Why MORE Horsepower Is LOSING In 72 Fast Diesel Racing

In the Fast 72 diesel racing rules, competitors are limited to a turbocharger with a 72 mm size. That size constraint heavily limits how much airflow the engine can move, so teams focus on making the engine efficient and matching it to the turbo’s operating range.

A turbocharger uses exhaust gas to spin a turbine that compresses intake air before it enters the engine. In diesel racing, turbocharger sizing and calibration are central because more (or better-timed) airflow usually means more fuel can be burned efficiently for power.

ECM stands for Engine Control Module, the computer that controls fueling, boost targets, and other engine parameters. “Factory ECM” implies competitors must use the stock control hardware/software rather than swapping in a fully custom ECU, which limits how much they can optimize the engine.

An air-to-air intercooler cools the compressed intake charge using ambient air flowing through a heat exchanger. Cooler intake air is denser, which helps the engine make more power and reduces the risk of heat-related issues under boost.

A water-to-air intercooler uses a liquid (water) loop to carry heat away from the intake charge and then rejects that heat to the air. The host mentions it because the rules disallow it, since liquid cooling can enable more aggressive temperature control (including “ice box” style setups).

Nitrous (nitrous oxide) is an additive that can increase oxygen availability and combustion potential, often used to boost power. The rules explicitly ban it, meaning competitors must make power through the turbo/diesel/fueling setup rather than chemical injection.

Water-methanol injection is a system that sprays a mixture of water and methanol into the intake to reduce charge temperatures and can improve knock resistance. The host lists it as disallowed because it would be a “trick” way to increase effective power beyond the allowed hardware and fuel-only constraint.

The idea is that the highest single-number horsepower on a dyno doesn’t automatically translate to race wins. Race outcomes depend on how effectively the engine makes power across the RPM range you actually use, plus how reliably it holds that output under track conditions.

A chassis dyno measures a car or truck’s output while the vehicle is strapped down and the wheels spin on rollers. It’s used to generate power/torque curves and compare setups like turbo size, fueling, and engine internals under controlled conditions.

A dyno appearance is when a vehicle owner or builder brings a truck to a dyno facility for public testing or demonstrations. In racing communities, these runs often become reference points for comparing builds and validating claims about power.

Cylinder heads are the top castings of an engine that house the combustion chambers, valves, and ports. In diesel performance builds, cylinder head work (flowing ports, valve sizing, and combustion-chamber shaping) can strongly affect how much air and fuel the engine can use efficiently.

Camshafts control valve timing and lift, which determines when and how long the engine’s intake and exhaust valves open. In high-power diesel builds, camshaft choice is a major lever for matching airflow and fueling to the turbo and the engine’s intended rpm range.

A stock cam is the factory-designed camshaft profile, meaning its valve timing and lift characteristics are tuned for broad drivability and emissions/efficiency rather than maximum peak power. In diesel racing discussions, “stock cam” usually means staying near factory intake/exhaust duration numbers to keep the engine responsive and make power in the RPM range the track demands.

Intake duration is how many crankshaft degrees (or time, depending on how it’s measured) the intake valves stay open during each engine cycle. Longer intake duration generally lets more air in at higher RPM, but it can reduce low-RPM drivability and efficiency.

Exhaust duration is how long the exhaust valves remain open during the cycle. Bigger exhaust duration can help the engine evacuate spent gases at higher RPM, but too much can hurt cylinder scavenging and low-end response depending on the rest of the cam and setup.

The Dodge Charger is a performance-focused full-size sedan that’s known for strong engine options and a sporty, muscle-car style. It often comes up in discussions about power upgrades and driving feel because it has a long history of enthusiast modifications. In a podcast, it’s a natural topic when the conversation turns to getting a car “going” and making power reliably.

An engine dyno measures power and torque at the engine itself, usually with the drivetrain removed. It helps compare engine setups, but it doesn’t include losses from the transmission and driveshaft, so engine-dyno horsepower can differ from what the car delivers at the wheels.

