[darkpuppet]

naz,May 20 2004, 03:51 AM Wrote:guys can you be more specific when you say the PCM 'learns'

do you mean that it adjusts different parameters to try to bring the fuel trim tables back to where it 'expects' them to be or what?

When the PCM 'learns', it starts off with a base fuel table, and then adjusts the fuel trims to get the commanded air/fuel ratio it's looking for.

It also can advance/retard timing based on load, knock detection, or specific event.

Problem is, when you change what the car is seeing going in, it will do it's best to correct the mixture until the O2 sensor is returning the numbers it wants to see to confirm that it is running near stoich.

Not to mention that it could be adjusting the timing on you as well.

Over time, this can be dangerous if anything happened to the little computers tricking the PCM, the tables could go full rich, full lean, or the spark can go waaaaay off and poof.. -1 engine.

The SCT software enables the tuner to turn off adaptive learning to get the base tune and tables right, and then you can adjust just how much the car does learn, and under which conditions. If none of those parameters are changed, and you try to 'fool' the PCM into doing what you want, it will invariable learn out the changes... until you take it beyond what it can learn, then eventually throw a CEL or piston (worst case scenario)...