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Old 09-26-2010, 05:06 PM   #1
Tripintaz
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Default Fine Knock Learning in ATR

While on the dyno and even on the street I can see the "Fine Knock Learning" column start pulling timing. It is usually about -1.4 but i have seen it go to -2.8 and starts at 5100 RPMs.

Now the weird thing is that when we flashed in Cobb Stage 2 boost levels, then reset the ECU and made a pull, the FKL was still showing it was pulling timing above 5100 RPM but there was still no knock activity. The ECU was not picking up knock, but it was pulling timing in the FKL table.

I am confused. Wouldn't the FKL table only pull timing based on what it learned from the knock correction tables?

If the ECU did not pick up any knock, how would the FKL table have a learned amount of timing to pull right after an ECU reset?

Anyone have any input on the Fine Knock Learning tables and how they work exactly?

I dont understand how the Cobb Stage 2 timing and boost levels were casing this table to pull up to 3 degrees of timing in the FKL table every time we made a pull on the dyno and then I was able to replicate it on the street.

Thanks,
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Old 09-27-2010, 09:33 AM   #2
Cobb Tuning
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Fine knock learning is the ECU's means of fine tuning timing at the current DAM. When the DAM changes, the fine knock learning table is cleared. If the fine learning drops in a particular cell, that, in and of itself, is indication that there was a knock event. If the DAM drops, that is an indication of a knock event. If the feedback correction drops, that is also an indication of knock. These are three responses to knock for which only one can change at any given time in response to a knock event.

Logging "knock activity", unfortunately, is not an accurate means of determining all knock events. This is because the time scale of a knock event is extremely small and it is difficult to catch it when logging. It is better to look at the 3 knock responses described above. The DAM and fine learning are learned values, so you can see it drop. Feedback correction is held for a period of time well after the knock event (relatively speaking), so you are able to "catch" it in the logs.

That said, you will have some knock response at times, regardless of the tune. The Subaru knock detection is less accurate at lower RPM/load where you are more likely to get false knock. The higher the load where the knock event occurs, the more importance you should place on the knock event.

Bill
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Old 09-27-2010, 01:22 PM   #3
Tripintaz
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Makes sense.

I will just add more fuel up top and see how it reacts.
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Old 09-28-2010, 05:00 PM   #4
Tripintaz
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Ok so I took away 1 degree of timing from the dynamic advance and adding a touch of fuel. Now it is happy with no more Fine Knock learning.
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Old 10-01-2010, 09:08 AM   #5
Tripintaz
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I take that back. It is still pulling 1 degree of timing in FKL. Lame.
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Old 10-01-2010, 09:31 AM   #6
Cobb Tuning
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Quote:
Originally Posted by Tripintaz View Post
I take that back. It is still pulling 1 degree of timing in FKL. Lame.
The ECU will remove 1.4 deg. from the current cell in that table per knock event for your ECU (add 0.35 deg. for no knock over a period if held in that cell up to a value of 0 if DAM is at max). There isn't a tune anywhere that is not going to have some sporadic correction in the table over time. The higher the load, the higher the RPM, the more consistent the correction, the greater the correction, the more emphasis you should place on it. If it meets this criteria, I would look at pulling timing first, rather than addressing fueling, unless you have a reason to believe your fueling is off.

Bill
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