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Thread: LS7 Startup troubles

  1. #1
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    LS7 Startup troubles

    Hello out there, first time asking for help on the forum
    LS7 new build for road racing. Using an E40 ECM with a tune for the same engine before it was pulled out and rebuilt. Made some changes to the engine, raised compression, higher lift cam, more duration.
    Couldn't get the car to start. Would fire and die consecutively time after time no matter what I did to the starting or running air flow parameters. After testing a lot of things, I was at wits end and tried venting the intake by unplugging the vacuum hose from the brake booster and the car fired right up, so I'm assuming it was starving for air.

    Just for a quick test I re attached the vacuum hose and drilled 2 - 1/4" holes in the throttle body butterfly and the car starts and runs perfect but I know this is just a band aid. Any thoughts?

    Thanks in advance.

  2. #2
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    Post a log of you trying to start it if you can. Also, post the tune used in the log you post. If no log, at-least post the tune file.

    Also, please post more build and application details. Do not need the complete build sheet but most will need to know some basics at-least.

  3. #3
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    Yes you're right. Should have done that
    Trying to figure out how...

  4. #4
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    Here is the tune that and log.
    This is with the engine running.
    Attached Files Attached Files

  5. #5
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    Also added a tune from the failed startup before I added air

  6. #6
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    DBW throttle body, MAF and ECU are from a 2005 LS2
    Kooks headers to custom exhaust
    OEM intake
    Cam duration at .050 intake 232 exhaust 240 .593 gross lift intake and exhaust 112 LSA
    12:1 compression
    OEM injectors, fuel pump

  7. #7
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    Cubic inches is wrong if its an ls7. Not sure how much that will help but it needs to be changed.

  8. #8
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    A lot of odd settings in that file. I'll attach a file with some changes you can look over and use if you wish. Just things I would try, no guarantees. All changes assume OEM injectors(as noted) for this OS, stock fuel system, and no TB holes. Just an FYI, do not change injector data unless the actual injector or fuel system has been changed.
    Attached Files Attached Files

  9. #9
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    Alright thanks
    Were the injectors off from what OEM would be?
    I swapped throttle bodies to a non-drilled unit and loaded the changes. No start. I do appreciate the help though

  10. #10
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    Compared to a stock file of the same OS, they were not close.

  11. #11
    Tuning Addict blindsquirrel's Avatar
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    If you combine parts from 3 or 4 different engine RPOs and then say 'OEM injectors', that doesn't really clarify anything.

  12. #12
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    Understood

  13. #13
    Tuning Addict blindsquirrel's Avatar
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    OEM LS7 injectors or OEM LS2 (car) injectors or OEM LS2 (truck) injectors? Or something else altogether? Do they have little part numbers written on them anywhere? Maybe?

  14. #14
    Tuning Addict blindsquirrel's Avatar
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    If you ever wondered why people get burned out and stop posting, this right here is why.

    Quote Originally Posted by KHEath View Post
    Understood
    Unbelievable.

  15. #15
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    Quote Originally Posted by blindsquirrel View Post
    If you ever wondered why people get burned out and stop posting, this right here is why.
    Yes, understood.