dynamic airflow and burst knock

[draz53]

Trying to track down a knock retard (tip-in) problem. I thought it might be burst knock, but logging BK it's alway 0. To double check this, I'm looking at logged dynamic air vs the values in the "Burst Knock Enable Cyl Air Threshold vs. RPM" table. To do that I need to get dynamic air per cylinder (is that right?). Someone posted that you do this by looking at the frame-to-frame difference in dynamic air and dividing by 8, but that can't be right because those values are much larger than the table values, it would awlays be in burst knock mode. So how do I calculate the correct dynamic air per cylinder, to compare to that table in the tune file?

[draz53]

Well I guess no-one knows, but now I came across some posts saying burst knock does not show up as KR, it just pulls timing... is that right? So looking at BK won't help solve a KR problem?

[Russ K]

Well I guess no-one knows, but now I came across some posts saying burst knock does not show up as KR, it just pulls timing... is that right? So looking at BK won't help solve a KR problem?

Yes, burst knock does not show up as knock retard. But if you disable burst knock retard, then you may get actual knock retard during sudden throttle opening. You can log cyl air, no calculations needed.

Russ Kemp

[draz53]

OK, well than this is confusing. I'm looking at the raw log data, which includes KR, burst knock, and cyl air. At the start of the first KR event (which lasts for 15 frames), the delta cyl air (frame - previous frame) is definitely over the limit in the "Burst Knock Retard - Enable Delta Cyl Air" table, but the reported burst knock stays at 0. So seems like it either should have shown BK more than 0, or BK showed up as KR, or the BK pid isn't working. The sequence of 4 delta cyl air values starting 1 frame before the KR shows up is .04, .05, .03, .03, all above table limit values. (But there are two other KR areas where delta cyl air does not go over table limits.)

The KR/BK table values are stock for 2000.