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Discussion Starter #1
I looked at all 4 cylinders for this setting on the AP.

Cylinder 1 and 2 were at 0
Cylinder 3 at 1
Cylinder 4 at 6


What does this mean??

my Dam is at 1
 

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I was about to ask this same question.

Was this on the highway or around town? For reference, I saw 20-30 knock-sum around two, but no incremental change once I got on the highway. Once I got to where I wanted to be 2 hrs later, the knock sum began to climb.
 

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Discussion Starter #4
I know what DAM is, im wondering about the knock cylinder sum (there is an option for each cylinder) i was reading on Nasioc that the sum doesnt really mean anything because if it doesnt decrease your DAM then it isnt severe.

Just wanted to make sure.
 

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It's exactly what it sounds like. It's a sum of all knock events counted in each cylinder. Here's the important part: it still adds to the sum at low rpms where false knock occurs.

Took this info directly from the ATR help file monitor list.
 

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The knock sum value itself is irrelevant as it is even incremented at idle and low load/RPM where the Subaru knock detection is very poor at determining knock (which is why the ECU does not respond to these perceived knock event in that area).

For knock sum, you want to look at when it increments at moderate to higher loads. For ECUs that support the per cylinder knock sum, you tend to see more counts in cylinder #4. Presumably this is because the knock sensor (possibly due to its placement on the block) picks up noise better in that cylinder than the others. This is likely also the reason why the OEM tune has positive timing correction in cylinder 4 (in later Subarus). The idea could be to induce knock first in the cylinder that is most likely going to picked up by the knock sensor and therefore, allow for a quicker response for all cylinders (since timing is not pulled on a per cylinder basis).

Bill
 

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The knock sum value itself is irrelevant as it is even incremented at idle and low load/RPM where the Subaru knock detection is very poor at determining knock (which is why the ECU does not respond to these perceived knock event in that area).

For knock sum, you want to look at when it increments at moderate to higher loads. For ECUs that support the per cylinder knock sum, you tend to see more counts in cylinder #4. Presumably this is because the knock sensor (possibly due to its placement on the block) picks up noise better in that cylinder than the others. This is likely also the reason why the OEM tune has positive timing correction in cylinder 4 (in later Subarus). The idea could be to induce knock first in the cylinder that is most likely going to picked up by the knock sensor and therefore, allow for a quicker response for all cylinders (since timing is not pulled on a per cylinder basis).

Bill
back from the dead.... I'm seeing knock sum numbers exceeding 130+ even 180+ from this most recent data log I collected for my tuner. Am I doomed?
 

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I would like some confirmation as to how the ECU determines exactly what cylinder is knocking.

Is it using a sensor, like the crank position sensor? Or ?
 

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The knock sum value itself is irrelevant as it is even incremented at idle and low load/RPM where the Subaru knock detection is very poor at determining knock (which is why the ECU does not respond to these perceived knock event in that area).

For knock sum, you want to look at when it increments at moderate to higher loads. For ECUs that support the per cylinder knock sum, you tend to see more counts in cylinder #4. Presumably this is because the knock sensor (possibly due to its placement on the block) picks up noise better in that cylinder than the others. This is likely also the reason why the OEM tune has positive timing correction in cylinder 4 (in later Subarus). The idea could be to induce knock first in the cylinder that is most likely going to picked up by the knock sensor and therefore, allow for a quicker response for all cylinders (since timing is not pulled on a per cylinder basis).

Bill

What if I have a constant knock sum of 2 when driving at cylinder 3&4? What does it mean??
 
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