A friend of mine has a 91 MR2 non-turbo. He and all his MR2 buddies say that when you mod a car (ie header, exhaust, even a damn air intake, etc) you wont actually get much of an improvement in power until you reset your computer. You do this by disconnecting the battery for like 45 minutes or something. Once it is reset, the computer then optomizes fuel maps, etc with the new mod, thus making the difference in power.

Now, I have read alot, I have been around and talked to many a seasoned auto mechanic. I have never heard of this. The mechanics i have talked to say this is BS. Does any one here know the TRUTH! hehe

Thanks in advance for the help

 

There is a "Computer........" forum, and that's where this post belongs... it will be moved there.

I really don't know much about the specifics of an MR2 ECM, but in general, the main data stored in the ECM is the long term fuel corrections. While these corrections are deveolped based on a specific engine configuration, they will start to respond immediately, as soon as you start to drive, to anything that would change the A/F ratio from the target value. In a "mass air" configuration, the response of the ECM would be reasonably accurate. In a speed-density setup, the response may not be as complete, when the change is more radical, like a major cam change. But both will respond and start to develop new long term corrections immediately. You do not need to reset the ECM.... resetting it will only alter how quickly the ECM responds... and resetting it may make it take a little longer.

When you disconnect power from the ECM, the only thing that is "cleared" is the data stored in volatile memory. In the 3rd and 4th Gen F-Bodys, that is primarily the trouble codes, long term fuel corrections and the learned idle position. You can "clear" these with a simple 60-second power disconnect. Then the ECM has to start developing a new set of LT corrections. If you made a minor change to an engine that had already been altered significantly, "clearing" the LT corrections would probably be a setback until the ECM could adjust.

But we're talking instantaneous response here. The only thing that extends the "learning" period is the fact that there is a "grid" of cells for lont term fuel corrections, set up as a function of RPM and engine load, and you don't start to change a particular cell until you actually drive under those conditions.

Not to say there isn't some oddball features of an MR2 non-turbo ECM that might alter this statement slightly, but I doubt it.

Moving.....

 

Thanks for the help. I asked the question pertaining to both F-Bodys and MR2s

Sorry for the Mis-Post

 

Injuneer pretty much summed it up with what he said, but just to add one more thing, there isn't going to be anything in the MR2's computer that will automatically set itself to change to any type of mod automatically. The only thing that will change is what Injuneer said, long term fuel corrections, learned idles, and trouble codes. It's just like when you reprogram a computer with a new program. You erase all the old information in the stored memory that dealt with long term info. PCMs are set up like this so incorrectly long term information doesn't interfere with new programming. Adding something like a CAI or other simple mods really doesn't call for a computer reprogramming, but something like a cam certainly does. But resetting the computer really won't do very much.