HELP with KR on 2003 5.3 Tahoe

[Nestorxg]

I'm happy with SD, MAF and fuel trims but there is knock between 2400 and 3200 rpm that I'm not understanding. I don't think it is false knock because it shows up at the same spots. I have halved underspeed/overspeed and lowered high and low octane tables by 1.5 at that RPM range. I haven't gone lower because sometimes it is as low as 1 other times 3 and I don't think lowering it is doing anything.

log after flex fuel disable.hpl
after sd tune 10 and disable flex fuel command 14.68 and turn on CL.hpt

[Nestorxg]

Anyone?!

[gametech]

The rpm range where I get definite false knock in my cammed ls1 with pac beehives and factory rocker arms is about 300-400 rpm lower than yours, but that could easily just be caused by the difference between 5.3 and 5.7. To be sure, just take a big whack out of your timing tables in that area and see if the kr is still there. If you pull 5 degrees out of an area that showed 1 or 2 degrees of retard, it should make things obvious whether the kr is real or not.

[04silverado6.0]

That ve looks rough and definitely needs work. Im thinking the knock will go away by working on the pe settings and getting the ve looking good. Why was the flex fuel disabled?

[horsepowerguru427]

I agree. The VE is too choppy. Smooth it out and enable PE.PE enable.jpg Change PE throttle tables as well PE throttle.jpgYou might even add a percent or 2 to those corresponding VE cells, since its lean right at the knock. Lean at knock.jpg Also, Lower the timing in those cells a degree and smooth the edges into the rest of the table. See if those changes help and log again.
Log more knock channels including burst knock and try to determine exactly whats identifying the knock. What exhaust do you have? Ive seen stock exhaust on some trucks cause knock in this area under load. Headers and y-pipe with no other change and the knock went away.

[Nestorxg]

Thank you all for the great ideas. I'm going to play around with the tune some more. I did suspect my stock exhaust but the cheaper route is trying to tune it out. If the tune doesn't make it better I will drive it easy until I get a hold of good headers. I notice most of the knock going uphill so to me that points more towards the exhaust being a problem.

[Nestorxg]

That ve looks rough and definitely needs work. Im thinking the knock will go away by working on the pe settings and getting the ve looking good. Why was the flex fuel disabled?

The flex fuel was disabled because the commanded AFR was too rich for my liking. We don't have E85 around here so I didn't think twice about keeping that on. I was fighting AFR error logs showing 4-5% rich everywhere and was not able to get it down from there. Disabling flex fuel and commanding 14.68 at least gave me something consistent to look at in the logs. Now, logs show +-1% AFR mostly everywhere. Besides the knock, I was pretty happy with that.

[Nestorxg]

Here's my current tune with smooth VE and log with knock. I logged these before your responses.
after sd tune 17 smooth entire VE table.hpt
after tune 17 log with knock.hpl

[04silverado6.0]

I see you have not failed the maf. It may be better in your case to go back to stock ve, turn flex fuel on, maf tune only. Also i would use lambda err, dont bother looking at the stoich and commanded afr in the scanner. After the maf is dialed in you can go back and tune the ve.

[04silverado6.0]

Here is a stock 04 silverado file i read off from a truck my grandpa bought. This ve table i would imagine is very close to what you will end up with if your flex fuel is fully re-enabled. Not saying to use it but that will be the general shape and values with a e10 stoich.