Track “mile per hour” (top speed) is influenced by how much power the car can sustain and convert into acceleration over the run. The host links higher trap speed to higher average horsepower when wind resistance and vehicle weight are similar.

“60 foot” is the elapsed time/distance to cover the first 60 feet of a drag strip launch. It’s a key indicator of traction and launch efficiency; however, the host argues that a faster 60-foot doesn’t always translate to higher top speed at the same elapsed time later.

The “eighth” refers to the eighth-mile drag strip segment (about 660 feet). It’s a common reference point for how the car is accelerating after the launch, and the host is discussing why trap speed can drop even when the early 60-foot improves.

In an automatic transmission, the torque converter can be “unlocked,” meaning the engine and transmission aren’t mechanically coupled as tightly. That increases slip and can reduce drivetrain efficiency during low-speed launch, which affects how effectively horsepower becomes wheel power.

“Heat soaking” means the engine absorbs and retains heat, raising temperatures beyond what you’d see at the start of a run. The host suggests that extra heat early (during the first 60 feet) can reduce how efficiently the engine makes usable power later in the pass.

When the torque converter is “locked,” the transmission engages a mechanical coupling to reduce slip. That improves drivetrain efficiency so more of the engine’s horsepower can be delivered to the wheels, especially in higher gears later in the run.

“Time under power” is the duration during which the drivetrain is effectively applying torque to accelerate the car. In drag racing, more time under power can improve average acceleration and help translate launch behavior into higher terminal speed.

The Cadillac CTS V is a performance sedan known for high-output forced induction and track-focused tuning. In this context, it’s mentioned as an example of a supercharged platform where camshaft design can be optimized around maintaining boost for fast drag results.

Whipple is a well-known supercharger brand, commonly associated with high-boost performance builds. In the context of the episode, a larger Whipple supercharger is used to explain why cam overlap can behave differently when the engine is no longer air-limited.

Pumping losses are energy the engine spends moving air through the intake and exhaust system, especially when pressure differences are unfavorable. The host argues that better scavenging from valve timing and forced induction can reduce these losses, improving power.

Scavenging is the process of using airflow and valve timing to help clear exhaust gases out of the cylinder and bring in fresh charge. The episode links scavenging to cam overlap and forced induction, especially when the engine is not air-limited.

“Air limited” describes an engine setup where the limiting factor is how much air the engine can ingest, not how much fuel it can burn. In that situation, aggressive valve timing (like more overlap) can reduce effective cylinder filling and waste potential boost or scavenging benefits.

Average power refers to the mean engine output over a relevant RPM band, not just the single highest peak. The host claims that the driver who makes the most average power in the RPM window they use will likely be the one going fastest.

An RPM window is the band of engine speeds where the car spends most of its time during a run. In racing, the “best” cam or head isn’t necessarily the one with the highest peak—it's the one that delivers the strongest average power where the engine operates.

A peak number is the maximum value of a measurement—like peak horsepower or peak airflow—at one specific operating point. The host argues that racing results depend more on how the engine performs across the operating range than on marketing-friendly peak figures.

“Area under the curve” refers to the integrated total flow (or power) across a range of operating points, not just the maximum at one point. In cylinder-head comparisons, a head with slightly lower peak flow can win if it flows more consistently across the valve-lift range that the engine uses.

Torque is the twisting force an engine produces, and it’s often what determines how quickly a vehicle can accelerate, especially from a stop. On a dyno, torque is measured across engine RPM, and higher torque (at the right RPM range) can help a diesel launch “out of the hole.”

A “block” is the engine’s main structural casting that houses the cylinders and supports the crankshaft. Saying it was an “essentially stock 67 block” implies the engine’s foundation wasn’t heavily modified, while other parts (like the cylinder head) were upgraded—an approach that can balance cost, reliability, and performance.

“Common rail” is a diesel fuel-injection system where fuel is stored under high pressure in a shared rail and then delivered to each injector as needed. It enables more precise injection timing and multiple injection events, which helps support higher power levels more consistently than older systems.

