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Thread: Can't get rid of knock on 1000-2000RPM 0,5-0,9 Load

  1. #1
    Tuner in Training
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    Nov 2021
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    Can't get rid of knock on 1000-2000RPM 0,5-0,9 Load

    Hi.
    1st gen Coyote issue.

    I've been trying to dial in the spark Borderline tables for a few weeks and I am still getting knock in low rpm areas.

    I have a very retarded spark in this areas like 0* to even -10* . These values are a result of many logs with knock, so I was retarding spark piece by piece to reduce knock. But in the logs I can see that the spark is sth around 20-30 degrees. Spark source is Base/MBT. I understand that the final spark is not exactly what I have in the tables, because there are a lot of multipliers (ECT, IAT etc.) but is that possible that such huge difference is caused by multipliers?

    Example:
    spark issue.jpg

    Car is on Mapped Point 3 in 90%, 1500rpm and 61% load. The spark is 24,9* , but depending on borderline table I should have -11 degrees.

    spark MP3 borderline.jpg

    I notice that anytime when the spark source is Base/MBT , the actual spark has always a different value than value in the borderline tables.

    The question is - why the PCM is choosing MBT if Borderline has lower values? What I learned from other threads is that the PCM is taking spark values from either MBT or BKT depending on which one is lower. I have lower values in BKT but the spark source is MBT.

    In such situation does it make sense to do any changes to borderline in these areas? If the knock occurs while the spark source is Base/MBT should I change the MBT tables to eliminate the knock?

    could someone advice me if I am doing sth wrong here and why I am having the spark source base/mbt? Or maybe this knock is a false knock?

    The car is mostly stock - i only have aftermarket cats.

    log and tune attached.

    thanks.
    frank
    Attached Files Attached Files

  2. #2
    Advanced Tuner
    Join Date
    Jun 2020
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    776
    Similar issue turned out to be octane adjust:

    https://forum.hptuners.com/showthrea...se-back-to-BKT

  3. #3
    Tuner in Training
    Join Date
    Nov 2021
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    Hi, Thanks I saw that before, but thought this is impossible that all adders and multipliers could add like 20 and more degrees of spark to the borderline

    Will check it ...

  4. #4
    A shot in the dark here. Is your speedometer working and accurate?

    I was experiencing negative total timing rolling into the throttle in 6th from 2000 rpms. To get my speedo to read actual speed, I had to use incorrect axle ratio (1.8 and I had 3.73s). Once I fixed trans settings in tune, no more issues with negative timing, or whacked load calculations. I can now go WOT in OD at 1500, it it pulls just fine and timing stays BTDC.
    Last edited by JuiceNA; 01-18-2022 at 04:04 PM.

  5. #5
    Tuner in Training
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    Nov 2021
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    25
    No issues with the speedo
    Car is manual and has OEM wheels.
    I will investigate the octane adjust first as engineeringmike suggested.

  6. #6
    Tuner in Training
    Join Date
    Nov 2021
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    25
    I was investigating this issue further and I noticed, that the low rpm knock occurs mainly while half-clutch when taking off. What do you think of it? Has anyone noticed knock in these areas?

    Car is manual transmission.