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Thread: False Knock Diagnosis

  1. #1

    False Knock Diagnosis

    I have an exhaust rattle coming from my right header merge collector on cold starts.
    It goes away as the car warms up but returns when race hard.

    The knock retard I get on my scanner are little blips here and there no more than a degree or two for a millisecond. I also noticed on day when I was filming a launch that my exhaust rattles violently.

    Can this be the reason for some unexplained loss of power? Checked everything mechanically and electrically to rule it out

  2. #2
    Senior Tuner mowton's Avatar
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    post your tune and logs with your .cfg

    Doesnt sound like alot of knock. To diagnose, cut the timing about 3 degrees in the area of knock and see if the KR stays, if it does it is probably false.

    Ed M
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  3. #3
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    Quote Originally Posted by Pabs1 View Post
    I have an exhaust rattle coming from my right header merge collector on cold starts.
    It goes away as the car warms up but returns when race hard.

    The knock retard I get on my scanner are little blips here and there no more than a degree or two for a millisecond. I also noticed on day when I was filming a launch that my exhaust rattles violently.

    Can this be the reason for some unexplained loss of power? Checked everything mechanically and electrically to rule it out
    Year/model?

    And is it knock retard or burst knock retard or do you know? Log all the KR PID's you can find to see where it's coming from.

    Wouldn't surprise me if it's false knock. Follow Ed's suggestions.

    You can also get some Torco (octane booster) to help with diagnosing this. If you pull the timing back a few degrees and up the octane and it STILL shows up as a little KR here and there, it's very likely false. If it goes away after doing either of those, then I would think it's likely real.