Tip In Knock --Timing MAP has No effect at WOT -- ALways get Retard

[rcwilbur]

I have Texas Speed 5.3 heads and 224R cam in LS1 Corvette with Manual transmission. AFR is 12.5 at WOT and I'm getting a lot of knock retard. PCM is taking away as much as 10 degrees timing. I started with stock tune which had about 26 degrees of timing at WOT and have steadily reduced timing in about five different steps. Last run I set timing to 16 degrees at WOT. It doesn't seem to matter what the timing map is set at, the knock retard is always removing about the same thing 10 degrees.

Could it be that the knock sensors are too sensitive?

[edgZ06]

Yes, do you hear any knock?

[SSUte01]

If it's always removing 10* (which is the default max in many std OSs), I would look to either sensor itself or quite probably the harness integrity.

[SultanHassanMasTuning]

best is to have knock box or add race gas and see if knock goes away. its possible that the characteristics of the new heads and cam create vibrations and noise the the knock sensor is picking up.

does it pull knock by free revving?

[rcwilbur]

Yes, do you hear any knock?

I played with the knock sensor settings and think I've got this under control. I'll tell you what it was doing and the adjustments I made.


No. I didn't hear any knock, but it is pretty loud at that point in the WOT--about 4400-5000 RPM. What it was doing was producing a single
sharp spike of retard followed by a long decay (but apparently no repeat knock triggers).

I spent a lot of time looking at other tunes on the repository and noticed that the 2001/2002 ls6 corvette tunes had different knock sensor settings. Under the assumption that the higher settings were a result of the increased compression of the ls6 vs. my stock 99 ls1 I copied the LS6 sensor settings to my tune because the new heads on my LS1 produce about 10.9 to 1 compression vs. stock of 10.1 to 1. I also decreased the attack and the decay levels by about 15%.

I then made sure the timing was in an area that should be safe and increased it until a saw a little knock and then backed it off a little. As a result of all of this I have the car running at 23 degrees at WOT with no knock retard and don't hear any evidence of knock. Not sure if this procedure is a good one, but it seemed to work. I hope I don't end up blowing anything up!!! Thanks.

[rcwilbur]

I did look at the max knock table, and it is set to 10. I was getting something different everytime. Sometimes 6, sometimes 8 sometimes 9. It was generally a single sharp spike to that level and then a long decay without any additional triggers.

[rcwilbur]

I did look at the max knock table, and it is set to 10. I was getting something different everytime. Sometimes 6, sometimes 8 sometimes 9. It was generally a single sharp spike to that level and then a long decay without any additional triggers.

Here is the tune I ended up going with and a log of the last test run. The knock sensors in the tune are pretty much the settings from the LS6 standard tunes, with a little modification to the attack rates and the decay.AddWideband1.cfgclosed loop 20 (TIming) Run (4-6-13).hplTune After Heads Cam (Installed 4-6-13).hptAddWideband1.cfgclosed loop 20 (TIming) Run (4-6-13).hplTune After Heads Cam (Installed 4-6-13).hpt

[rcwilbur]

Didn't attach the files correctly. Here they are.