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Thread: LS1 Conversion Possible Fuel Starvation (After 10-15mins of driving)

  1. #1
    Tuner in Training
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    Jun 2021
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    LS1 Conversion Possible Fuel Starvation (After 10-15mins of driving)

    Hello all,.
    I have an M6 5.7 LS1 in an Australian car (late 70's). The engine is standard internally with new plugs, leads and injectors. The intake is the factory intake pipe, MAF and aftermarket pod filter.
    The fuel system is a Aeromotive in tank Phantom setup running a Covette filter regulator. A mechanical gauge on the fuel rail shows a steady 55ish psi at idle/revving. The fuel tank has breathers attached and is vented through a vapour seperator (1 x breather from the Aeroflow setup, 2 x from the original tank)
    The tune in the car hasnt had much done to it (idle speeds, fan speeds, a little VE table adjustment etc)

    The issue im having is that the car seems to be running out of fuel after running for 10-15minutes. It has repeated this issue 3 out of the last 5 short test drives performed. A re-routing of the fuel tank breathers took place before the last issue to ensure the best possible chance for tank breathing is taking place.

    Symptoms: Car runs fine, idles fine, drives around fine for a good 10 mins or so. Then it feels like it has run out of fuel (struggles to keep running, surges, needs heavy throttle input etc) Pulling over and stopping/re-starting seems to clear the issue. The log file attached shows it idling fine after struggling for just over 1 minute (12.5 mins into the log)
    The 02 sensors show an extreme lean condition when the issue occurs (02 sensor voltages < 60mV)

    My question is: Is there something in the log or tune file that I am missing? Does the data suggest a tune/ECU issue or should i be looking at a mechanical issue?

    Thanks in advance
    Attached Files Attached Files

  2. #2
    Tuner in Training
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    Jun 2021
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    Bump!

    So this issue has almost beaten me.
    Changes introduced to try and recitfy:
    - Remove/re-install fuel tank and pump to see if there was a clear issue with return/pickup lines (No issues found)
    - Measured feed and return flows (No issues found)
    - Removed Wix filter/reg and replaced with Aeromotive adjustable reg and dedicated return line. Base fuel pressure set to 58psi
    - Added in a fuel pressure transducer so I can log fuel pressure (Fuel pressure moves approx 1psi when driving)

    The issue is still there! Im confident I can say its not a fuel supply or pressure issue.
    Battery voltage also looks good also when running (Constant 14volts)

    This issue is beating me! In the logs the issue presents as teh cylinder airmas dropping and the MAF and Dynamic air flows diverging (Dynamic air flow drops away from the MAF airflow) This is immediately followed by the 02 voltages going to almost 0 (60mV). Giving the car more throttle is the only thing that keeps it running.

    Im looking at the cylinder airmass number dropping immediately (cruising at 0.28-0.29g then dropping immediatly to 0.11g) and the dynamic air flow immediate drop as the "start" issue when it arises. I just cant work out what would cause this dynamic airflow sharp drop.

  3. #3
    Tuner in Training
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    Jun 2021
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    Cheers for the replies!
    Turns out running it in SD mode sorted it out. The MAF data looks ok, but for what ever reason it is causing a big drama.
    Updated the VE table using the fuel trims to get it in the window.

    I have no idea why the dynamic air calc was getting so messed up for random periods of time, but running in SD seems to fix it.

  4. #4
    Senior Tuner
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    Quote Originally Posted by BENN0 View Post
    Cheers for the replies!
    Turns out running it in SD mode sorted it out. The MAF data looks ok, but for what ever reason it is causing a big drama.
    Updated the VE table using the fuel trims to get it in the window.

    I have no idea why the dynamic air calc was getting so messed up for random periods of time, but running in SD seems to fix it.
    Thanks for the update. It's odd that it didn't show up in the MAF data, but at least you found a resolution.

  5. #5
    Tuner in Training
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    Jun 2021
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    Im assuming there is a MAF scaling issue.
    Once i get the SD tune spot on, then i'll go back and try and tune the MAF and see if it helps. Not sure why the scaling would be out though? Brand new MAF and stock tune.