At the Optima Ultimate Street Car Challenge, Jake shares insights about his impressive naturally aspirated C5 Corvette, which boasts 800 horsepower without forced induction. He discusses the benefits of a big cubic inch engine, the importance of weight distribution, and the unique adjustable intake manifold that enhances performance. The conversation also covers engine management choices, including the use of a GM ECU for better drivability, and the switch to a BMW ABS system for improved braking reliability. Jake's experience highlights the advantages of innovative engineering in competitive racing.
Jake Rozelle's C5 Z06 Chevrolet Corvette is no stranger to the Optima Ultimate Street Car Invitational having taken victory previously in what is a well setup street driven race car. The 800hp (to the crank) 7.2L/440cu Lingenfelter Eliminator R Spec LS7 contains forged rotating assemblies, CNC-ported cylinder heads, competition-grade fasteners, precision balance procedures & hydraulic roller camshaft internally, as well as a Dailey Engineering dry sump, Performance Design intake manifold with some tuning being done to the intake runner lengths over time. With just oil changes over the last 2 seasons of racing it certainly seems to be a package that is working well for Jake in this application.
The hydraulic cam profile is in its element with the 8,000rpm redline being within the comfort zone and the 14:1 compression engine runs E85 via a flex fuel setup in street form and Ignite Ready 90 on race day. Engine management is done by a GM ACDelco E92 ECU from a later model vehicle of the Cadillac CTS-V & Corvette C6 ZR1 era.
While an advantage of retaining a OEM GM ECU originally was the ability to keep features like the stock ABS system, Jake has since gone the popular route of fitting an aftermarket/standalone $1200 MK60 ABS system with an off-the-shelf tune from CSL Performance and he gives us some insight into the installation and use of such an ABS system which are becoming more and more popular at club level racing despite the initial push back from the good old armchair racers we've seen over the years.
"...ewer C6 ZR1s and newer CTSV Cadillacs. So it's an E92 GM ECU. It has a lot more capability the higher t..."
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We're here at the Optima Ultimate Street Car Challenge, and behind me is this purple C5 Corvette.
This won the competition outright last year.
However, the interesting aspect from my perspective is in the sea of cars running forced induction, this is naturally aspirated.
We're here with Jake, the owner and driver of the car, to find out a little bit more about what makes it so fast.
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So, jake, first of all, the engine combination.
Here, forced induction seems to be everywhere in this car park at the moment.
You've obviously proven it's not necessary, but what was the driving decision around staying NA?
It's really fun to drive NA and it's a big cubic inch motor so we still make the power.
We went big displacement instead of going big turbo or big supercharger, and it keeps the car light.
We had a handling competition.
At the end of the day, all the segments involved handling and this car has a perfect 50-50 weight bias at the moment and if I did have to put turbos or a supercharger it would affect that.
Okay, fair enough In terms of the power you're making, it's still no slouch.
What's it produce?
Yeah, so it's a Lincoln filter built illuminator series engine about 440 cubic inches making 800 horsepower at the crank.
That's a pretty healthy combination.
Can you go into a little bit more detail on that engine combination?
What is the sum of the parts there?
What's it running inside?
Sure, yeah.
So it's, as I mentioned, 4 and 40 cubic inches.
It's got a daily engineering dry sump on it, so it's an externally driven dry sump system.
Langenfeldt put together a forged rotating assembly for the car and it's actually still a hydraulic roller camshaft.
We're only revving the car to only 8000 RPM, which for that big of an engine is still quite a bit.
But the nice thing about having a hydraulic roller is this is a street car series.
I'm not lashing valves to take the car to dinner and it's really maintenance free.
I really have just changed the oil in the car for the last two seasons.
On top of the motor we have a performance design intake manifold.
The nice thing about that manifold is you can actually change the intake runner lengths really easily.
We do a lot of that to change the power delivery.
Right now we have a little more bottom hit than we did last year and I really enjoy the mid it gives me on the autocross especially and on the road course.
This morning I'm able to carry a gear higher than I was last year, and all we've changed was some things in the intake manifold 102mm throttle body and then a custom 4.5
inch cold air intake system that picks up underneath the headlights.
OK, let's go back to that inlet manifold.
You mentioned the adjustable length inlet runner, which I imagine is not overly common.
I haven't seen anything like that before.
The old theory, or the general theory, is, the longer runner improves the bottom end performance, shorter runner improves top end performance.
Obviously there's a lot more to it in terms of the specifics, but are you actually changing that runner length based on what you're doing, an autocross style event or something?
Road race, that's a little bit faster.
I'm not changing it that often.
I'm changing it maybe once or twice a year.
We did the dyno data at Lincoln Felter to see what it did and then I drove the car because, as you mentioned, there's a lot more to it than just numbers.
So I drove the car and what I felt actually reflected the dyno, and that is I liked the mid power range and I felt that it's been the same for the last year.
