LS6 Cam Detuning
 

Hi All,

I am building an E36 M3 for NASA ST3, which has a power to weight restriction of 10:1. I tried to do some googling, but have come up short with an answer for my question (probably people withholding information?). I am looking for insight on the ability, methods, results, etc of a cammed LS1/6 being detuned.

The cam I am looking at is the GM ASA cam along with CNC'd heads. This cam usually makes around 410whp and I would have to be detuned to ~320whp. Has anyone ran a combination of a throttle stop (how much), air restriction (what size) and timing detuning?

I'd like to be cammed as I have a theory that would maximize low end torque while staying within HP restrictions at the top end. I'd like to see if my theory is right or wrong. I'd also like to have to cam to run time attack uncorked.

Thank you,

Bart

Going off memory that cam would make you lose low end torque. I would have to look at some old dyno sheets to be sure. Been years since I dyno one of those cams.

What about using the Hot Cam instead? 219/228, .525/.525, 112LSA

Almost any time you need to limit horsepower and you do not have the option of changing mechanical parts, you just need to lower rpm. That way you keep whatever full throttle torque you have available, but the horsepower drops to whatever your torque curve leaves you at your set rpm.

You are able to do as you please with the motor but it cannot exceed 10:1 weight to hp. Limiting RPM would limit me to ~4500rpm. I am looking to see if people have ran a cam with a throttle body restriction and/or throttle stop to make use of all the RPM but not exceed their HP limitations.

Sounds like to me you should be putting a solid bolt on high out put 5.3 in it instead of trying to tune 150whp out of it.

If you really need the rpm range more than torque, I would suggest a 4.8 as a better choice of motor.

We have been building engines for restrictor racing for 20 years. That cam is all wrong for what you are trying to accomplish, as are the others. You are going to need something like a 210/220 on a 107-108. You'll need something around a 60mm restrictor if using a 78mm TB to hit your rwhp goal of 320.

You cant really have one cam to do both. The cam that shines under 6k rpm with a restrictor wont be ideal for un-corked time attack.

Thank you, this is the kind of information I am looking for. Can you elaborate on some details of the restricted motors you have built? What torque are they making? Do you know gearing if they are being raced?

I am using a 5.7 because that is the motor I have been using, it is currently making 375whp and 360wtq on the stock ls6 setup.

It would be super easy to do in the tune, even adjustable on the fly with a potentiometer to make whatever power you wanted.

We have done everything from 2.0L 4 cylinders to 5.0L V12 and everything in between. Gearing all depends on the track. There was a 6.0L V8 we used to do that made about 600ft/lb through two 28mm restrictors. And if memory serves me right, the old C5R 7.0L engine made about 600ft/lb through two 25mm restrictors.

I imagine its not legal to be done with just the tune unless there is a stipulation in the rules for a sealed pcm.

Which would be perfect because you could have that pcm to be tuned to 310rwhp with the rev limiter set to 5k (or somewhere lower most likely) and then for time attack stuff slap in another pcm that revs out and is tuned for the cam you want to use. Restrictor racing is all about torque since when the rules are applied properly everyone is just as fast top speed. Its all about reaching terminal velocity the fastest.

I am drive by cable, so I can not do any trick throttle plate tuning... Tho I wish I could!

We can have multiple tunes on one PCM, we just have to show dyno plots for each tune. If I am protested then I go straight onto a dyno after the race to verify HP on the spot.

So, from your experience, an LS6 with a cam/heads/intake can be detuned to ~320whp (and whatever TQ number) by a combination of throttle restriction, restrictor plates and timing detuning? I'd like to not reduce working RPM unless I then gear down my final drive to a 3.38 (from my 3.91).

Thank you Jensen!

Nothing I suggested required throttle plate tuning. I am talking about the actual tune in the ECM that controls spark.

Well that makes it easier. Just flash and go for each style of racing.

There are many ways to achieve what you want.

As spider has said you could do it with tune only. My only concern there (without limiting rpm) would be egt's as you would be pulling a lot of timing to lose 100ish horsepower. Why I suggested an RPM limit.

Throttle stop setup. Essentially the same thing as a restrictor.

An actual restrictor. Best place to put it is right behind the air filter and as far from the TB as possible. We have some right behind the TB too though, all depends on the space available

Fuel flow. Not what youre after but a great way to restrict power by sanctioning bodies

Find a really stingy dyno...