Does the computer really learn?

[ShadowBolt]

When I was looking at CMC17 for the first time I ask Eric what the switch on the fender was for. He said it was a master switch but that I should not turn it off because the computer learns how the car is driven and will run better if left on. Well I turn it off (just like in my motorhome) to make sure the battery does not go down. Is this wrong? When Wayne rode with me at MSRC on 12-29-07 he thought the car was a little down on power (we will find out today at the dyno). Could I have caused this by disconnecting the computer and losing what was "learned"?
I doubt it myself but I would like to know for sure.

JJ

[marshall_mosty]

Jerry,
My computer goes dead every time I turn off the master... hasn't seemed to hurt it any. However, it does hunt for idle while cold. Once it warms up, all systems are go.

However, I have also heard/read that the computers do "learn" and "remember" what some of the sensors are reading and how fast they respond. So... it's probably better to not kill the power each time if you can get away without it.

[GlennCMC70]

long term fuel trends. the computer will start to correct the air fuel ratio as the car is driven. this is the learned part. it keeps this info and its new adjusted state in the memory. when you kill the power to the PCM, it goes back to default and has to start over.
my 98 LS1 car for example took a few days for the LTFT's to stablize. once it hits 25% (the max the computer can compensate for LS1 bases cars) you will have to tune the computer to get the right mixture.

as for killing the battery? not if its wired correctly. the computer has 2 types of 12v requirements - PCM Batt and PCM Ign. the batt one is just that, connected to the battery at all times. the ing one only needs power to let the car run. as long as you only have the PCM Batt drawing power w/ the master switch on and the car off, you will not kill the battery in the time between races or from one season to the other.

i leave my master switch on 24/7. i only turn it off to test it, or if i'm working on the electrical system and i want to remove power from everything. i've never killed the battery in my CMC car from leaving the master on. in fact, i've had the same battery for 3.5 years now. no issues. for EFI cars, leave it on. for carb cars, doesnt matter.

[GlennCMC70]

i also contribute the 2005 DQ i recieved for being over on power to this (and another major issue - poor dyno maint). i dyno certed the car w/ no time at all on the PCM. the motor was on a stand for 3+ years and then i dropped it in and dyno'ed it. the car was raced almost a whole season and then re-dyno'ed. once i was DQ'ed i reset master power and saw a drop in the dyno numbers. this could have easily been an increase too. depends if the motor saw any major knock at high temps and stuff.

basically, its a big ass can of worms thats best left un-opened. leave the switch on. if it killes your battery, get the car wired correctly.

[ShadowBolt]

My battery has not gone dead, I was turning the switch off as a back-up. It's really hard on a battery if it does get pulled down to sit there discharged in cold weather. I will leave it on.


Jerry

[Fbody383]

My $0.02

It may vary by manufacturer but my understanding is that it is an OBDII, or post 95 model year function.

With the stricter emissions mandates and emission reporting of the OBDII cars, the learning capability let the engines "learn" to run more towards maximum efficiency - probably under contstant and partial throttle conditions that most cars see regularly.

I've had the same experience as Glenn with my 98 M3. If I take it autocrossing/open track and drive it hard with the traction control off and significant time at full throttle, it really wakes up.

[AI#97]

My $0.02

It may vary by manufacturer but my understanding is that it is an OBDII, or post 95 model year function.

With the stricter emissions mandates and emission reporting of the OBDII cars, the learning capability let the engines "learn" to run more towards maximum efficiency - probably under contstant and partial throttle conditions that most cars see regularly.

I've had the same experience as Glenn with my 98 M3. If I take it autocrossing/open track and drive it hard with the traction control off and significant time at full throttle, it really wakes up.

All more reasons to be sure you do the same thing you do at your annual dyno, and if you get drawn from the hat to dyno.