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Thread: GM 1.4 E78 PCM 4300 Rev Limit

  1. #1
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    GM 1.4 E78 PCM 4300 Rev Limit

    E78 PCM. Vehicle not moving, NO VSS. WOT produces 4300 RPM Rev limit. What table is 4300 in? How do you change the 4300 limit?
    This particular stand alone set up is 2015 Trax manual in Lotus 7 autocross car. No clutch sensor. No brake sensor. VSS is off tail shaft of T5 transmission.

    TIA

  2. #2
    if you are talking about the limiter is only active at standstill it it most likely your case learn rpm limit

  3. #3
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    If that is adjustable, how do we get at it?

  4. #4
    it's in the Fuel> Cutoff tab

  5. #5
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    Quote Originally Posted by dertobi View Post
    it's in the Fuel> Cutoff tab
    Do you mean "Case Learn"?
    I don't think that is it, but I could be wrong.
    I think it's hidden in a table that we can't see.
    HPT would have to unlock it.
    Last edited by sprinto7; 07-25-2018 at 03:29 PM. Reason: Add n=more info.

  6. #6
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    I'm not familiar with that particular OS but there is probably a fuel cutoff for park and drive(gear) If the PCM doesn't know it's in gear it's obviously going to use the park table.

    The PCM does use the park fuel cutoff to do the case learn.

  7. #7
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    The rev limit I
    'm speaking of is in a hidden file.

  8. #8
    Senior Tuner cobaltssoverbooster's Avatar
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    some things i would try...
    not knowing your tps values during this event but have you set the vss misc cutoff to 100%?
    have you tried setting predicted toque control method to disabled?

    the other table i have thoughts about is the acceleration based thresholds. if the stock value is .3 and in the table you have 875 rpm at 4600 then when you take into consideration the filer coefficient that 875 rpm variance turns into a 262 rpm variance which gives an rpm value of 4345 rpm. i would give raising the filter coefficient a shot. say raise it a significant amount to check if its a limiting factor. ex: values of .75 or 1.0
    2000 Ford Mustang - Top Sportsman

  9. #9
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    Quote Originally Posted by sprinto7 View Post
    The rev limit I
    'm speaking of is in a hidden file.
    You should have a good talk with the people that sorted this out, they might help