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Thread: Knock Sensor Multiplier

  1. #1
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    Knock Sensor Multiplier

    Good evening. I have a question about knock sensor multiplier settings. I'm seeing (and hearing) a bit of KR. In my logs i'm seeing 3.5 degrees of retard in the 1800rpm and .28 cyl/AM cell. I'm seeing it in lower rpm a little as well. Now my question is the tune i currently have has the sensor multipliers table for all cylinders set to 6.5. Looking at a number of tunes in the repository none has settings that even remotely look like this.

    Why would the tuner set the knock sensors like this?

    Car in question is the pacific slate in my signature.
    Last edited by dave05gtpcg; 02-23-2021 at 10:32 PM.
    2009 G8GT Pacific Slate
    408Ci iron block
    TSP forged crank
    Carillo rods
    Diamond pistons
    GMPP Ported 821 heads
    BTR .685 springs
    TSP F35 stage 4 cam
    Circle D 254mm billet from triple disc 3600 stall
    Tick Ported oil pump
    Kooks 1 7/8' Jet Hot LT
    Solo Mach Shorty No cat
    Rotofab

    2008 G8GT Red
    Fast LSx102 intake
    NW102 TB
    TSP Stage 2 cam
    GMPP ported heads
    Squash dual pump fuel system
    ID850 injectors
    RotoFab 4" intake with LS3 card MAF

  2. #2
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    That's a pretty aggressive setting. If you're hearing it and seeing it in the datalogs, then it's real knock and needs to be addressed.
    Are you running the same type fuel that it was tuned with?

  3. #3
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    Yeah same grade of fuel, different brands though. I've attached the tune, the log I have is too large to attach.

    Both cars in my signature are tuned by same shop, the red one I just realized has 6.9 degrees of KR

    Looks like its time to pull some timing?
    Attached Files Attached Files
    2009 G8GT Pacific Slate
    408Ci iron block
    TSP forged crank
    Carillo rods
    Diamond pistons
    GMPP Ported 821 heads
    BTR .685 springs
    TSP F35 stage 4 cam
    Circle D 254mm billet from triple disc 3600 stall
    Tick Ported oil pump
    Kooks 1 7/8' Jet Hot LT
    Solo Mach Shorty No cat
    Rotofab

    2008 G8GT Red
    Fast LSx102 intake
    NW102 TB
    TSP Stage 2 cam
    GMPP ported heads
    Squash dual pump fuel system
    ID850 injectors
    RotoFab 4" intake with LS3 card MAF

  4. #4
    Tuner ttz06vette's Avatar
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    Quote Originally Posted by dave05gtpcg View Post
    Yeah same grade of fuel, different brands though. I've attached the tune, the log I have is too large to attach.

    Both cars in my signature are tuned by same shop, the red one I just realized has 6.9 degrees of KR

    Looks like its time to pull some timing?
    ...or add meth

  5. #5
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    Maybe in the future ttz06vette, plan is to force feed it at some point as well.

  6. #6
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    Should I lower the multipliers for each cylinder to say around 3.5-4 and log KR to see how much it?s experiencing with it set more sensitive?

    Wonder if this is why my HP numbers seem low?

  7. #7
    Senior Tuner 10_SS's Avatar
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    Quote Originally Posted by dave05gtpcg View Post
    Should I lower the multipliers for each cylinder to say around 3.5-4 and log KR to see how much it?s experiencing with it set more sensitive?

    Wonder if this is why my HP numbers seem low?
    Usually tuners reduce that value to make the sensors ignore more knock, so they are able to run more timing. I dont agree with this strategy, but that's what they usually do. Not sure why he increased them, this makes it more sensitive. This is why I tune everything my self. Kinda hard to know if your getting the most power out of the combo without a dyno, but you can generally figure it out by adding timing to the point you start seeing knock unless your running so much E85 you dont see knock, then playing with ARF. MPH at the track is a good indicator of that.

    The problem with having knock retrard, is it pulls more timing than you really need, so by fixing the knock (perhaps by pulling some timing) you will end up making more power. Tuner should know this.
    2010 Camaro LS3 (E38 ECU)
    Whipple 2.9L, 3.875" Pulley, kit injectors, supplied MSD Boost-A-Pump, stock pump
    LG Motorsports 1 7/8" Headers - No Cats, stock mid pipe with JBA Axle Back
    ZL1 Wheels/Tires

  8. #8
    Tuner ttz06vette's Avatar
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    Quote Originally Posted by 10_SS View Post
    Usually tuners reduce that value to make the sensors ignore more knock, so they are able to run more timing. I dont agree with this strategy, but that's what they usually do. Not sure why he increased them, this makes it more sensitive. This is why I tune everything my self. Kinda hard to know if your getting the most power out of the combo without a dyno, but you can generally figure it out by adding timing to the point you start seeing knock unless your running so much E85 you dont see knock, then playing with ARF. MPH at the track is a good indicator of that.

    The problem with having knock retrard, is it pulls more timing than you really need, so by fixing the knock (perhaps by pulling some timing) you will end up making more power. Tuner should know this.
    I thought the Higher this value the more desensitized the sensor will become?

  9. #9
    Senior Tuner 10_SS's Avatar
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    Quote Originally Posted by ttz06vette View Post
    I thought the Higher this value the more desensitized the sensor will become?
    Maybe your right, it says "Multiplies knock sensor threshold", which raises threshold, everything I said still applies. Like I said, they usually desensitize the knock sensors so you can run more timing, and call that optimizing the tune. But if you still have knock, then your losing power, so pull the extra timing back out and you will net more power than running it with knock.
    2010 Camaro LS3 (E38 ECU)
    Whipple 2.9L, 3.875" Pulley, kit injectors, supplied MSD Boost-A-Pump, stock pump
    LG Motorsports 1 7/8" Headers - No Cats, stock mid pipe with JBA Axle Back
    ZL1 Wheels/Tires

  10. #10
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    Awesome thanks for the replies! The way I understand it is the higher the number or multiplier the less sensitive or less likely it is to pickup knock. I think what I?ll do is take the factory G8 GT multiplier tables and add 20% log KR and make adjustments accordingly. I?ll let y?all know my results.

    Again thanks for the responses.

  11. #11
    Tuner ttz06vette's Avatar
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    Yes that is the way it works for me. I actually log Kr by cylinder and increase the thresholds only for the cylinders that are contributing to the overall knock.For example, I have Corsa’s and headers and my cylinder 8 accounts for the majority of the overall knock. Once I pulled a plug and verified it looked no different then the rest, I added 20% to just that cylinder and it brought overall to nears 0. You might want to consider logging each cylinder.

  12. #12
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    Ttz06vette that?s interesting. I?ve never seen it done that way but makes a lot of sense. I?ll definitely give that a shot. Thanks for the tip!