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      08-30-2012, 04:55 PM   #45
Mike Benvo
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Drives: Harrop SC M3 / E46 M3 / 7Turbo
Join Date: Apr 2008
Location: SoCal

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2008 BMW M3  [5.00]
1990 BMW 735i Turbo  [5.00]
2004 BMW M3  [0.00]
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Quote:
Originally Posted by m3an View Post
this may not be your case but is worth mentioning. Knock sensors are sooooo sensitive that you may not hear audible knock (if you do it's prob too late anyways).. Being that each cyliner has individual sensors, timing can be pulled from one cylinder and you wouldn't realize it. there is also "phantom" knock which can be caused by harmonics that acutally give the knock sensors a false reading and cause the symptoms mentioned. My first start would be the simple things; plugs, injectors, take a look at the fuel pump and filter.. You really need to do some datalogging to see what is going on as everything is just speculation at this point
I would have to disagree here as I have heard audible knock on many occasions, even with stock software targets for ignition timing and stock knock sensitivity settings. Hearing knock doesn't mean that it's too late, unless we're talking about extremes. I see the knocking more in high load/lower RPM situations, more than full throttle, high RPM.

This car doesn't have conventional knock sensors to 'listen' for knock, rather, it measures plug electrode resistance to determine if there was an issue during the cumbustion process.

I don't think this is a knocking issue. Checking the adaptation values might provide further insight into what is happening, and of course, as you said, datalogging would be a big plus.
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