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Thread: Noticed a lot of knock when SD tuning today and now car is stuck in low octane

  1. 06-24-2008 #1
    Gh0st
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    Noticed a lot of knock when SD tuning today and now car is stuck in low octane

    Was SD tuning my car today for the VE and noticed I had a LOT more knock than usual in my WOT areas(remember high and low octane tables are the same when doin VE tuning, so my car was only commanding 24 timing at WOT).

    I said eh, maybe it's the incredibly high heat today.

    Put my normal tune back in my car and do some runs later tonight when it was much cooled off. TO my dismay, all of my timing is coming from my low octane table...seems I have bad gas considering I was having major knock earlier in the day and now the car wants to run in low octane table.

    Besides bad gas, is there ANY other reason why this would be happening?
    2012 Chevy Cruze A6 1LT RS

    Formerly - 2004 GTO, 2002 Z28, 2007 Colorado, 2008 Silverado
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  2. 06-24-2008 #2
    animuL
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    If your "normal" tune is a MAFless tune then you will always run off the low octane tables. Any time you are in SD mode the low octane tables are used.
    98 Corvette Coupe - Texas-Speed 408ci iron block, PRC 237cc heads, Ed Curtis Cam 239-247-115 .624-.624
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  3. 06-25-2008 #3
    Gh0st
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    Quote Originally Posted by animuL
    If your "normal" tune is a MAFless tune then you will always run off the low octane tables. Any time you are in SD mode the low octane tables are used.
    My normal tune is with a MAF. I flashed back in the same tune I drive with every day.
    2012 Chevy Cruze A6 1LT RS

    Formerly - 2004 GTO, 2002 Z28, 2007 Colorado, 2008 Silverado
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  4. 06-25-2008 #4
    WS6FirebirdTA00
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    plugs, knock sensors, lots of oil in the combustion chamber, and a few others as well.
    Sulski Performance Tuning
    2000 WS6 M6 - LS6 (long block, refreshed top end), 10.8:1 CR, 90 mm ported FAST, Exo-Skel, 227/232 cam, QTP HVMC, EWP, GMMG, 9" w/4.11s
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  5. 06-25-2008 #5
    Gh0st
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    Bah...time to find someone to b uy my car. This is getting frustrating.
    2012 Chevy Cruze A6 1LT RS

    Formerly - 2004 GTO, 2002 Z28, 2007 Colorado, 2008 Silverado
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  6. 06-25-2008 #6
    WS6FirebirdTA00
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    check your knock sensors/harness. My harness went out and it was pulling timing. It took a while to set a code though.
    Sulski Performance Tuning
    2000 WS6 M6 - LS6 (long block, refreshed top end), 10.8:1 CR, 90 mm ported FAST, Exo-Skel, 227/232 cam, QTP HVMC, EWP, GMMG, 9" w/4.11s
    2018 Sierra SLT 5.3L A8 - Airaid intake tube, GM Borla catback, L86 Intake/Ported TB
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  7. 06-25-2008 #7
    Gh0st
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    Quote Originally Posted by WS6FirebirdTA00
    check your knock sensors/harness. My harness went out and it was pulling timing. It took a while to set a code though.
    Will do. I'm also going to fill the rest of my tank with 93 octane from a different gas station. It wouldn't surprise me if they put 87 octane in the 93 tanks here...
    2012 Chevy Cruze A6 1LT RS

    Formerly - 2004 GTO, 2002 Z28, 2007 Colorado, 2008 Silverado
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  8. 06-26-2008 #8
    Gh0st
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    Is there any thing I can reference with Hptuners that can read if the car is in low octane mode due to the gas at all?
    2012 Chevy Cruze A6 1LT RS

    Formerly - 2004 GTO, 2002 Z28, 2007 Colorado, 2008 Silverado
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  9. 06-26-2008 #9
    WS6FirebirdTA00
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    no, you can only use the knock learn factor to see if it is in the low or high octane table.
    Sulski Performance Tuning
    2000 WS6 M6 - LS6 (long block, refreshed top end), 10.8:1 CR, 90 mm ported FAST, Exo-Skel, 227/232 cam, QTP HVMC, EWP, GMMG, 9" w/4.11s
    2018 Sierra SLT 5.3L A8 - Airaid intake tube, GM Borla catback, L86 Intake/Ported TB
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  10. 06-28-2008 #10
    tahoe
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    I Seem to remember that once there has been enough knock to use the timing from the low octane table, you need to fill up your tank before the ECU start using the high oct table again. The reason makes perfectly sense, the gas that made it knock cant be gone before the tank meter ragister a fill up.

    //
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