And the other thing is when you're dealing with intake runners, the throttle body is in the front and the intake runners go from front to back, so it's not even necessarily that it's just the length, it's where it's at in the position and that also affects whether you want a short or a long.
We're not running uniform runners is what I'm getting at.
OK, fair enough.
As I said, there's a lot more to it.
It's not particularly black and white, but I just wanted to dig into that a little bit.
You also mentioned the hydraulic roller cam profile.
So hydraulic versus mechanical?
You also alluded to the fact that mechanical cams need the valve latch checked and adjusted at a reasonable frequent sort of intervals.
Are there any downsides in you sticking to a hydraulic cam profile?
If we want to rev the car higher, yeah, but at 8000 RPM the car does over 70 miles an hour in first gear it carries power from 4 all the way to 8 grand.
I have the power band I need.
Compression ratio.
So obviously one of the big elements in getting the best performance out of a naturally aspirated engine and within reason.
Again, there's not a lot of black and white here, but higher is generally better.
But of course then we come up against the octane of the fuel available.
So what are you running in terms of compression?
Yeah, I'm running a little over 14 to 1, as mentioned, with octane.
That pretty much puts me at E85 most of the time, unless I want to run race gas For a road course application like today.
I run the Ignite Ready 90, which is rated a little over 110 octane, and the car absolutely loves that fuel.
It's never had a miss.
It's pretty amazing.
On a fuel that good with 14 to 1 compression is not even a consideration.
Or are you able to tune to MBT with no concern about detonation?
It really hasn't been a concern.
That would be expected.
Now you are flex fuel there as well, just pump gas for getting around in between tanks of ethanol, or do you actually run it hard on pump as well?
I never run it hard on pump.
It's just not worth the risk to me At a car like this, even if I'm taking it to dinner.
It's worth the extra six bucks or whatever it's going to be a gallon, just to be on the safe side.
You never know when you're going to get on it.
I think it's called smiles per gallon.
When you've got a car like this, correct Exactly Engine management.
What are you running there?
Yeah, so we stuck with a GM based computer.
It's what comes in the newer C6 ZR1s and newer CTSV Cadillacs.
So it's an E92 GM ECU.
It has a lot more capability the higher toothed reluctor wheel that didn't come in the C5 generation Corvette.
It allows us to run that now.
It has a lot of functionalities, like that flex fuel, along with additional tables to control boost which we can use to control maybe things in the future like nitrous, if we ever have to.
We haven't had to yet.
Right now we're doing pretty well.
So if we ever have to, this motor could easily handle another 200 shot of nitrous and it is something that's in our back pocket.
That decision with a competition based car to run factory engine management.
And again, it's very difficult now to say this is a point where we must go after market, but I imagine most people in your situation would have picked an after market standalone.
So what made you want to stick with the GM controller?
We definitely looked at the after market a lot and we looked at numbers people were making with them and I do a little bit of tuning, but primarily Lingonfelter does my tuning.
They really like the factory style for their customers because it's simple.
A lot more folks know how to tune it and use it.
So what made me go with it was they were developing a new system that allows you to basically plug and play into this car that new ECU system.
It allows you to maintain your factory ABS, it allows you to use your factory fuse box.
It's all plug and play and goes right into the car and now you have all the benefits of the new ECU.
So this was the first car that Kit went on and when they approached me about it it was when I was already looking ECUs anyway and it made the most sense and drivability's been awesome and you know a factory ECU does do that very well and it's been one of my favorite parts about this car.
I think people sort of tend to believe they need to jump to an aftermarket stand alone really early on in the piece, and you've proven that it's absolutely not the case.
And the other part that's easy to sort of ignore with an aftermarket stand alone is this one ECU is designed to be able to run thousands just about any internal combustion engine that you could come across, so the strategies are very universal, whereas when you're dealing with a controller from GM, that's very narrow focused.
All of the strategies, tables et cetera, are developed around getting the best performance out of that engine.
So quite often drivability, as you mentioned, can be easier to get right and better than some of the aftermarket stand alones.
You also mentioned the ABS system there and this is quite interesting.
I wanted to dive into this because you're no longer running the factory ABS, even though, as you mentioned, you could.
What have you gone to?
Yeah, so I swapped two years ago to the BMW MK60 ABS system.
It's kind of the budget alternative that you always hear about on the internet and it was really simple.
I'm in the whole system for maybe $1,200, which compared to a Bosch where you're looking at close to 10, which I would love to have a Bosch it's definitely, definitely gets you the more performance.
But from the factory these cars are really known for, when you get into slippery conditions, especially with big tires, big brakes, the ABS gets confused, you get a hard pedal and it's a little unpredictable.
The MK60, I had the CSL performance tune put in it.
I know you can custom tune them.
I've looked into that.
I still might but it got rid of all the weird quirks that the car had from the factory at the ABS and now when I go to the pedal, I know exactly what I'm getting every time.
So is it a full motorsport unit?
No, but does it work really really well for what I'm doing?
