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Thread: What direction should I go with this tune, my recipes arent going to plan

  1. #1
    Tuner in Training FourG63 97GST's Avatar
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    What direction should I go with this tune, my recipes arent going to plan

    So since my fuel trims was good before I swaps to these 39lb Cobra injectors.
    i'm focusing on my injector control settings to get it back.

    I'm using rwtd post from
    http://www.hptuners.com/forum/showpo...9&postcount=12
    as my baseline an going from there.

    I attached some logs and my current to show my current fuel trim.
    its averaging -10% to -13%
    besides that fuel trim issue, i'm having like a delay in fuel when hit the gas, like say i'm coasting not giving it any throttle, then get back on it. its goes lean to the 16-19afr range for a second, so i feel it fall on its face everytime before it picks back up an go like i told it to.

    I tried removing 25% from my Injector offset table, that did get my fuel trims back to normal 1-3% range, but they hesitation seemed to get worst, so I put old tune back in just because I think I went it in the correctly.

    so what direction should I go with this? is the Hesitation a VE/MAF issue?
    do I have to redo those also? i took 4 days off from messing with this car an I was just about to swap my 28lb back just so I can enjoy the car for a few days before I go at i again, help

    - 02 Z06, LS2, Twin Turbo

  2. #2
    Tuner in Training FourG63 97GST's Avatar
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    This is the tune an log when I modified the injector offset.
    but seemed to make my hesitation worst

    - 02 Z06, LS2, Twin Turbo

  3. #3
    Tuning Addict WS6FirebirdTA00's Avatar
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    transient fueling is your friend when you have transient fueling issues (on and off the gas, large lean or rich spikes)
    Sulski Performance Tuning
    2000 WS6 M6 - LS6 (long block, refreshed top end), 10.8:1 CR, 90 mm ported FAST, Exo-Skel, 227/232 cam, QTP HVMC, EWP, GMMG, 9" w/4.11s
    2018 Sierra SLT 5.3L A8 - Airaid intake tube, GM Borla catback, L86 Intake/Ported TB

  4. #4
    Advanced Tuner 69lt1bird's Avatar
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    If you look further down in that thread, Greg chimes in on post #17. I think I tried RWTD's stuff when I first put my car on the road and it ran like crap. I don't think you can just plug in the Ford numbers and expect them to work. I attached my tune for you to compare. Mine idles good and does not surge and has a good AFR.

    Here is Greg's quote:
    "James (and others), be careful because the offset point is defined differently in the the GM and Ford injector models. They both essentially use units of time (ms), but Ford models it from turn on to exact opening point (low slope intercept) and GM models it from turn on to theoretical opening point based on linear IFR (high slope intercept). The difference can be significant, especially with larger injectors that have idle PW's less than 2.0ms."
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  5. #5
    Tuner in Training FourG63 97GST's Avatar
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    Quote Originally Posted by 69lt1bird View Post
    If you look further down in that thread, Greg chimes in on post #17. I think I tried RWTD's stuff when I first put my car on the road and it ran like crap. I don't think you can just plug in the Ford numbers and expect them to work. I attached my tune for you to compare. Mine idles good and does not surge and has a good AFR.

    Here is Greg's quote:
    "James (and others), be careful because the offset point is defined differently in the the GM and Ford injector models. They both essentially use units of time (ms), but Ford models it from turn on to exact opening point (low slope intercept) and GM models it from turn on to theoretical opening point based on linear IFR (high slope intercept). The difference can be significant, especially with larger injectors that have idle PW's less than 2.0ms."
    thats alot, I tried your injector flow rate and offset table, an it drive alot! better. the hesitation is no longer there when I step on it.
    the fuel trims did go in the opposite direction though. I'm thinking i'll try messing with the offset a lil bit more an see what results I get?

    - 02 Z06, LS2, Twin Turbo