Originally Posted by Smile83
I read a few threads here on knock readings and cant find a solution. My problem is cylinder 4 is picking up knock sum and also pulling between -1 to -4.9 timing. My tuner suggested it could be a cracked ringland or an external noise. We cant seem to locate the external noise. Could it be a cracked ringland causing the knock reading? Can it be tuned out?
Side note: Not smoking and good compression across the board. New spark plugs. Also datalogged with no knock event in 3rd gear WOT.
Tomei Type-S FPR
Knock sum values are irrelevant in and of themselves and cylinder #4 will usually be higher due to knock sensor orientation. The reason why knock values have no meaning is that they are also incremented at idle and low loads when the Subaru knock detection is extremely poor at distinguishing knock from other engine noises. The only use it has is to look at when it increments when false knock is less likely (at higher load). It useful to monitor this as it can be tricky to see when learned events for fine knock learning have actually occurred as they are learned and then re-applied over and over until they ramp back to zero.
You said timing was being pulled? If it is not shown in feedback knock correction or fine knock learning columns (or DAM has not dropped), then it is not due to knock. A current knock event from the above would be shown as a increment to knock sum in one (or more) of the cylinders.