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Old 09-02-2011, 10:36 AM   #1
Sheltonmega
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Member#: 265204
Join Date: Nov 2010
Chapter/Region: MAIC
Location: Fairfax, VA
Vehicle:
2009 WRXCobbProtuned
CattedAEMCAIPerrinTMIC93

Default Constant Fine Knock Learn at low rpm

I am having Constant less than 0.7 degree Fine Knock Learn at low rpm medium load, it goes away over 3000 rpm at high load. Is it a problem?

Thanks.
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Last edited by Sheltonmega; 09-02-2011 at 01:21 PM.
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Old 09-03-2011, 09:55 AM   #2
Cobb Tuning
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Fine knock learning at low loads is normal, especially when it is single counts (-1.4 or -2.0 depending on car). In your case, it has actually learned back to zero a bit (does so in increments of 0.35 deg.).

Fine knock learning is a learned correction, so the engine control unit (ECU) perceives a knock event when conditions dictate that fine knock learning is active and then makes a correction to the appropriate cell (each cell is based on a specific load and RPM range). So, for example, let's say one cell is 3000-4000 RPM and 1.0-1.75 g/rev of load. You are driving and the ECU perceives a knock event at 3200 RPM and 1.2 g/rev of load and fine knock learning changes are allowed. So, it drops that cell to -1.4. Now, everytime your RPM is between 3000-4000 and load is between 1.0-1.75 g/rev, you will see that correction (-1.4). Doesn't mean you are knocking when you see that value -> it is just a learned correction based on a past knock event. That is, the ECU is basically tweaking the timing based on these perceived knock event. If it finds that the knock doesn't occur in that cell again (based on specific conditions), then it will slowly ramp it closer to zero (in 0.35 increments).

Regardless of tune or car, you will always see the occasional knock correction, especially at low loads. This is normal. Where it is a concern is when you see consistent corrections at high load (such as during wide open throttle) that is not due to shifting or mashing the throttle. Or when you see consistent large corrections (-4.2, -5.6, etc.).

Bill
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Old 09-05-2011, 08:52 AM   #3
Sheltonmega
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2009 WRXCobbProtuned
CattedAEMCAIPerrinTMIC93

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Thanks Bill.
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