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Thread: 12200411 Timing Advance Impass Reached

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    12200411 Timing Advance Impass Reached

    So I was tweaking on the timing tables on my Express with the L31 and noticed that no matter what, it will not run over 34.5* advance. I looked High/Low octane/MBT timing tables and all applicable retard tables and see no reason it should not reach the 42* I have commanded. My guess is that it is an undefined constant not in HP Tuners software. Anyone have luck getting over 34.5* of timing at cruise out of an Express L31 based tune? I was tuning a 4.8 truck the other night and it was running 52-56* of timing STOCK in places going down the highway and from prior experience my other vortec liked 42-46* of timing at cruising speeds. The tight LSA cam I am running has alot of self EGR at low loads and engine speeds and likes the timing. For reference we are talking about the 2,000-3,500 rpm range between 30 and 50 kpa.
    Last edited by Fast355; 09-17-2013 at 04:08 PM.

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    Stock 2001 5.7L 1 ton van

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    With the L31 Vortec your kind of stuck with limitations of distributor at 45* Which is not an issue with 4.8,5.3 COP systems.

    Why you can only get 34.5 in that are looks to be a "Mean Best Timing Spark Advance" Setting?

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
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    Quote Originally Posted by EagleMark View Post
    With the L31 Vortec your kind of stuck with limitations of distributor at 45* Which is not an issue with 4.8,5.3 COP systems.

    Why you can only get 34.5 in that are looks to be a "Mean Best Timing Spark Advance" Setting?
    Values are set at 45 in that area on that table, 45 in the High and Low octane tables. IAT/CTS compensations are -2 and there is zero active knock retard and I always disable burst knock.

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    Quote Originally Posted by Caleditor View Post
    Stock 2001 5.7L 1 ton van
    Thanks for the graphic. I am running th 2002 operating system with a 1500 calibration and I am thinking it may be different.
    Last edited by Fast355; 09-17-2013 at 06:45 PM.

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    Here are the values and ranges I am operating in cruising on flat land.
    Attached Images Attached Images

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    02 are the same

    I remember something Ed Wright posted about timing limits on 4.3L.

    I can tell you that the MBT table has nothing to do with it. I think the OS has another setting for HVS system

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    Quote Originally Posted by Caleditor View Post
    02 are the same

    I remember something Ed Wright posted about timing limits on 4.3L.

    I can tell you that the MBT table has nothing to do with it. I think the OS has another setting for HVS system
    Never heard of HVS before. Its also definately a 5.7 calibration. The 4.3 can take more advance because the spacing is wider.

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    high voltage switch (HVS)

    The type of ignition system


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    Quote Originally Posted by Caleditor View Post
    high voltage switch (HVS)

    The type of ignition system
    Oh that makes sense, just never heard it refered to as that is all.

  11. #11
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    I noticed after emailing HP Tuners about this the other day that the constant had been added to the timing advance tab for maximum advance. It was set at 45 so I bumped it to 55 and now cruise at the 42 of timing I have commanded in low load areas. Running much better now.

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