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Old 04-28-2009, 09:01 PM   #1
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Default knock spike on datalog

Ok, I've heard knock before (not on my car thankfully) I've been in the process of tuning spark while datalogging after adjusting my CAS (base timing was off) . I datalog, and retard the timing to knock down the spikes.

I started thinking: I don't really know what knock looks like on a datalog. I know what mine says is knock, but I have a tough time believing a single random sharp spike is knock. Wouldn't knock be sustained in the log for as long as there was load, or at least until it moved close to a cell where the timing was more to its liking, not spike and disappear?

Anyway, can someone post a pic of a datalog with knock going on? I don't want to pull spark unless i"m sure there is knock. I checked my plugs after a run yesterday, and they looked fine.
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Old 04-29-2009, 11:12 AM   #2
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Since no one want to chime in, I'll throw up some pictures. The first one is what looks like real knock sustained over a longer period of time.

Here is the random spike that I'm wondering if I should mess with the timing or leave it be.

Question is: How would all of you tackle this problem> lower timing over entire region that I see knock, or just reduce timing at the large spikes and see what that does. I lowered timing across the entire region.
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Old 04-29-2009, 11:20 AM   #3
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What RPM is that at? Mine does it between 4K and 4500K almost every time at any MAP pressure. I ignore it now.
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Old 04-29-2009, 12:00 PM   #4
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The knock in the first image is about 5200-6500 at 180kpa
The second image (single event) is 4843 164 kpa.

I really think that I am going to start ignoring loan spikes when datalogging, and only adjusting timing if I see a pattern like the first image.
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Old 05-05-2009, 03:50 AM   #5
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Would you mind posting/sending me those log files? I could really use them for a class project.
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Old 05-05-2009, 12:42 PM   #6
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Sure, I'll send you the logs. Is there something in particular you are looking for in a log? Send me a pm with your email. Do you have dataloglab so that you can open the log, or are you looking for still images?
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Old 05-05-2009, 06:57 PM   #7
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Build yourself a set of detonation cans. Electronics will tell you what they think is knock. I love my Knocksense (it's great when I'm on track and not really listening to the motor), but if I'm actually tuning or listening I'm wearing my cans.
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