WHAT THE _ _ _ _ ?

[mhslot12]

OK HERE'S A REAL STUID QUESTION ??? WHAT DO ALL THESE ABBERVEATION'S STAND FOR . SO I KNOW WHAT YOUR TALKING ABOUT

LTFT / STFT / PE / VE / STOICH / ECT. IS THERE A GOSSARY

THANKS A NEWBIE

[Screamn03]

LTFT=Long Term Fuel Trims
STFT=Short Term Fuel Trims
VE=Volumetric Efficency
PE=Power Enrichment
STOICH=the best air-fuel ratio for a certain fuel to burn, gasoline is right around 14.7:1 (14.7 parts air to 1 part fuel)
SD=Speed Density
MAF=Mass Air Flow

That's all I can think of off the top of my head right now.

Anyone got any links?

-Mike

[ozorowsky]

Click click:



It is under newbie first sticky way at bottom of forum main.

[mhslot12]

THANKS GUYS FOR YOUR HELP !

BUT ??? WHAT DO LTFT , STFT DO ... WHAT IS THERE FUNCTION ?

THE REST I THINK I HAVE A GRASP OF ...

[Screamn03]

Long Term Fuel Trims is a correction that the computer applies to it's fuel calculation in Closed Loop to correct for variences cause by many things, usually an incorrect aiflow reading (from your MAF sensor or VE table that is referenced by the MAP sensor). Its purpose from the factory is the allow the computer to 'adjust' to it's environment/operating conditions. It can also be a very good tuning tool for closed loop driveability, trying to get them as close to zero as possible. Usually you'll want them slightly negative-reason being if they are positive the computer will add additional fuel WOT which will give you inconsistant AFRs.

Short terms affect the Long Terms although I forget how. Chris, Ken, or Keith posted how it works a while back and I'll see if I can find it. Me personaly, I usually don't pay any attention to them, others will differ. For all I know I'm doing it wrong.

Another Note:

The more they are positive the more fuel that is being added from it's base calculation. This doesn't mean the engine is actually running lean, it means the computer had to correct X amount to run at it's Stoich AFR. It does mean the calibration in the computer is leaner than what the motor wants though.

The more they are negative the less fuel that is being added from it's base calculation. This doesn't mean the motor is actually running rich, it means the computer had to correct X amount to run at it's Stoich AFR. It does mean the calibration in the computer is richer than what the motor wants though.

If you exceed 25 either way the computer gives up and sets a SES light (check engine light).

[Windy_City]

BTW (by the way), WTF would be the proper acronym for your thread title. ;D

[Magic_Chicken]

BTW (by the way), WTF would be the proper acronym for your thread title. ;D

lol

[pknowles]

Another Note:

The more they are positive the more fuel that is being added from it's base calculation. This doesn't mean the engine is actually running lean, it means the computer had to correct X amount to run at it's Stoich AFR. It does mean the calibration in the computer is leaner than what the motor wants though.

The more they are negative the less fuel that is being added from it's base calculation. This doesn't mean the motor is actually running rich, it means the computer had to correct X amount to run at it's Stoich AFR. It does mean the calibration in the computer is richer than what the motor wants though.

If you exceed 25 either way the computer gives up and sets a SES light (check engine light).

So if the ECU is making corrections to the table than what do you gain by altering the table if the ECU is giving it the correct amount of fuel based on what the O2 sensor is saying. If the table is too high or too low and the ECU corrects for it whats the difference of tuning the VE table so your LTFT's are around 0; the ECU will give it the correct amount of fuel based on the O2 right?