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Thread: Turbo 5.3 False Knock

  1. #1
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    Default Turbo 5.3 False Knock

    Hello All!
    I am still a bit of a Noob when it comes to the programming aspect of performance, so I totally need some help from someone with more knowledge. I am posting this in the forced induction and the transmission section for two different issues.

    To start, this is a turbo (S366) third gen 5.3 with a GT2-3 cam and 2000 LS1B w/ COS 5. Its in a heavy 4x4 with a fresh SRTA 4L80E 2K stall and 3.73's

    I really think this cam is working against me, as I have nothing off the line, but the real question is where is my knock retard coming from? I hear no audible knock, and sometimes KR will appear without much throttle change, or will appear one time and not the other. I have 2 new resonant style sensors in the valley. I don't know if the center frequency is correct, its stock, so is the sensitivity. Should it be cylinder or engine mode? Power and mileage are down, and its just not as fun as a turbo should be! I have some trans tuning issues too, like shift points, but am approaching things one step at a time.

    Thank you for looking!
    Attached Files Attached Files

  2. #2
    Joe (Moderator) joecar's Avatar
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    I see some sawtooth patterns on the KR waveform, it looks like it may be real knock (even of you can't hear it)

    If your VE/MAF tables are correct, then your commanded EQR (GM.EQIVRATIO) is too lean for boost...

    generally, when MAP reaches 90-100 kPa you want EQR to be reach 1.175, and for boost you want EQR to reach to 1.25 or so.

    Also, as MAP increases into boost, you want to bring SPARKADV down more than what you have.

    Both of these (EQR lean, SPARKADV high) allow knock to occur.

    Is there any way you can get colder air in (IAT shows 81*F)...?

    What octane fuel are you using...?
    Try running 100 octane and observe if KR goes away... if it does not, then you may have mechanical sensitivity issue (KS need tuning, or something's hitting, or cam/lifter noise).



    See my comments in your other thread.

  3. #3
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    Joe, thank you again for the help! I am pretty sure the VE is off, as it goes a bit rich. I made all the adjustments from the trans thread, and I'll log this week. I am so glad there are people on here that are both knowledgeable AND willing to help.

  4. #4
    Joe (Moderator) joecar's Avatar
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    Thanks for the kind words.

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