Anyone have a good timing table that won?t knock itself to death on 87 octane? I have my 15 Silverado tuned. In logs it shows a good bit of knock on 87 but it?s not audible. With 93 it shows no knock. I haven?t adjusted timing tables very much. Just 3-4 degrees and no luck . Fueling is Dialed in to within 3% with a wideband. Appreciate the help as always
Post a log and tune
FINAL AND DONE WB 11-4.hpt current tune.
log.hpl last good log i have from tuning with wideband cant remember if i was running 89 or 93 at this time. still either way none of the shown KR was audible knock.
truck runs perfect. i have been running 93 in it for several months. just would like to be able to run cheaper fuel sometimes. i ran 87 all the time before i tuned it and had no issues, however after dialing in the fuel with a wideband and getting it right it shows knock on 87. usually 2-3 degrees at times. nothing audible. with 93 it never shows any knock. cam timing hasnt been touched. injection timing hasnt been touched. truck is all stock except k&n air filter and magnaflow muffler.
Last edited by TZTuning; 01-27-2024 at 09:21 AM.
Had no knock whatsoever in this truck. You are welcome to try this file. You may try setting pe to 1.21 across the board if knock persists.
Also be careful with your torque and driver demand settings. I forget which torque limit but one of them will kick pe out.
I’ll give it a looking over. And compare. It seems to want to show it more cruising than under wot (2:24.3:00,3:29,3:52,6:50,8:17,8:54) minute marks in the log i notice. it does it a little under WOT but nothing is audible and it doesnt hurt performance of the truck at all that ive noticed. Like I said that was the only decent log I had saved for it that had any length to it.
appreciate the edit. im looking over that now.
Last edited by TZTuning; 01-27-2024 at 07:48 PM.
is it a stock truck?
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All stock except exhaust,k&n air filter , and a catch canOriginally Posted by MeshaalMMT
What is going on with 87 octane is it starts to knock a little then the computer moves toward the low octane table. Then after a few seconds of no knock it tries moving back toward the high octane table until it starts to knock again and the process repeats. It is honestly normal behavior for them to do this on low octane fuel. The only way it wont is if you set the high octane table to be the same as the low. Like this it will run fine but lack power. You can use this to work on the low octane table to get it to make power like that then put the high table back to normal.
That's an interesting behavior I forgot about.
In my particular case, I'm trying to troubleshoot a knock issue I'm having on my Gen V L83 5.3 on 87 octane and it totally slipped my mind how the OS determines the octane content of the fuel. I knew it had an alcohol content sensor but forgot that it also switches between high and low octane spark tables following a feedback control mechanism to discover/learn the most efficient spark advance without knock.
The problem I am having is right after I flash the ECM it selects a spark advance at the average of the high and low spark advance table (makes sense), and when I drive it in a certain region (3800 rpm, 100% load) it produces knock. I get out of it and then back into it a few times and after 4 cycles or so it stops knocking. That seemed weird to me, but now makes sense. Looking back at the log I see it's using the low octane spark advance in that region after the 4th time, and doesn't knock.
Is there a variable that we can log which shows what the current ratio it's using between the high and low octane tables?
Is there a table or parameter which controls the rate it uses to oscillate between high and low octane spark tables?
Try adding the Learn Factor channel. I believe 0 is high octane table and 1 is low and anything in between is a blend. Similar to Octane Adjust Ratio on Fords.
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