Intermittant KR Issue with o.s.3 and 3 bar???

[nitrorocket]

I have a wierd intermittant KR problem just as the motor enters boost, 105-115 kpa in the 3600-4200 rpm range. It is not there all the time and I have a perfect AFR and a commanded timing of 18 degrees. I hget it under full or part throttle, doesn't matter, it still shows up "sometimes". Full boost from 115 KPA up to 230 KPA will have no knock but my timing will retard a couple degrees. I think the retard my be due to the KR I am seeing at 105 kpa??

I set the desired timing table to 18 degrees timing, The high table to 18, and the low table to 17 degrees for WOT. Should I have the high and low octane tables the same??


Any insight? Is there a possibility I have my software setup incorrect? Can I be getting burst knock with a custom SD no MAF tune??

[Tordne]

You could sure be getting burst knock. But - I would expect you to be noticing other irregular knock if it was Burst Knock related. You could always try 0ing out the tables and see :) I have Burst Knock disabled al the time!

[nitrorocket]

Do you know off hand what table I would have to 0?? How does burst knock work with a SD setup when there is no MAF?? Is it calculated off RPM and VE position? Sometimes the knock will happen at slightly different areas, but it is always .4 or less. When I hit boost (18 psi setting) it revs so fast, I have had problems with the EFILIVE skipping data log cells the more boost I run. When I had a lower bosot setting I did not have this problem. I have been raising the amount per second of recordings to try to get all the cells recorded.

[Tordne]

I just 0 out both B6210 & B6212 tables. Burst Knock works in both MAF and Speed Density the same way. It basically detects a change in the g/cyl which in Speed Density is logged with PID GM.DYNCYLAIR_DMA. Basically the same way it knows with column to reference in the spark tables.

[nitrorocket]

Burst knock is only for tip in or ultra fast engine acceleration correct? The regular KR settings will cover heavy load KR?

[Tordne]

Burst Knock is for various changes in air density. The idea is to proactively remove timing so to try an curb the occurance of real knock.

In all the testing I have done with various values in the Burst Knock tables, for me Burst Knock being enabled ALWAYS causes Knock Retard to be logged much more than if it is disabled. I also found the same on a couple of MAF cars, which surprised me. They were also better with it disabled!

[joecar]

When the PCM sees a change in airmass greater or equal to the BK delta table B6210, it uses the BK retard table B6212 to pull timing;

As Tordne said, the PCM guesses when real knock is about to occur and tries to prevent it by premptively pulling timing at that point, unfortunately it guesses too often, I found this too, and I have since zeroed my BK.

Joe

[nitrorocket]

I think I found the problem, I looked at my logs frame by frame and I noticed my Spark table was diping all the way down to .40 air mass at 2400 rpm. I had the timing to high right there and for the instant It was there it started to KR.

I will have to make another run now that I lowered the tining in those cells. Sure is wierd, I startmaking boost at 2400 rpm, and the boost does'nt max out untill about 5500 rpm. sure seems like a long time for boost to peak?