how low til your fuel trims settle after reset?

any idea? I heard that the older year model a vehicle, it is generally assumed it takes longer for the fuel trims to settle (older softward, older/slower processing speeds, etc.)

Im pretty sure mine dont settle that quick, cause STFT are still logging. Does that mean that LTFT aren't settled yet? Im confused on this aspect still.

If you reset the fuel trims after rewrite, it only takes 20 mins or so. If you don't, it could take a week or two from what I've heard. You can reset the trims by pulling the PCM fuse or battery for a couple of hours, but PT has a "reset fuel trims" option even for partial rewrite.

The way I understand LTFT & STFT (I know, it's confusing) is that STFT is the immediate fuel correction that your PCM is commanding. LTFT on the other hand, is "learned" fuel correction based on many STFT results over time. LTFT is the PCM's best guess based on past circumstance. That's the way I think of it anyway. Smaller adjustments create faster LTFT changes, larger ones may take more time to learn, that's my theory.

well, hopefully that means my LTFT are gonna change. They were a litlte high +1-2 but the STFT were -1-2. I'll just have to scan again.

have you done the VE tune on your car, or should I say have you finished the VE tune yet?

I haven't tried it yet. driving around with a maf sensor off for a few days didnt sound appealing.

so if you drive a bunch of ways all the time. ie; race one minute then cruise for 15mins the LTFT will take a longer time to "level out"?

i dont see + or - 1 or 2 as high, from what i have gathered anything from -5 to +5 is acceptable and it means the long term is doing its job to adjust the fuel.

quote: "so if you drive a bunch of ways all the time. ie; race one minute then cruise for 15mins the LTFT will take a longer time to "level out"?"

I believe this is true. After doing a few WOT runs, it seemed my LTFT when up for a while, but settled eventually. My car isn't fully tuned though, so it might be different when you've got everything set right.

I have not done the VE tune.

Mr.Riviera wrote:

so if you drive a bunch of ways all the time. ie; race one minute then cruise for 15mins the LTFT will take a longer time to "level out"?

i dont see + or - 1 or 2 as high, from what i have gathered anything from -5 to +5 is acceptable and it means the long term is doing its job to adjust the fuel.

the theory is to have them -5 to 0. You want to be rich, if you have to choose between that and lean. A richer conditions is technically safer than a lean one.

if they are zero or rich to begin with and you go WOT, your fueling is starting from a rich conditions which is desired since WOT commands tons of fuel.