between flow and velocity and how factors like surface finish, valve seat design, and port shape all contribute to real-world performance. We also explore intake manifold design and the role of runner length, plenum volume, and harmonic tuning in maximising engine efficiency.
This episode is packed with practical knowledge and deep technical insight. Whether you’re building engines, tuning them, or just want to better understand how they really work, Jake’s ability to connect theory with real-world results makes this one a must-listen.
0:00 Intro 4:16 How did you get interested in cars? 10:45 If an engine is balanced why do we have harmonics? 18:05 How do you learn to build performance engines? 21:48 Compression ratios for different applications 26:53 How did you build up your knowledge? 30:54 At what point did your current business take off? 33:15 Bearing clearance vs oil viscosity 41:13 What’s your opinion of billet blocks for street engines? 44:43 Is it hard to make a profitable engine building business? 48:50 When it comes to cylinder head porting why is big not always better? 51:52 Why is velocity so important? 57:20 What is the optimum surface finish for a port? 1:04:04 What’s the best approach to use when porting around the guide? 1:08:00 How important is the valve seat? 1:10:45 Are your heads all CNC ported? 1:15:58 How are you testing your heads and porting? 1:18:42 What do most people get wrong with intake design? 1:20:10 Can you explain the 3rd harmonic and why it’s important? 1:23:45 How do you choose the design of the intake manifold for a given engine? 1:26:00 How well does your calculation validate on the dyno? 1:29:22 Is there any rule on intake manifold volume? 1:32:16 What is a shear plate? 1:34:51 ITB’s vs single or double throttle body 1:38:43 How do we size our throttle body? 1:43:49 What’s been the most interesting project? 1:52:17 Final 3 Questions
