PCM tuning terms defined

[Tavenner13]

i have no idea what this stuff means... help. maybe this can help other who are having a hard time following the custom tune forums. im looking to get a custom tune but i want to try and somewhat understand what is going on and im lost.

crank re-learn? what does it do?

OBD2 or whatever?? what is that?

what all does the PCM do? why are these trucks so mildly tuned from the factory? if torque management is so bad, why dont people remove it 100% instead of only like 40%? can some one sort of give me a PCM tuning 101 crash-course?? i would REALLY appreciate it

[DefEddie]

wtf:i have no idea what this stuff means... help. maybe this can help other who are having a hard time following the custom tune forums. im looking to get a custom tune but i want to try and somewhat understand what is going on and im lost.

Originally Posted by Tavenner13

crank re-learn? what does it do?

The PCM get's reference signals from the CKP(crank sensor) and the CMP(cam sensor) so it know's exactly where everything is in relation to each other. The CKP is a halls effect sensor,meaning a (powered)magnet that is fixed while a spinning wheel rotates. The spinning wheel has notches in it,as they pass by the magnet the voltage fluctuates.The signal fluctuation is what goes back to the PCM as a voltage signal.
The spinning wheel and magnet over time change,wear etc.. The pcm needs the signal to be as accurate as possible(i'll explain why) so it learn's the various changes and issues over time in the wheel and magnet(sensor). That info is stored in the computer in a permanent memory. If you change the cam or crank correlation in any way or change PCM's then it will need to relearn it to do it's job correctly.
The job of the CKP and CMP are too much to get into,but they are vital to proper engine operation.
In regard's to the crank relearn,it uses that information so it know's when the truck is misfiring due to change's in crank rotation and speed.
It is not integral to vehicle functionability for you to have the relearn done,it will drive fine without it. But the PCM might compensate for false misfire's or even report false misfire's. Basically if you don't do it you are handicapping an important part of the engines natural defense's against thing's like bad gas,fouled plugs,bad injector's etc...

Originally Posted by Tavenner13

:OBD2 or whatever?? what is that?

On Board Diagnostics II
It is basically a way to get everything on one level. The US EPA has mandates that allow you so many emission's,and requires this and that. The OBDII system is what they came up with to monitor it all,in one programming language that everyone can read(actually several languages)It also has built in warning's for emission's malfunctions and errors,and controls the engine for maximum efficency.
That's a VERY general description and not a good one.

what all does the PCM do? why are these trucks so mildly tuned from the factory? if torque management is so bad, why dont people remove it 100% instead of only like 40%? can some one sort of give me a PCM tuning 101 crash-course?? i would REALLY appreciate it

The factory care's about 2 things really, Emissions and Durability.
They DO NOT want EPA fine's,which are no joke.They have to meet the ever increasing standards that the EPA sets forth,so they mainly tune for emission's and fuel mileage(which means better emissions)
Thing's like torque management and such are built in by the manufacturer simply because they don't want to pay warranty claims for abused vehicles. They aren't necassary trying to take away the power so much as they are trying to regulate it so it has the least amount of negative impact.
Tuning for fuel and spark are off simply because no vehicle is exactly the same,yet every vehicle off the factory line get's the same generic tune. The factory no doubt spent alot of time on that tune to maximize performance,driveability and fuel economy while staying within emission's parameters.
Factory engine's are terrible about having bad tolerance's anyway. Most anyone can totally blueprint a stock engine to tighter spec's and pull out 30+hp reusing the stock parts.
The tolerance's and minute difference's are what your tuning for when you tune a stock vehicle and get power.
You could take 2 stock camaros and tune them right off the factory line and 1 might gain 20hp and the other might only gain 5hp,it all depends on the vehicle.
If you truly wanna understand about EFI,then read up on the Ideal Gas Law theory which is what all modern fuel injection is based on and it's the base formula for fuel tuning.

People don't remove ALL TM usually because a 4L60E sucks. It is not a truck transmission and never should have been put in these. Even a built 4l60e can't handle alot of power reliably. If you have mods,and you take out the torque managemnt then it will simply shock the tranny to much on gear engagements.
The 4l60e has thin stamped steel and aluminum components inside,and isn't built for heavy duty. Leaving some TM in will allow the tranny to last longer,since it's still taking out the shock for the shift though it's just not totally killing the performance.
Hope I helped,i'm just an amateur.

[DefEddie]

Here,found this on OBDII
http://www.obdii.com/background.html

[Lchauvin88]

I had removed 75percent torque management in my 02 s10 4.3 4l60e. I know its not the same. I have had the tune in the truck for roughly 10k miles and never had a problem even with 100shot nitrous, and 9psi on a vortec blower. Both of which are sold. Still have the truck though heheh.