Yes, OK, let's just talk a little bit more about what that system is and where it comes from.
This is available on a range of different cars, primarily BMW.
Yeah, primarily BMW.
I want to say 90s, early 2000s, M3s, and the reason it's special is because it's really standalone.
Most ABS units like what come in this car.
They need to speak to all the other units in the car, speak to the BCM and that unit is standalone.
I have its own check engine light for the ABS system, so a check ABS light, basically, and it doesn't speak to anything else.
It's plugged into my dash that way and other than that it needs no data.
So, in terms of adding the sensors that are required, is this a case of just buying a package of the MK60 ECU pump, et cetera all of the wheel speed sensors and then making up a harness in between?
Essentially yes, mounting the unit.
It needs pressure from both front and rear lines.
So putting that in.
And then the newer style Corvette so 2009 and newer, I believe that switched to Bosch style sensors.
That hub works with the MK60 and that hub bolts right into this generation Corvette.
So you just need to buy the newer style hubs and then you can run an MK60 and just use your factory sensors and just splice it in.
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So I know that a lot of people watching right now are probably on the edge of their seats, worried about your health and safety and the reliability of this aftermarket.
Will standalone ABS unit that you've put in a car that was never meant to be in?
When I get the concern?
Obviously you're dealing with a mission critical component here with the braking system.
We want to rely on it.
So you're telling me that that's not an issue first and foremost and what you have got is significantly better than what the factory Corvette braking system was.
I would say significantly safer, not just better, it's just knowing what I'm gonna get here at this course.
It's a really long back straight away.
We're well over 150, 160 ish mile an hour and it's a high speed right that you barely slow down for and the car would get light and with the factory ABS you would go to the brake to drag it through the corner and the right inside wheel would detect a little bit of a lock up and then the pedal would get rock hard on you.
Now you're in the middle of this high speed sweeper where you need control of the brakes and now the pedals aren't.
And this system has never even hinted at anything like that.
It's been just very predictable, which in my mind means safety.
Yeah, I get that.
It makes perfect sense to me.
We are going to be testing this system in one of our own in-house project cars because we've had a lot of people, both pros and cons of the system or foreign against the system.
We want to get some actual hard data on it and find out for ourselves.
Now, interestingly, as part of that, I did notice you actually do have a residual pressure or pressure reducing valve plumbed into the system as well.
So the ABS system acts as a bias, essentially biasing the pressure front and rear, as it's required.
So I'm interested to know why you've also got the mechanical valve there.
The mechanical valve's.
There again, the nice thing about the system is it doesn't need the other system.
So if I ever did have an ABS failure, I have a switch in the car to turn the ABS off and now I can adjust using the mechanical bias where the factory ABS system, if it went out, it put the car in reduced power mode anyway, but there was no way of really stopping.
The factory bias is basically undrivable in these cars.
You need some type of adjustment.
So now I have the better ABS and if something does go wrong I have a way to still drive the car.
I grew up driving cars without ABS.
I would be okay.
So I mean, it's not going to stop as well, but it's going to at least get you back to the pits.
Oh no, I would still race.
It would be fine In terms of the performance of the ABS system as well, because this is another element where people will sort of say, well, it takes away from the driver involvement and absolutely it does In terms of the people who want to say, well, the ABS system can't break as well as a competent driver.
Have you got any sort of pills of wisdom there?
Yeah, you are a one channel brake system.
When you let off the brake pedal, all four brake calipers release and when you get on the brakes, all four go.
This is a four channel ABS.
So if I'm on an autocross which is where I more have these types of situations and you're straddling two different surfaces which happens all the time in autocross and one side is much dirtier than the other, or maybe one side got rained the day before and washed things on to it and the other side didn't get dirty, now you have way more braking on one side of the car than the other, and this can adjust for that or that high speed sweeper I was mentioning, where the right rear inside gets light, it can not apply as much pressure to that one wheel and apply more to the outsides.
You can't do that as a driver.
I think the argument that I always hear about ABS is that a really good driver can stop faster.
I mean, yeah, if you're Max Verstappen or Lewis Hamilton, then chances are.
Yeah, you probably can, but we aren't.
And, as you mentioned there, the variable conditions as well, it's not a case of stopping perfectly as quickly as you can under perfect conditions.
We're not under those conditions, so the ABS can, in most instances, do a better job.
You'd agree with that.
Max would have ABS if he could.
I like Max, he's a hell of a driver.
He would have ABS if he could, because he can't again control all four wheels at once and a computer can In a flat road on perfectly grippy conditions.
Yes, could he probably outbreak any ABS?
Sure, but you're never going just straight on the brakes, not on a road course.
And we're probably not expecting a contract anytime soon from Red Bull Racing, so it's probably a bit of a moot point.
Look great to get some inside into the car, and it's only part way through the competition.
We wish you all the best for backing up your win from last year.
Cheers for your time.
Yeah, thank you very much.
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