Timing - Knock Retard Histogram
and here is a sample of a log with some knock, truth be told this was supposed to be my longer drive, aka 20 or 30 minutes, but the log stopped recording, (hey just being honest with you all, it happens) let's just say that HP Mini netbook is no longer with us, ha ha!
anyway this is a good screen shot to share two observations regarding engine knock:
1. some engine knock is acceptable, after all if you log your factory tune for the first time you will see some knock, so the GM engineers are cool with that. I would think less than 1 degree retard is ok, that is for daily driving occuring here and there, if it's always in the same cell then by all means do something about it
2. False knock, without proper audio equipment to truly verify if our know is actual engine knock we really have no way of knowing. Again for stock engines and normal driving the stock knock sensors will do and we can rely on them, however if you were to heavily modify your engine or transmission you may experience false knock. This is yet another reason why minimal knock ie less than 1 degree can be tolerated.