How to get false knock
10-06-2004, 02:55 PM
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How to get false knock What I've noticed from data logging with HP Tuners is that I get random amounts of false knock here and there. Nothing huge anymore. But...
One thing I've finally concluded is that the way you drive can cause false knock. I don't know if any of you have noticed this yet or not. I've noticed if I attempt to scratch 2nd gear I will get a full 4* KR as soon as I'm in 2nd all the way until I go to 3rd. Now if I just wind up engine and shift easily from 1st to 2nd, I will get zero KR. Makes sense now doesn't it? The PCM is seeing an unusual amount of resistance out of the blue. So bam false knock. Shifting more gently I don't get any KR.
Has anyone else noticed this yet?
One thing I've finally concluded is that the way you drive can cause false knock. I don't know if any of you have noticed this yet or not. I've noticed if I attempt to scratch 2nd gear I will get a full 4* KR as soon as I'm in 2nd all the way until I go to 3rd. Now if I just wind up engine and shift easily from 1st to 2nd, I will get zero KR. Makes sense now doesn't it? The PCM is seeing an unusual amount of resistance out of the blue. So bam false knock. Shifting more gently I don't get any KR.
Has anyone else noticed this yet?
10-06-2004, 05:55 PM
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May be that a detonation, because it can't dump its
heat by expansion, elevates the cylinder / head
surface temp instead and, since this takes finite
time to relax & get thermally conducted out to the
water jacket, the flash surface temp can then add
to the ping problem, making more heat....
heat by expansion, elevates the cylinder / head
surface temp instead and, since this takes finite
time to relax & get thermally conducted out to the
water jacket, the flash surface temp can then add
to the ping problem, making more heat....
10-07-2004, 01:39 PM
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Sounds like you are describing tip-in knock. Punch it and downshift and the KR comes along. This is due to the rapid increase in engine load and cylinder air - with a slight (millisecond) lag for the fuel to catch up and make the correct mixture. A small, quick lean spike resulting in a single ping on the scanner.
My instances of false KR have come in two flavors. 1) dang asp pulley caused false KR under high load. 2) low load cruising - no throttle changes, just a small blip of KR out of nowhere that decays away quickly. could be road debris, rough roads, TCC locking/unlocking, or ???. Once or twice I have seen false KR from driving over something like a railroad crossing.
My instances of false KR have come in two flavors. 1) dang asp pulley caused false KR under high load. 2) low load cruising - no throttle changes, just a small blip of KR out of nowhere that decays away quickly. could be road debris, rough roads, TCC locking/unlocking, or ???. Once or twice I have seen false KR from driving over something like a railroad crossing.
10-07-2004, 05:47 PM
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Yeah that makes sense deezal. I just get those little spikes, or blips of KR here and there. LOL I remember I had one that was 0.2* KR. I'm glad I only get false knock here and there, nothing serious.
