PCM Question

[BigsViper]

I had a friend over yesterday checking out my Viper. He's been drag racing for years and the first thing he asked me was if I had upgraded the PCM. (He's not a Viper or Mopar guy) When I told him no because what I had read here that there was very little benefit without other heavy mods, he looked at me funny.

I did a search and got 83 results. Reading some of them again confirmed my original statement. I found some stuff like Steve Ulligger in the 9's with many mods but the stock ECU, and a few threats and promises for better technology to come, but little proof. There was a post by Sean Roe about the VEC1, but the dynographs were posted on Photopoint so were no longer available.

So my question, is there any HP benefit to changing the ECU (or is it PCM?) if you just have tubes, filters and muffler delete? Or does it just fix the check engine light for catless systems. Also is the engine controlled by the Performance Control Module (PCM) or the Electronic Control Unit (ECU)? Thanks

 

[Tom and Vipers]

A simplistic way to put it is the computer and engine control systems are basically a carburetor and a distributor that you cannot adjust.

What was the 1st thing you did when you got your 1st car?

Advance the timing to pick up a seat of the pants performance improvement.

Then, the mechanical advance springs and weights.

Of course, once you have the ability to program your computer, you can now have advance curves that were impossible to obtain in the stone age.

Then fueling is another matter.

At low throttle settings, you are in closed loop in which the engine is running off the O2 sensors. This responds pretty well to small mods.

At WOT, you are running open loop off of tables stored in the computer. I do not know what params are used to determing injector pulse width, however, if volumetric efficiency is changed substantially, there could be fueling problems.

This is where the work is done especially with NOS and super/turbo charging.

I'm about to buy LS1 Edit for my 98 Z28 so I can do my own programming. If you want to get a taste as to what you can do regarding programming, go to

www.carputing.com

and download their manual for LS1 Edit.

It will answer a lot of question and of course, generate more.