Lots of people are saying not to use this as a two step... I want to use it on my turbocharged trans am.. a lot of the common arguments are:

It will run lean because it's a fuel cutoff, not a spark cutoff

It will damage cats (obviously I have none)


Here's the thing- When a PCM cuts fuel, it cuts it completely. It won't run lean, it'll just pump air and waste the spark, then apply full fuel when it drops below the RPM window. It's like a factory rev limiter (which is safe, for the most part) It sounds safe to me, with my logic. I want to spool my turbo at the tree with the two-step, using Valet mode. How could it possibly do engine damage unless the fueling was leaned out when it comes back on? Trying to figure out the logic behind why I shouldn't use it. Seems to make more sense than dumping raw fuel into my manifolds via a standard spark retard fuel step, and backfiring into my compressor wheel (bearing damage etc)... Thoughts?

 

lingenfelter makes a really good one.

 

That has nothing to do with my question.

 

Well here is the theory behind 2 steps and F/I that most people either don't know or don't realize.

When you are using a 2 step with a turbo it's main purpose is to spool the turbo faster and consistently.

What a spark cut-off 2 step (or otherwise known as anti-lag in the rally world) does is moves the combustion process outside of the combustion chamber into the hot manifolds and crossover. The actual heat from the manifolds and crossover is what ignites the fuel thus creating the exhaust pulses much closer to the turbine wheel and spooling the turbo faster.

It's all about getting the turbo spooled quicker by doing that so I don't see how it will spool any faster with a fuel cut-off than just spooling on the footbrake or t brake. I don't see it being effective for what you want because of how it is "suppose" to work. Now I'm not saying sitting at the tree for 3-4 seconds won't spool it, but your heating tranny fluid up and just heat soaking the motor doing that.

This is just my .02 worth and you can do whatever you want and it will probably work, just not how you want it too.

 

You need a proper 2 / 3 step to do any good with a turbo car. IMO.

 

IIRC
Valet Mode is based off vehicle speed not RPM.

 

Sounds like I need to use a transbrake by itself instead of with a two-step. Thanks for all the input. Shoemike- you are correct, the parameters are only for VSS..

 

No you can use both at the same time in fact that's what you really need to do. Using a 2step and transbrake at the same time will spool the turbo much faster than just using the converter on the trans brake.

As gregrob said you need a proper 2/3 step that uses a spark cut off not fuel cut off for a turbo car to spool on the line like you will want it too.