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

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  1. #1

    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.
    07101518.zip Dan Croteau modified 7.10.zip
    Last edited by LS1Z3M; 07-11-2019 at 08:24 AM.

  2. #2
    Join Date
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    Connecticut
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    http://forums.holley.com/showthread....ents-Read-This (Initial Checks & Adjustments - Read Steps #1-#6!)
    http://forums.holley.com/showthread....2523#post62523 (Holley EFI Tuning Tips & Information)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  3. #3

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    I went through all of the above & more multiple times. I've been working on this for over a month now and have read all recommended readings & checked everything numerous times.
    Last edited by LS1Z3M; 07-11-2019 at 08:27 AM.

  4. #4
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    How much tailpipe do you have after the WBO2 sensor? I'd change your MAP scale to better suite your needs. A lot of wasted space there. Don't use 0 in your MAP scale. Look at your Fuel Table in VE form and you'll see why.

  5. #5
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    Yes, a lot of wasted MAP kPa resolution: http://forums.holley.com/showthread....4365#post44365 (MAP kPa & RPM Axis Configuration/Tuning Information)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  6. #6

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    Quote Originally Posted by 81 TransAm View Post
    How much tail pipe do you have after the WBO2 sensor? I would change your map scale to better suite your needs. A lot of wasted space there. Don't use 0 in your map scale. Look at your Fuel map in VE form and you will see why.
    I did smoothing in VE and noticed that, but could not figure out how to eliminate the "O" axis? Here's a sketch of the exhaust system:
    Click image for larger version. 

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  7. #7
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    Quote Originally Posted by LS1Z3M View Post
    I did smoothing in VE and noticed that, but could not figure out how to eliminate the "O" axis?
    See link in post #5.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

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