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Thread: 1998 Chevy c2500 Vortec 5.7l 350

  1. #21
    Tuner in Training
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    here is a log with your new table. is this what its supposed to look like? its saying im needing to add fuel where my wideband is showing im at 9.5 lambda which from what ive gathered i should be closer to 1 lambda.

    1998 chevy log file 4.hpl

  2. #22
    Senior Tuner
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    Yes that is what it should look like.

    the AFR commanded only shows the afr command not lambda. I made a math to convert it to lambda if thats what you like to look at.
    Yes it looks like you need to add fuel(a small amount). your commanded afr is 12. and your bouncing between 12 and 12.9. this is commanded lambda .82 and jumping actual between .82 and .88.

    AFR and lambda.jpg
    Last edited by murfie; 12-13-2020 at 05:48 PM.

  3. #23
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    You don't want to introduce MAF waviness that comes from copying and pasting error from a graph.

    MAF wave.PNG

    you can see nearly the whole MAF is lean, so I would just multiply the whole thing by 1.06 and move it closer to the target, before targeting sections of the curve.

  4. #24
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    cool thanks!!greatly appreciate the help. ill post up a log after i rinse and repeat a few times.

  5. #25
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    so i have the maf looking good + or - 2%. im having a issue trying to tune the ve tables. from what i gather the secondary table is used when the maf is failed (i unpluged the maf just to be sure its not messing with me). it starts and my wideband shows a little rich then jumps a little leaner than stoichiometric. i can add 10% more fuel with no change other than the initial start up. im not sure what i need to turn off and cant find much other than disabling long term fuel trim and that did nothing. any input would be awesome!
    Attached Files Attached Files

  6. #26
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    any advice on good tuning books and something that helps navigate the scanner? i just ordered the lesota efi gm book.

  7. #27
    Tuner in Training
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    You still have you LTFT and STFT on. Max on the ECTs on LTFT under Fuel->Oxygen sensors. Disable STFTs under Fuel->Open/Closed Loop and try again.

    I've read a few tuner books. They didn't help. Goat Rope Garage on Youtube is pretty the best tuning advice I've found and has reassured many subject I've read on forums over the years.

  8. #28
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    ok cool thanks.