Help with LTFTs

[toydriver00]

I logged my 07 Silverado today, and I got an average of +2.55 LTFT. The directions say -2 to +2 is okay. How do I adjust the .55 out? Would I use
-1.55?

Thanks

Sean

[06MonteSS]

no, can't do decimals... whole numbers only... I would bring that down closer to 0 or slightly negative though..

adjust the injector slope to -2% or -3%...

drive for about 20-30 miles to let the adjustment settle in, then log it again and see where your average LTFT's are at...

[toydriver00]

I am already running pretty rich. If I change the LTFTs more negative, I am feeding more fuel right???

[dbarden]

No, I believe your a little lean and need to richen it up a small tad.......
(-)LTFT=richer
(+)LTFT=Leaner

Dan

[toydriver00]

So when I change it I will be running more rich than I already am.

[jsk06c6]

No, I believe what happens is the computer then will not need to add any fuel to compensate for the slope being lean. Possibly making it less likely the computer will add too much gas and running rich at cruise. Not sure how this applies to WOT.

Monte?

[dbarden]

I think from my factory manual readings, if I have this right, at WOT you enter a seperate full on tilt mode seperate from the part throttle cruising mode. I am no expert, but I believe this to be the case, hense the PE and Spark Timing adjustments come into play. Still learnining too so don't shoot me if I am wrong. Monty and mike are the ones to be asking though, they seem to know thier stuff.
Dan

[06MonteSS]

at WOT, there is a separate Power Enrichment (PE) table that the computer uses for fueling...

ltft's are only used at normal cruise/part throttle..

UNLESS...

your ltft's are positive at WOT, then it ADDS that amount of fuel on top of the PE fueling setting/amount.

if you're seeing positive ltft's, then you are lean and the computer is adding fuel... hence adjusting the slope negative to add more fuel and get the ltft's down to 0 or slightly negative.

[toydriver00]

I adjusted LTFTs and the truck started making a really loud clack when it went in between V4 and V8 mode. I took the tune out and I have just given up on it for now.