Fuel Trim Parameters

[McSoloNick]

How do you read LTFT1 and LTFT2 so I can get the best fuel mileage? I’m ready to adjust my Spark Advance and Spark Retard but I can’t get my fuel trims in sync!

[06MonteSS]

fuel trims will always fluctuate, they won't always stay the same.. and bank 1 / bank 2 won't necessarily read the exact same either.. they can be a couple percent different from each other...

as far as what they should be reading, it all depends on your intake air temp, amount of airflow through the MAF sensor, etc..

[McSoloNick]

what does - ltft and +ltft mean exactly because im running high negatives right now? im thinking its lean?

[06MonteSS]

negative fuel trims means you are running rich, and it's subtracting that percentage of fuel to get the AFR back to stoich...

positive fuel trims means you are running lean, and it's adding that percentage of fuel to get the AFR back to stoich...

[McSoloNick]

Alright thanks Monte I have a better understanding and I can adjust them now and not run so rich! The best LTFT range to stay inside for best gas mileage would be close to 0 as possible right? And what about spark advance and retard what does retarding the spark or advancing actually do to your throttle response?

[06MonteSS]

again man, ltft's will always fluctuate.. they won't stay the same.. they're not supposed to.. all depends on intake air temp, rpm's, engine load, etc.. as previously mentioned.. if intake air temps are cold, they should be on the positive side.. if intake air temps are hot, they should be on the negative side.. supposed to be. depends on a lot of factors.. ideally, you want them to be between -5 and +5.... but again, depends on different factors...

and I wouldn't touch the timing/spark advance without doing data logs and knowing what you're looking at and looking for..

I actually end up having to lower the WOT timing a little from the preset canned tune settings when I do my custom tuning for people, due to knock retard I see in data logs... so I would suggest you just leave the timing/spark advance settings alone.

[McSoloNick]

Running high rich sounds better and is more responsive! However I lose power at wot? Does that mean I need to lean my PE?!

[mikel]

how are you determining that its losing power at WOT?

[McSoloNick]

It will literally die down and like it was flooding but I guess I fixed it for now I have my PE as rich as possible and my Injector slope as high as it will go without dieing at WOT and I’m getting way better gas mileage that way but it increased my engine load 2-3% and idle

[McSoloNick]

Excuse that PE is as lean as it will go not rich*