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Can someone look at these LTFT's..

This is a discussion on Can someone look at these LTFT's.. within the Computer & Tuning forums, part of the LSx Technical Help Section category; Johan from diablosport sent me a custom 91 tune for my 5.3 silverado...the fuel trims needed to be adjusted so ...

  1. #1
    Senior Member SeVeReDiStOrTiOn's Avatar
    Join Date
    Aug 2005
    Roseville, CA

    05 Wrangler
    00 Z28 sold :-(

    Can someone look at these LTFT's..

    Johan from diablosport sent me a custom 91 tune for my 5.3 silverado...the fuel trims needed to be adjusted so if you guys can give your opinion that would be great.

    I was getting +7.8 LTFT's going 60mph...I adjusted the injector slope(I think that's the flow rate) to -6% and now it's around +.78 which i'm happy about. But the idle is around -6.8 to this ok for idle? Before i changed the slope I was getting LTFT's of about +1 at idle.

    I also moved the power enrichment to +6% because at WOT I was getting +6 LTFT' the LTFT's are at 0% and the o2's are around 890-910mv. The problem is i'm still getting knock retard at WOT...even after retarding the spark 7%. Should I keep pulling spark until the knock goes away? If the A/F ratio is decently close what else could be causing it to knock? I run 91 octane because that's all we have here in cali.

  2. #2
    Join Date
    Jul 2006
    Glen Carbon, IL

    2000 Camaro SS

    Buy or find someone to borrow a wideband from. I wouldn't trust the narrowband O2's. How much total timing are you running and how much KR are you seeing?

  3. #3
    Join Date
    Oct 2005
    Hi--a couple things---If your LTFT's are a +6 at WOT--that is not where the +6 is comomg from----The computer locks the last LTFT ( if positive) at the rpm point just before going to WOT----Example----If you punch it at 2500 RPM's the LTFT's at 2500 is what the comp will lock on when going to WOT.However if the LTFT's are a negative # just before going to WOT--then the comp will lock on "0"---You need to get rid of the positive ltft's before WOT in order to get did of the WOT LTFT's-----That's why they always say to try to make them 0 or slightly negative --so they will always lock on 0. If you try to correct the ltft's at WOT you will always be chasing your tail because that is not where the +6 is coming from--You need to log the LTFT and see exactly where it is coming from before WOT.Actually i prefer to use the MAF scaler to make these fine adjustments rather than the IFR table--You'll find the IFR changes take a lot of learing to stable out--The MAF changes happen immediately--You just need to log the MAF frquency vs MAP table and change it exactly where its coming from....Typically idle MAF freq is between 2400 and 2700 HZ.

    Once you get rid of all the PT ltft adjustments then you can start on the timing---I don't know what kind of programmer you have but it's best to make adjustments in actual degrees so you know exactly what you've added or subtracted------7% means what ???? you really don't know---Log the timing at a WOT run and see how many actual degress there was at WOT and how many degrees of KR and how many degrees were commanded---a good starting point would be 20-21* WOT with stk combination.
    Last edited by tblu92; 04-06-2007 at 06:21 PM.

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