In this context, “forge” refers to using forged pistons (pistons made from forged metal) rather than cast pistons. Forged pistons are typically stronger and can tolerate higher cylinder pressures, but the host is suggesting that for this power level, factory pistons may already be sufficient due to clearance and proven results.

Piston wall clearance is the designed gap between the piston and the cylinder wall. Too little clearance can cause the piston to scuff or seize as temperatures rise; too much can reduce efficiency and increase wear. The host is arguing that factory pistons have enough clearance to avoid issues when pushing power.

High compression refers to increasing the engine’s compression ratio, which raises the pressure and temperature of the air-fuel mixture before ignition. Higher compression can improve efficiency and power, but it also increases the risk of knock/detonation and can require stronger components and careful tuning—especially under extreme diesel racing conditions.

A deck plate is an aftermarket engine component used to alter the effective combustion chamber volume and/or compression characteristics by changing the piston-to-head relationship. In performance diesel builds, it’s often part of a strategy to increase compression and control combustion under high boost and fuel delivery.

A “big cam” means a more aggressive camshaft profile (typically more lift and/or longer duration) that changes valve timing and how long the valves stay open. In diesel racing, that can improve airflow and combustion efficiency, but it also increases mechanical stress and can complicate tuning and durability.

Valve relief pistons have notches (reliefs) in the piston crown to provide clearance for valves. They’re commonly used when cam timing, valve lift, or cylinder head modifications increase the chance of valve-to-piston contact, allowing more aggressive cam setups without interference.

To “atomize” fuel means to break it into a fine mist so it mixes with air effectively. Poor atomization can lead to incomplete combustion, higher soot, and less efficient power production—especially when pushing very large injector duty cycles or fuel volumes.

Top Fuel is a class in drag racing (NHRA/dragster) known for extremely high power and short, intense runs. The host references top-fuel engine cylinder heads and port quality, arguing that in that world, durability can matter more than maximizing flow numbers.

In cylinder-head context, “ports” are the passages that guide air/fuel into the combustion chamber (intake ports) or exhaust out (exhaust ports). Port shape and surface finish affect flow and mixture quality, but the host claims top-fuel builders may accept “crappy” ports if the engine still survives.

“Small block Mopar” refers to Chrysler’s compact V8 engine family (Mopar is the brand name for Chrysler’s performance parts). In drag/diesel racing talk, it usually means a specific, popular displacement/engine architecture used for high-RPM builds and airflow-focused tuning.

A “horsepower recipe” is a build strategy: the specific combination of engine parts and tuning choices that reliably produces a target power level. The host contrasts chasing peak power with the real goal in racing—keeping the engine alive under repeated high-load runs.

“Valve reliefs” are cutouts in the piston crown (or related geometry) that provide clearance for valves when the engine is built to run higher RPM or different cam timing. In this segment, they’re discussed as a way to prevent valve-to-piston contact so the engine can spin the RPM needed without “crashing valves.”

“Valve release” here is being used in the context of valve timing/clearance at high RPM—how safely the valvetrain can open and close without interference. The speaker ties it to valve reliefs and preventing “crashing valves,” which is a clearance problem between valves and pistons.

The Chevrolet Spin is a compact multi-purpose vehicle (MPV) built for practical everyday use, typically emphasizing space and affordability. In a podcast context, it may be mentioned because the conversation is about engine operation and tuning strategies like controlling engine speed (RPM) and managing valve timing or valve-related procedures. That kind of detail usually comes up when discussing how an engine is built or serviced to achieve specific performance goals.

In diesel engines, “swirl” is the rotational motion of air inside the combustion chamber. It helps mix fuel with air and improves combustion; the segment suggests valve reliefs can disrupt swirl, which can hurt efficiency and power.

“Flux injectors” refers to a specific injector design/brand used to deliver fuel precisely in diesel engines. The segment claims injector nozzle changes (from one style to another) can be tested back-to-back on a dyno while keeping the same turbo, showing how injector spray characteristics affect power.

