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Thread: HELP! can't keep off the rev-limit/fuel-cut

  1. #21
    Lifetime Member jfpilla's Avatar
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    I think I know what the other guy is talking about with the vette and unhooking the MAF causing the power-loss thing, but this isn't the same problem at all. This problem isn't even consistent.

    I'm not talking about the Maf Rationality Test. I've never seen a good explanation, but it is said the 1998 MAF is involved in torque measurements and shifting. But if you had the problem with the MAF hooked up that's not it. Unless you had changed MAF values.
    2003 red vert
    Mods:
    LS7 crate engine, wet sump, 24xx reluctor
    LPE 100mm MAF
    Vararam, cold air intake and bridge
    RPM Level 6/4L60e trans
    3.42 gears
    Yank SS3600
    1-7/8" AR headers
    Z06 exhaust
    470rwhp 437rwtq
    1/8th mi-1.526-60'-6.862-1/8th-@100.74mph

  2. #22
    Lifetime Member Scoota's Avatar
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    Ahh, thats right, the 98's don't have CO's as yet, It's the Aussie in me to have thought otherwise. Sorry guy's.

    Cheers Scotty.
    It's a lot easier to ask for forgiveness than it is to ask for permission.



  3. #23
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    Rev-limiter parameters:
    ETC Rev Limit = enable/disable
    Fuel Cut-Off in P/N = 7800
    Fuel re-enable in P/N = 7700
    Engine overspeed time allowed = 3.0 seconds
    VSS failed RPM upper limit = 7800
    VSS failed RPM lower limit = 7700

    Fuel Cut-Off in gears: all set to 7800 C/O and 7700 re-enable

    Abuse management parameters:
    A/M in gear upper RPM threshold = 8000
    A/M in gear lower RPM threshold = 1500
    A/M P/N upper threshold = 7300
    A/M P/N lower threshold = 1500
    A/M time = 0 seconds
    A/M VSS threshold = disables at 2 MPH

  4. #24
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    Anyone want to take a look at the bin ? I could mail it tonight after work.

    Who's going to be the first to get a CO for a 1998 vette?
    This one sure needs it.

  5. #25
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    TT I am very interested in this thread also as I have the same setup.
    Must go faster.

  6. #26
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    send it along I dont mind.

  7. #27
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    Quote Originally Posted by dbaxter_ss
    send it along I dont mind.
    pm me with your email please.
    .. that is if you meant for me to send the bin.

  8. #28
    EFILive Distributor dfe1's Avatar
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    It may be that you're chasing the wrong thing. You don't list any details about the engine, so this may be way off base, but you may be experiencing valve float/lifter pump up. When you hit a rev limit caused by a fuel cut, it's a very distinct "hard" limit that shuts the engine off, until engine speed drops to the re-enable rpm. On the other hand, if the rev limit is caused by the valve train or an ignition or fuel system problem, the engine just kind of "hangs around" near the rpm "limit". Try setting your limiter to 6200 rpm and the re-enable to 6000 rpm. That will put the limit below the speed at which you're having the problem. Then test it and log the drive. You should feel rpm go to 6200, then the engine will die for what seems like an eternity, then come back to life when rpm drops to 6000. If that works, you know the limiter and re-enable control are operating properly. Then raise the limiter to 6500 and the re-enable speed to 6300 and repeat the test. If you don't get the same type of response at fuel cut and re-enable, that pretty well proves the limiter isn't the problem. You might also check the fuel filter. If fuel pressure takes a dive, you can also experience a "soft" rpm limit-- you should be able to see this in the O2 voltage. If it would help, I'd be happy to take a look at your tun and log files.
    DigitalEFI- EFILive US Distributor
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  9. #29
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    No answer yet.
    ttt.

  10. #30
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    Quote Originally Posted by white2001s10
    No answer yet.
    ttt.
    Did you ever figure this out? I have had the same problems for years.
    I have a 97 Vette and have had 3 engines, several gear changes, run CL and OL with MAF. It always seemed worse with lower gears (410 & 373). I always thought it was a nitrous problem, but I now have a LS7 in my car that is N/A.
    I can't raise the shift points any higher than about 6200 to 6300 rpm with out
    having the rev limiter/fuel cut out shut the car down. I could live with this when I was using Nitrous, but would like to rev the LS7 higher.
    I have read about this problem before over the years, but have not got to the bottom of this. I would like to figure it out before I die

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