I have been hearing talk about a "2-step" launch that people are starting to talk about on the Redline forums and I wanted to inform you guys before you go and make mistakes.

Apparently someone ont he Redline forums thought they figured out how to make a 2-step launch control for the car, by using the PARK/NEUTRAL Fuel Cutoff to limit the rpms when the clutch in engaged.

DO NOT DO THAT!

That will cut off fuel as soon as you push in the clutch, even between gears, as long as you are above those RPMs.

So here is my experience with that, because I tried that over a year ago and it had horrible results:

You launch and take off, then shift at 7,000rpms. As soon as you push the clutch in your fuel cuts off like you hit the rev limiter, except it stay cut and the motor temporarily shuts off, then you let the clutch out and the car bogs and pops and then lurches back to life as if you had stalled it. It will hurt your times, ruin your fun, and make you think something is going to blow up.

 

Sounds fun. So what was the intended result?

 

The intention is to make a "lazy-ass" launch control that allows you to just keep the pedal full throttle when at the light, and it will hold it at the RPMs you want to launch perfectly at, and then you just give the clutch pedal a drop and start moving. Works great on the launch, but I race for more than just 1st gear.

 

Those doing it on the redline forums don't run street tires at the track therefor have no problem with the PCM controlled 2 step.

 

I don't care about the launch, I'm talking about the fuel cut in between gears. It cuts the fuel off during shifts if your rpms are above the set RPM. Try it, and I bet you will want it off ASAP.

 

Only if you set it low enough for the PCM not to recover. The guys on the redline forums doing it have slicks and setting their launch rpm much higher than people here running street tires, thus the reason their cars don't shutoff.

 

Fuel Cut 2-Step FTL

IGNITION (Spark) CONTROLLED 2-Step FTW!!!

 

I don't see a big difference.

 

what ever happened to brain control of ur right foot?!

 

Consistant times for bracket racing.

 

um...we run consistent times here without a rpm control..

 

It can only get better with mechanical intervention.

 

There was a huge thread on this over on SVTPerformance.com

With a Fuel Cut 2 step... it bounces of the step really slowly.

The ignition 2 step will actually kinda hold it right at that rpm.

I'll see if I can find the thread.

I'm pretty sure people were posting better times after switching to the Ignition Controlled.

 

true but then ur not really driving the car...i guess i should convert to paddle shifters lol..

 

You can control the rpm window in which it fuels and cuts with the stock pcm as well although ignition would be faster, enough to get a better launch? Not sure.

 

I'm just saying it doesn't work as they are advertising it. I didn't launch at 4500rpms, and even then that's still pushing it.

 

It works fine for us which is why I'm not sure where the problem is.

The only things I can think you are doing is granny shifting/daily driving the car with a two step enabled or setting the two step below 4k or so, not allowing the PCM enough time to recover from a fuel cut status before it stalls.

I guess your results may vary.

 

Yeah I had the P/N limit set lower than that. It caused all kinds of problems with hesitation. And I would shift with my foot in the gas after 1st gear.

 

it was one of your cobaltss cobalts. don't blame us

 

Hahahaha didn't even know that. I figured it was just someone from your Rubbermaid Brigade.

 

hmmm, still never tried it, but I was going to once I get my clutch in since I need to somehow build boost at the line. I was thinking of setting it to 4200-4500 with a 5 rpm drop off. I'll see what happens, if not, it's msd time

 

not proven yet.

I was the one that did it and I launch above 5K rpms with MT ET Streets at the track. Works fine so far on the street. I haven't tested it at the track yet. I was also trying to get a harder launch as I will be able to launch with the pedal floored and I was building 10psi of boost instead of sitting in vaccum. When I get back from my deployment I intend to test it out.

 

You can't control the RPMS resume. It's a temperature controlled park neutral rev limit.

I proved it doesn't work set at a normal rpms. 5k is rediculously high, obviously not intended for street tires.

 

hmm I'll figure something out, maybe off a switch or something cause launching with the turbo is gonna be a pita unless I have something to hold an rpm on the line and build boost.
eh I'll try it out this weekend since the cobalt will be sitting in the garage for a while

 

I need a 2 step for my car