In diesel fuel systems, a “nozzle” is the injector tip that atomizes fuel into a spray. A “six-hole” nozzle means the injector has six small orifices, which changes how finely and evenly the fuel is distributed in the combustion chamber.

“Short shifting” means upshifting earlier than usual to keep the engine in a more effective power band. In this context, the hosts claim that staying below about 4000 RPM improved elapsed time because the engine wasn’t benefiting from higher speed.

Airflow is the amount of air the engine can move, typically discussed in terms of how much air (often in CFM) reaches the cylinders. For diesel performance, airflow limits how much fuel can be burned efficiently, so airflow matching to engine speed matters more than chasing bigger numbers blindly.

Intake and exhaust valve events describe when the valves open and close during the engine’s cycle. In camshaft design, the timing of these events can matter as much as (or more than) headline cam duration numbers because it determines cylinder filling and exhaust scavenging at specific RPM ranges.

Camshaft design is the engineering of a cam’s profile to control valve lift and timing throughout the engine’s rotation. The hosts emphasize that the “most important event” in cam design is the valve timing (opening/closing events), not just the commonly discussed duration numbers.

The intake valve closing event is the crankshaft timing point when the engine’s intake valve shuts and stops the cylinder from taking in fresh air. Because the piston is moving up and down, closing it too early or too late changes how much air gets trapped for combustion, which directly affects power.

The Dodge Challenger is a performance muscle car known for its powerful engine lineup and strong enthusiast following. It often gets discussed in terms of engine families and how different powertrains behave, especially when tuning or diagnosing issues. References to “Hellcat engine” suggest the conversation is about how specific high-performance variants may respond differently.

“12 valve” describes an engine cylinder head design with 12 valves total—typically meaning multiple valves per cylinder (commonly four per cylinder in many inline engines). The speaker connects this valve layout to cold-start tuning, implying that valve timing strategy differs by head design.

A supercharger is a forced-induction device that increases the amount of air entering the engine by compressing it. The speaker connects supercharger boost/air density to “momentum” of the intake charge, arguing it helps keep air moving into the cylinder even as the piston reverses direction.

Bottom dead center (BDC) is the crankshaft position where a piston is at its lowest point in the cylinder. It’s important for valve timing because what the intake charge is doing around BDC affects how much air/fuel actually stays in the cylinder versus being pushed back out.

Cold starting is the engine’s first start when the engine and intake components are at low temperature. The speaker suggests early intake valve closing could be a strategy to improve starting behavior in cold conditions, because fuel/air mixture and airflow dynamics differ when everything is cold.

Dynamic compression is the effective compression the engine actually achieves based on real valve timing, not just the static geometry. If the intake valve stays open too long near BDC, some of the charge can escape back into the intake, lowering dynamic compression and reducing power.

Compression ratio is the ratio between the cylinder’s volume when the piston is at bottom dead center versus when it’s at top dead center. If the intake valve timing causes less effective compression (for example, by letting the cylinder lose charge), it can reduce cylinder pressure and make it harder to make strong power—especially for starting and low-RPM response.

Valve duration is how many crankshaft degrees the valve remains open during the engine cycle. Longer duration can improve high-RPM breathing by keeping the intake valve open longer, but it can hurt lower-RPM efficiency by allowing charge to flow back out of the cylinder.

Dynamic tuning refers to how intake/exhaust pressure waves and flow timing help “tune” cylinder filling at certain RPM. When valve timing is off (like leaving the intake valve open too long), it can disrupt those pressure pulses and reduce the engine’s ability to make peak power where the system is tuned to work.

Variable valve timing (VVT) changes when the intake and/or exhaust valves open and close, allowing the engine to optimize breathing across a wider RPM range. The tradeoff is that a single fixed cam profile can’t be ideal everywhere, so VVT helps match valve events to the engine’s current speed and load.

