New, to me, 2008 Silverado with tons of KR with 87 or 93 octane gas

2008 Silverado, 63,000 miles, 5.3, 4L60E, 3.73, NON Flex Fuel, with AFM, seems to run very well, but shows a LOT of KR at random times all over the datalogs

My old 2002 5.3 Silverado (same drivetrain numbers) allowed a good amount of timing before any hint of KR, was tuned for towing and 87 octane.

I thought a log I took yesterday (first one for this vehicle), was showing false knock, and of course it's a tad too large to attach here, so this morning, took another log, halfway to work, with 87 octane, then filled (1/2 tank to fill), with 93 octane, to see if KR disappeared, or minimized.

If anything, it showed more often KR.

I bought the truck from the original, older owner, so highly doubt there's ever been any "tuning" done to it.

I just don't get why there is so much KR?

Can anyone shed any light, or point me in the right direction?

Not asking for a free tune. I just have never seen so much KR on a stock vehicle, and am hoping someone with more experience than I, can take a look and offer an opinion.

LOG 111111 is 87 octane

LOG 222222 is 93 octane (mixed w/half tank 87)

p.s.
Pay no attention to WIDEBAND reading. Just got the truck and wideband is showing it's DEFAULT, since it is not connected yet.

Looks pretty normal for a stock tune with 87 in it. Might also be burst knock too, as some of it occurs on transitions. None of it looks "real" as in normally real knock (the kind that does damage) will register as a stair step pattern. The first cycle will register, then repeat on a second cycle getting worse with each. Without correction, it would continue as knock won't "fix itself" without some help from the PCM. Your log shows blips, and nothing more than about 2 degrees, which can be expected just about everywhere with 87 octane in the tank.

Took a look at the second log, and it looks much more like real knock there. You have a few stair steps on that one. Try a full tank of 93 and see what that does to it, and it won't hurt to disable burst knock either. Also log your knock learn factor to see how far the PCM is going over to using the Low Octane table.

Many of the new 07 and 08 trucks I have logged that were stock on 87 octane rode the knock sensors hard. They are higher compression and more aggressive timing wise the the early 5.3s were. You can try reducing the timing to see if it goes away, or as Chopper recommended fill up with 93 and see what changes in the log.

The log I took yesterday, had as high as 6* KR.
Unfortunately, the log was slightly larger than it would allow me to upload onto here or LS1tech.

I just added Knock Learn Factor and Burst Knock to be logged, and have to make an errand run here soon anyway, so will post back up the results

Quote:

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Originally Posted by charcoal03silvy

Many of the new 07 and 08 trucks I have logged that were stock on 87 octane rode the knock sensors hard. They are higher compression and more aggressive timing wise the the early 5.3s were. You can try reducing the timing to see if it goes away, or as Chopper recommended fill up with 93 and see what changes in the log.

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I have to go a little farther this morning, than I did on the 2nd log.

I'm also wondering about it being carbon build up, as a possible culprit? Previous owner was an older guy, and it was definitely a lot more of a turd, the other day, then it is now, as far as power. Feels like it's running stronger as I drive it more.

Here are the two best logs, that were allowed to be uploaded...

Both contain Burst Knock and Knock Learn on them.
I honestly am not knowledgeable on either, sadly...

The one showed 7.8 KR...

There is no audible detonation and as said, truck runs great.

The knock looks real for sure. It's showing the telltale "stair step" in many places. Check your advance histo, and you will see a lot of negative numbers because of this. It won't hurt to pull some timing off the high octane table. I also noticed your cylinder airmass isn't getting high enough to reach the lower end of the spark tables, so it's staying high pretty much everywhere in part throttle. Fueling looks good though according to your STFT's.

Looks like it just needs a bit of work on the spark tables, and some good fuel won't hurt either.

Quote:

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Originally Posted by ChopperDoc

The knock looks real for sure. It's showing the telltale "stair step" in many places. Check your advance histo, and you will see a lot of negative numbers because of this. It won't hurt to pull some timing off the high octane table. I also noticed your cylinder airmass isn't getting high enough to reach the lower end of the spark tables, so it's staying high pretty much everywhere in part throttle. Fueling looks good though according to your STFT's.

Looks like it just needs a bit of work on the spark tables, and some good fuel won't hurt either.

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Yes, I was a bit shocked to see negative numbers. Had never seen that before.

Someone suggested on another site that I may need to add a catch can due to known issue with these trucks sucking some oil into the intake...My 2002 never had an issue in over 200,000 miles and this one is at 63,000, but if it helps, and/or cures a problem before it starts, I'm all in.

Pretty much ALL new cars have that issue. The PCV system is straight garbage. It didn't dawn on me until I rebuilt my LS3 (for no particular reason) with about 30k on it. One day I noticed my intake was actually "leaking oil" (yes a freaking puddle under it) as it was just sitting there ON THE GROUND, removed from the engine. I investigated further and discovered that it was FULL of oil. I took a close look at the PCV system and realized it literally sucks oil into the intake right out of the crankcase, with no filter or anything else stopping oil mist from just flowing in there. It's part of all the emissions garbage out now days. I ordered a vacuum pump later that month. Worth it.

