Adaptive Learning Reset at the Track

[elcobra44]

Is pulling the fuses to reset the PCM good for getting an immediate positive response from the car at the track?

Lets say it takes me an hour and half to get to the strip, and I cruise up there at a steady 65 miles an hour. Assuming the car has learned to put-put around over the last few hundred miles, I pull the fuses and reset the PCM.

Is that a good move, or is it better to allow the car some time to relearn the hard driving behavior before I run competitively.

I'm not sure if we have a definitive answer, but does anyone have an opinion based on your experiences? My experiments were inconclusive. :confused:

This is a recent debate among us LX'ers in the club.

[WickedSRT8]

Well, I can only tell you what the service manual says... it indicates that there is no adaptive learning done at WOT (or any open loop modes). It works off of pre-defined tables.

That being said, in the past tuning PCMs, I have seen LT fuel trims being carried over to WOT... basically, if you are in a mode where it is adding fuel, and you nail it, that fuel addition will be carried over into WOT. If it is removing fuel, it will not carry that in. Only when adding.

At the strip, you are starting from a dead stop, and generally, I don't see a lot of LT fuel trims at idle on past cars. You load the converter, you might get a trim carried into WOT. This was usually very minor, and wouldn't really effect much of anything at the track. Maybe .1 better... but every little bit helped. Spent a great amount of time messing with stuff to get no fuel trims at all at where I loaded the converter. Finally got there, so never had to reset the PCM.

Plus, resetting the PCM you lose the emissions tests that it does, so if you have an emission test, and your location does OBDII testing, then you might not pass if all the tests have not been completed. Plus, it resets any stored codes, so it might make it really hard to diagnose an intermittent problem.

I am not a huge fan of resetting the PCM, but others say it really works on these cars. Personally, I reset my PCM on a dyno and lost 40 HP... took about 20 miles of driving for it to come back. Was running really rich across the board... so, something goes on, but in my experience, it's negative.

[Manris]

Is that a good move, or is it better to allow the car some time to relearn the hard driving behavior before I run competitively.


If anything I think this would be the way to go. I've read about some owner's that have lost 20-30hp on a dyno pull due to resetting the PCM, but then again I can't remember to what extent their modifications where. So your mileage may vary.

[maneval69]

Here we go again.
The learning only occurs in closed loop but what the PCM learns is applied to all modes of operation even WOT. According to the service manual.
So while it does not make any adjustments or record any data during WOT conditions, all the adjustments affected by the Long term adaption are applied over-top of the WOT tables. If resetting the PCM eliminates the long term adjustments then the WOT program is also cleared of these adjustments.

That being said,
Clearing the PCM still does not mean that you will gain anything. You could actually loose some power because the PCM has not accounted for the conditions that the engine is running in. (altitude, temperature, gas type)

[WickedSRT8]

Here we go again.
The learning only occurs in closed loop but what the PCM learns is applied to all modes of operation even WOT. According to the service manual.
So while it does not make any adjustments or record any data during WOT conditions, all the adjustments affected by the Long term adaption are applied over-top of the WOT tables. If resetting the PCM eliminates the long term adjustments then the WOT program is also cleared of these adjustments.

That being said,
Clearing the PCM still does not mean that you will gain anything. You could actually loose some power because the PCM has not accounted for the conditions that the engine is running in. (altitude, temperature, gas type)

That's kinda what I just said...

[elcobra44]

Thanks for the quick answers guys!

[maneval69]

That's kinda what I just said...
Just yanking your chain.:whistle:

Anyway I can't track A/F with the SC data logging but here is a before and after PCM reset. (timing and knock sensor). Looks like I lost 2 degrees of timing at peak advance.
So with my car resetting the PCM only hurts. I still can not tell any difference in throttle responce before and after.

http://home.nc.rr.com/maneval69/after%20PCM%20reset.jpg
http://home.nc.rr.com/maneval69/stock_tune_185.jpg