Cam timing is when the camshaft opens and closes the engine’s valves relative to crankshaft position. Changing it can improve power at certain RPMs, but it can also affect emissions by altering how much unburned fuel/air and exhaust gases end up where they shouldn’t.

Intake charge is the mixture of air (and fuel, depending on the engine type) that’s drawn into the cylinders during the intake stroke. If cam timing causes it to flow the wrong way, it can contribute to emissions issues and poor combustion behavior.

In camshaft talk, “lobe” refers to the raised profile on the cam that controls valve lift and timing. A “big lobe” cam can sound rough at idle because it’s designed for higher-RPM breathing, where the valve events match the engine’s airflow needs.

“Fuel only” means the car is making power without additional power-adder systems like nitrous. The speaker’s point is that without nitrous, the tuning options for launch and throttle response are more limited, so the car may not hit the ideal power delivery right off the line.

A push rod is a mechanical link that transfers motion from the camshaft to the rocker arm/valve train. Under extreme loads (like aggressive valve timing plus nitrous), push rods can bend, which can lead to valve train failure and loss of engine control.

Studs are threaded fasteners used to clamp components to the cylinder head. In high-load valve-train setups, extreme forces can pull studs out of the head, compromising the rocker arm mounting and risking catastrophic failure.

The rocker arm is part of the valve train that pivots to open the exhaust/intake valve when driven by the push rod. High cylinder pressures and aggressive valve events can stress the rocker arm area, including fasteners that hold it to the head.

Air velocity (often described as airspeed) is how fast the air moves through the intake port. Higher airspeed can help cylinder filling and reduce reversion (air flowing back out) when cam duration/timing isn’t perfectly matched to the RPM.

The coefficient of discharge describes how effectively a cylinder head port flows air compared to an ideal opening. A higher coefficient means the port turns pressure into airflow more efficiently, which can improve cylinder filling and power—especially when cam timing and RPM aren’t perfectly matched.

Top dead center (TDC) is the crankshaft position where the piston is at its highest point in the cylinder. Valve timing is often described in degrees of crank rotation after TDC, which helps predict when the intake/exhaust valves open relative to piston position.

Valve lift is how far the intake or exhaust valve opens off its seat. More lift can increase airflow (and CFM) by allowing the valve to pass more air, but only up to the point where the rest of the head/cam/porting can support it.

The intake stroke is the part of the engine cycle where the piston moves to draw air (or air/fuel mixture) into the cylinder. Valve sizing affects how easily the engine can move that air during the intake stroke, which influences power.

Atmospheric pressure is the baseline air pressure outside the engine. The speaker contrasts it with turbo boost, arguing that without boost you don’t have as much pressure difference to drive airflow through the intake.

Boosting a turbo means increasing the turbocharger’s output pressure above atmospheric pressure. That higher pressure helps force more air into the engine, reducing the pressure difference limitations the speaker says you’d otherwise face.

Valve diameter (like 1.42 inches) is a direct way to specify how large the intake valve is. Larger valves can increase potential airflow, but the best size depends on the head’s port design and cam timing so the engine can actually use the extra flow.

A remanufactured cylinder head is a rebuilt head that’s been disassembled, inspected, and repaired—often including resurfacing the mating surface. The speaker notes that resurfacing thickness changes component fitment inside the engine, which can affect combustion and power.

“Surfaced” refers to machining the cylinder head’s mounting surface to restore flatness. Cutting “10,000” or “20,000” (ten or twenty thousandths of an inch) changes the combustion-chamber geometry and can alter how far fuel components extend into the chamber.

The injector nozzle is the tip of a fuel injector that sprays fuel into the combustion chamber. The speaker claims that after resurfacing a remanufactured head, the injector nozzle protrudes deeper into the piston bowl area, which can improve combustion and make power.

The piston bowl area is the shaped recess in the piston crown that helps direct fuel/air and manage combustion. Injector position relative to the bowl can strongly influence spray targeting and burn efficiency, which is why head machining that changes injector protrusion can matter.