Yeah, the early GEN4 5.3s always show a lot of kr. Over 7 degrees is pushing it though. Hopefully that was in a low load situation. A decarbon might help a little. I have found that getting the VVE table right really helps them, not just kr but that too. Taking the timing all of the way down to eliminate the kr will make it much weaker and really hurt the milage. Some desensitize the knock sensors a little.

Adjustments to power enrichment settings could help too.

Raise the map kpa enable to 80, lower the pedal enable to 50-60%. Increase the enrichment ramp in from .0050 to 1.500. Try aiming for 12.0-12.3 commanded instead of mid 11's like stock does.

I do agree with removing burst knock too.

Thanks for all the ideas guys. I did notice that the DoD HO timing tables had a fair amount more advance than the "normal" HO timing table.

It seems to show most KR at barely any throttle at all.

How would I totally disable the Burst Knock Retard? I thought about turning off the DoD as a test, since it appears to happen a lot right when it goes into and out of V4 mode.

This thing is totally different than my old 2002 5.3 Silverado.

First thing I do is turn off the DOD. I am curious how much it will help your KR.

Quote:

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Originally Posted by IARLLC

First thing I do is turn off the DOD. I am curious how much it will help your KR.

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With nothing changed but Disabling of DoD, basically no change whatsoever.

I changed the PE settings to what 5FDP suggested above, and disabled Burst Knock Retard
(I zeroed out "Base vs. CylAir Delta because those numbers matched, exactly my degree of retard I was seeing) <---Hopefully that is correct???

I re-enabled DoD just to see what the results are.

The times I am seeing KR on the laptop (while driving), the truck is literally just off idle with barely any load at all.

I have to trailer my car to the dragstrip Saturday, so a good bit of the 87/93 octane mix will be gone. I sure hope this one doesn't REQUIRE 93 octane to eliminate KR, when my old beast of a truck was much more aggressively tuned and never got KR on 87...

I will log tomorrow and see what happens...

Thanks for replies so far. It's appreciated.

I just came to re-confirm that
A. carbon buildup could definitely be an issue (good suggestion) and is relatively easy to reduce over time using various techniques (use your favorite)

B. oil in the intake/pcv system troubles is also a high suspect. Oil raises compression ratio, contributes to knock. I would suggest you remove and thoroughly scrub the intake manifold then take steps to prevent future oil contamination (again use your favorite technique here, some use catch cans, some use vacuum pumps or different routes, upgrade pcv valves, my personal favorite is a combo of high performance PCV valve and if necessary an oil-return (back to the crankcase) system as opposed to a "can")

General steps are already mentioned:
1. try using higher octane fuels to compare where real and false knock is, i.e. if it knocks on 93 but not on 100 well there you go
2. reducing high octane timing maps in suspect regions is universal technique
3. faster enrichment, different enrichment settings can be played with
4. Compression test for general diagnostics (might find something unusual) TIPS: (write the numbers down! use a decimal place! use multiple compression testers! perform multiple tests!)

Final thoughts:
I generally tune my engines to NEVER show knock of any kind, on any fuel. That usually means tuning to the lowest octane you anticipate using.
If that means pulling timing or making modifications (lower compression, colder plugs, cooler intake air temp) whatever it takes...
And then I go back and test to make sure they still work by using worse gas or too much timing at light load to ensure they light up as a final test before 'forgetting about it'


last, I would not reduce knock sensitivity unless you've done the octane tests (1.) and timing tests (2.) and checked for oil contamination (B.) and done your best to remove carbon (A.)
And done a compression test (4.)

Because you certainly don't want it to ignore real knock.

i am going to follow this thread. i have a 05 with a bit more kr on 87 that you and more often. i did manage to blend some e85 and noticed a major decrease in kr ( down to a max of 2 deg and less often.

Any new news?

Quote:

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Originally Posted by Onomoto

Any new news?

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Installed a catch can, which is catching slight amounts of oil.
Cleaned intake and top-end, using SeaFoam Top Engine Cleaner.
Left BURST KNOCK RETARD and DoD TURNED OFF
These things did pretty much nothing for KR....
so....
Basically, started over, returned High & Low Octane tables to stock, and ran straight 93 octane premium unleaded...KR 100% gone

Decided that it would suck paying $.50 a gallon MORE for every fill-up, when truck is NOT a hot rod...but just a daily driver, part-time tow vehicle.

Turned on the FLEX FUEL option in the tune, and added a 1/2 tank of E-85....which as tested, showed 88-89% ethanol.

Truck ran great, best it has since getting it.
E-85 station is 4 miles away
$2.23/gallon
Get roughly 3 less MPG's, but performance and absence of any KR outweighs that IMO.
Not a fan of the so-called "Virtual Flex Fuel Sensor", and it also did NOT allow the "Flex Fuel Spark Adder" to add timing, like it should have.

Decided to buy the DSX Tuning Flex Fuel Sensor kit and have an actual optical sensor, to see and adjust fueling and timing, immediately.

Best $300 I've spent in a while....

Pleased enough, that I ended up converting my car, a street/strip 2000 TransAm, to full time straight factory style flex fuel setup, with inline sensor as well.
The sensor and an OS conversion allows timing and fueling changes made like factory, on that one as well...

:cheers:


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I have swapped plugs to a step cooler to hold the knock off.