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Thread: Exhaust flames on over run

  1. #1
    Lifetime Member Tre-Cool's Avatar
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    Default Exhaust flames on over run

    What would people recommend to do to get flames coming out the exhaust on overrun.

    I'm not sure if i should go for negative timing or positive timing when the throttle is closed to "ignite" the fuel.

    Anyone got any tips.

  2. #2
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    moderate timing and alot of fuel, but why? your more prone to damage a turbo doing this. imo
    LQ4, Pro-Flo, heads, Stock48 cam'd, twin TO4E 2001 C5 830rwhp/905rwtq
    2001 GMC RCSB pt88/5.3/4l80e/14 bolt 11.34@123.2 best pass so far with a 1,82 60' @ 13lbs boost

  3. #3
    Lifetime Member swingtan's Avatar
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    I would have thought......

    • Disable DFCO
    • Fudge VE to be rich on low MAP pressure
    • Set timing to be very late, possibly slightly negative


    Oh, and I believe the other requirement is to not run CAT's. And a straight through system.

    Simon

  4. #4
    Lifetime Member Tre-Cool's Avatar
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    Quote Originally Posted by swingtan View Post
    I would have thought......

    • Disable DFCO
    • Fudge VE to be rich on low MAP pressure
    • Set timing to be very late, possibly slightly negative


    Oh, and I believe the other requirement is to not run CAT's. And a straight through system.

    Simon
    First 2 tried, i even tried lowering base spark in gear (i.e when letting off the pedal) to negative -8 degrees and still nothing.

    As for cats well they dont exist in my world.

    I've actually found that having dfco on helps get the burble/crackle sound. I remember a few years back on a cruise one night someone had commented on the flames coming out the exhausts and it was running dfco back then.

    While i have been tuning the new motor recently i have obviously had it off for the auto ve process.

    So have been curious since then on how or what makes it happen.

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