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Thread: trouble with warm starts ls7 need tuning advice

  1. #1

    trouble with warm starts ls7 need tuning advice

    2007 C6 Z06 Twin Turbo, big cam. the high torque aftermarket starter, and battery have no issues, they can crank the car without problems when its hot, there's no slow crank or anything like that. If i pedal it a few times, eventually it will fire and then has no issues. Hence the car can crank without issue, and once it sees the gas and air mix it wants it fires right up.

    I have noticed that maf is lowest in the warm starts log, and iat is highest. the turbos have a direct filter attached and they are in the engine bay. I have tried lowering cranking spark, lowering cranking fa, and raising the startup airflow, and there seems to be no changes with any of these adjustments.

    my afr commanded is 1.25 during warm crank, around 1 during semi warm and .25 during cold crank, im thinking not enough gas being commanded?

    I have 3 recordings, cold, almost warm, and completely warmed up. the car only long cranks in completely warmed up. I am open to suggestions and advice, thank you in advance for any help with this.

    latest (2).hpt
    long cranking when fully warmed up driving for 20 minutes.hpl
    cold start no issues immediate fire.hpl
    semi warmed up started just fine.hpl
    Last edited by Gpargament; 05-26-2023 at 06:57 PM.

  2. #2
    Tuning Addict
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    What's actual rail pressure when you're cranking it hot? Almost looks like pressure lock or lack there of especially when you can keep cranking and giving it that much air without it even trying to fire. Injector pw's are very low during cranking - if fuel pressure checks out good with no bleed off and not too high then try increasing crank fuel especially where you have .8's.
    Last edited by GHuggins; 05-26-2023 at 07:38 PM.
    2010 Vette Stock Bottom LS3 - LS2 APS Twin Turbo Kit, Trick Flow Heads and Custom Cam - 12psi - 714rwhp and 820rwtq / 100hp Nitrous Shot starting at 3000 rpms - 948rwhp and 1044rwtq still on 93
    2011 Vette Cam Only Internal Mod in stock LS3 -- YSI @ 18psi - 811rwhp on 93 / 926rwhp on E60 & 1008rwhp with a 50 shot of nitrous all through a 6L80

    ~Greg Huggins~
    Remote Tuning Available at gh[email protected]
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  3. #3
    Thank you very much, I will double check, I had a mechanical gauge on the rail recently and it read 58 after being primed, but I've never watched it while cranking. I appreciate the help