Audible Knock, no KR

[Maxwell Power]

I did a search and found some similar questions but no actual answers.

WOT, Audible knock heard from around 4800 to 6500rpm. Zero KR on the log.
At first I though rocks flew out of the rear tires and hit my dyno room door. But the second time it was obviously knock. It's a rapid fire of multiple knock events so I can only assume it's on multiple cylinders.

The car is an 05 CTS-V.
K&N intake
Kooks Headers with High flow cats
Magnaflow exhaust

Other than that it's stock. Plugs are only 8k miles old. New wires, new MAF, new O2's.

Is it common that the Knock sensors don't pick up knock?

By the time you guys look at the tune and log, I will obviously have already lowered the timing dramatically. I was just trying to figure out if this car has bad knock sensors or if there is something I need to know about the knock system on this car under WOT.

Thanks,
Dominic

[Maxwell Power]

Here is the tune as I'm pulling it off the dyno.

Any tips or pointers?

Criticism is welcome... just try not to be too hard on me!

I've only tuned about 8 LS powered cars at this point. I've tuned thousands upon thousands of other engines. Been tuning since 93 (started on carbs like most of us) so I'm no stranger. However, the LS series is a bit new to me over the last year. I'm a little late to the gang bang, but I'm always up for learning.

[Maxwell Power]

and here's the graph

[GPGTP]

Did you try to pull timing to see if it went away?

The knock sensors should still pull timing, yet I'm experiencing a similar thing. In your case I would suspect something mechanical.

[WS6FirebirdTA00]

Boy that MAF is jumping all over the place and pulling in some higher timing as it drops the g/cyl value. That is high timing on that setup IMO.

Double check the knock sensor setting and make sure they aren't adjusted too high. Although it is a pain, you can also test the knock sensors to make sure they are actually outputting the signal as they should.

Also make sure the dyno isn't over loading the car. I have had cars show knock on the dyno just because of the high load and did fine on the street.

Personally, I would not be putting in as high of timing as you are. Low 20's in the high load is more than enough to make power.

[Maxwell Power]

I really hate how much the MAF bounces around. It was similar on the stock MAF and only made worse by the K&N. Now, I've started to log the MAF value after filtering. Obviously the value we see is non filtered as it's the SAE OBDII reading. Actual MAF value used by the ECU is different. You can see how well the filtering works by looking at cylinder air. The cylinder air isn't bouncing up and down as bad as the MAF signal. It still bounces a little though. I'm going to increase the filter value and see how that helps.

You are correct about my timing. I have since pulled a bit more.

any advice on reducing the choppy MAF behavior?

[racerx203]

I really hate how much the MAF bounces around. It was similar on the stock MAF and only made worse by the K&N. Now, I've started to log the MAF value after filtering. Obviously the value we see is non filtered as it's the SAE OBDII reading. Actual MAF value used by the ECU is different. You can see how well the filtering works by looking at cylinder air. The cylinder air isn't bouncing up and down as bad as the MAF signal. It still bounces a little though. I'm going to increase the filter value and see how that helps.

You are correct about my timing. I have since pulled a bit more.

any advice on reducing the choppy MAF behavior?

I had the same problem. Had audible kr it was like rocks or steal banging freaked me out beCAuse it didn't show up on log. It didn't even pull timing so i messed with the sensitivity chart. mine were set high 10, 9.5. I started to lower this by halfs(.5) till it started to pull timing before it kr. I ended up 8.3 on the sensitivity chart but then started to have it pull to much timing without audible kr. It's a fine line with the sensitivty adjustments so i went backt to desensitise and just pull timing down till i don't get AUDIBLE kr. My final timing is 13.5*. I wasn't fimiarl with high boost timing. I was around 20* at 10psi of boost but when i upped the boost to 24psi i didn't lower the timing, so i ended up at 13.5* which is about right with my set up. I don't care if i see kr on logging as long as i don't hear it my engines fine. Which it has been for over 10k miles.