Building boost off factory rev limiter (pomofo's two step)

[dville_gt]

If anyone remembers a while back I found the pin out on which wires to ground to make my PCM in my swap car know if I was in P/N or in gear. Now that I am building a turbo setup I am looking for a two step solution. There are a few out there (MSD, Synergy, etc.) but what about the factory PCM rev limiter. Through HPTuners I can set a limiter for Park/Neutral and a rev limiter for in gear.

So my question is if the factory rev-limiter works in the same fashion as a two step rev limiter. From what I understand the MSD/Synergy/etc. just drop out spark to cylinders to keep the revs at under the limit, is this not how the factory PCM works as well?

[dville_gt]

This is a 0411 PCM out of a 2004 Chevy Express Van btw.

[dville_gt]

after doing some more research it looks like this only cuts fuel, not spark. not sure how bad that'd be on a turbo app, on one had it cuts the fuel for the entire stroke so i dont think it'd cause detonation (no fuel, no boom at all), but if i ran meth it could be a big problem.

[91CoupeMike]

Ever heard of pomofo racing?

[2165 Turbo Rail]

there is a 2 step avail for the LS1's for around a 100 less (I'm thinking its like 80) I'll see if I can find it

[2165 Turbo Rail]

I was wrong... its about 200

http://www.ws6project.com/user_stor/...c18132571581c0

[dville_gt]

Ya, looks like I'll just buy an MSD 2 step, at least I can add a 3rd step if I get a brake at some point.

[turbostang]

after doing some more research it looks like this only cuts fuel, not spark. not sure how bad that'd be on a turbo app, on one had it cuts the fuel for the entire stroke so i dont think it'd cause detonation (no fuel, no boom at all), but if i ran meth it could be a big problem.

Fuel cut is NO problem, it works fine - done in megasquirt land all the time. It just sounds a bit different than traditional spark cut. Search Youtube.

As for the meth, no problem there either - if you want it OFF while on the fuel cut, simply put a hobbs switch and a relay to keep meth from spraying while trying to build boost. (your likely to be at such a low boost the meth won't be coming on anyways....)

[dville_gt]

Finally some good news on the saving money front!

[dville_gt]

Also, I got to thinking.

If/when I get a transbrake, I could use this method as a 3 step as well. HPTuners lets you set a rev limit in each gear as well (1-4 since my tune is based on an auto). By grounding specific pins on the PCM the PCM can tell what gear it is in, like PIN A and B is park, PIN A B C is gear 1, PIN A and C is gear 2, etc. so if I wanted to set a 3 step I could just use a switch to ground pins for the first limiter, then ground pins for the 2nd limiter, and when no switch is pressed it'd be on the standard rev limiter.

[2165 Turbo Rail]

doesn't sound confusing at all

I'm lazy, I'd just spend the $200 and buy one haha... but with this 4L60e I don't want to do anything extra to try to break an already week transmission

[dville_gt]

doesn't sound confusing at all

I'm lazy, I'd just spend the $200 and buy one haha... but with this 4L60e I don't want to do anything extra to try to break an already week transmission

i heard the 4l80 isn't as week, it's month stronger

it really isn't that confusing, but since my pcm doesn't control the transmission anymore seems like a good option vs. 240 for a msd unit. i'll at least give it a try and see how it works.