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Thread: Help with AFR swings during throttle transitions LS1 in track car - causing concern.

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    Default Help with AFR swings during throttle transitions LS1 in track car - causing concern.

    The engine made 505 HP & 460 ft/lb TQ on the engine dyno and is:
    Stock LS1, 346 CI
    LS6 Intake
    Comp Cam
    Gross Lift .598"/.610"
    Duration @ .050" 231°/277°
    LSA 114°
    Timing INT: 6° BTDC (open) 46° ABDC (close)
    Timing EXH: 57° BBDC (open) 1° ATDC (close)
    Upgraded valvetrain

    It has been swapped into a BMW Z3 used strictly for road course racing on track never driven on the street. The car is light at 2800 lbs. The engine builder tuned the engine on the dyno and after installing into the car it has been further tuned track side. After fixing a problem with air leaking into the exhaust upstream of the WBO2 sensor due to slip on collectors by welding them sealed the car has been running well.

    The one issue that has been constant is that the AFR readings swing rich & lean during throttle transitions. This happens at any RPM/load and is a problem since in this application throttle transitions occur frequently. The engine builder/tuner and I have tried everything to rectify the problem. Most recently I've added injector phasing according to the procedure described elsewhere in the forum and extensive smoothing of the fuel maps using the VE Conversion. I've also played around with other controls including limiting learn at TPS < 20%. But nothing seems to have any impact on the issue.

    Attached is a very short datalog that illustrates the problem and my GF. At WOT and steady state throttle the AFRs are stable and the engine idles fine. Is this something I should be concerned about? If so, any suggestions on what my fix this problem would be greatly appreciated. Dan Croteau modified
    Last edited by LS1Z3M; 07-11-2019 at 08:24 AM.

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