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Hi All,
I have my wideband all hooked up and scanning properly. (I think). I am getting a crap load of knock at WOT and a few other areas. It looks like my trims and AFR are in the acceptable range. I'm not sure what I am missing in my tune!! Is there anyone who could look at it and point me in the right direction? I greatly appreciate any suggestions!! Attached is a copy of my tune and recent scan.Attachment 87502Attachment 87503
2007 Grand Prix GT Supercharged.
It's not a good idea to mirror the timing tables, the low octane table needs to have less timing so the computer can reduce the timing and help remove knock. You also have the computer trying to add in an extra 4 degrees of timing based on the base fuel spark corrections.
I'd yank back the timing to 10 degrees and see if it still knocks. You should be logging your cylinder airmass so you can see where it's following your timing curve.
Thank you very much 5FDP!! I reset my timing and adjusted the .92 timing to 10. I also zero’d out the base fuel spark correction so it doesn’t try to add timing. I will research how to chart the cylinder air mass then go for another scan in about an hour or so.
I will try some scans tomorrow with suggestions you made. I could not find a how to on the cylinder airmass chart so I made one myself. Hopefully it is what was needed.
I scanned this morning with the new settings. They seemed to help a lot but still knock. I logged the cylinder airmass but I really do not know how to decipher it???? I noticed during some of the knock episodes that the AFR was 15.7 following the chart vs time. The trims seem to be in line though (except a few of the lower hz cells. Are there anymore adders or subtractors that I should adjust?
Attachment 87535
Attachment 87536
Your timing tables has two axis, one is cylinder airmass and the other is engine RPM. You can create a graph that use both of those, then you can track exactly where the computer is using your timing curve. Though being that the timing table stops at 0.92 cylinder airmass it's likely to stop right there most of the time.
Also currently your low octane table is higher than the high octane table, so it's trying to add in timing when it see's knock instead of taking it away. Just copy the high to the low and minus 2-3 degrees from the entire low table.
It's going to be a game to play of how much timing and fueling it wants to stay out of knock.
Sometimes 11.0 is too rich and 11.5 or 11.8 is just right. See where you end up at at. I'd say anything at or under 1.0 degrees of knock is nothing to worry about.
I battled knock for a long time in my 2000 GTP on 93 pump gas. In the end I had to run 12-14 degrees of timing with a air fuel ratio of 10.5-11.0 just to keep it happy all the time on 8-9psi. I also ran a stock thermostat to help keep the engine temps up around 190-195. I never did replace my knock sensors with new AC delco ones just to rule them out, didn't keep the car long enough to try that.
I see what you are taking about with the High and low. I went ahead and did what you recommended for the low. It seems like a never ending knock battle with these 3800s. I'm just going to find the settings with the least bit of knock and hope for the best. I was going to put it on meth or E85 but too much money. I replaced the rear knock sensor with a new delco 1 1/2 years ago. I appreciate the help 5FDP