5.3L KR during data logging

[iCryWheniGoPoop]

Its hard to say what the issue was with the Truck that your service guy is talking about, There are so many "tuners" running around that just throw 5* of timing at the High Octane table, copy the High Octane table to the Low Octane table and then rape the PE tables (WOT) without a wide band, I almost feel sorry for the people that try to save $100 by going to them. For instance... I had an 03 Z06 Vette come to me 3 weeks ago that had 8*-12* of KR all through his WOT and running 13.8-14.0 AFR. The first time he took me for a ride to show me what it runs like, it started missing because a plug failed when the tip melted off. He told me that he just got it dyno tuned at a local tuner about 2 months ago and it never seemed right since so who knows about that truck after it had been tuned.

 

I'm not convinced these trucks are on the ragged edge of tuning. I honestly think there is a lot to be gained in VE tuning and cam timing along with dialing in the MAF scaling after the install of a well designed CAI and Exhaust. After the Air/Fuel tuning is dialed in, I bet some timing will be freed up.

 

 

As far as my KR goes... Its consistent as temps warm up. I don't see much of anything in the AM, just on the way home when it 50*+. Right now I am running half 87 and Half E85 (scanner shows 43% alcohol to be exact) so I have been focusing more on how the truck reacts to different levels of Alcohol. I did throw a Burst Knock filter in there and quickly realized that is not the issue, but it seems like there is some correlation with the knock and DOD on my truck. When I get a little more time I will set up my scanner to focus more on KR but I'm not going to sweat it though, The ECU is doing its job by pulling out the timing, its just aggravating to watch it do it when I know I can fix it but I'm too scared/poor to give up my warranty at this point.

 

If you can get more info on the dead 6.2 like year, miles and who tuned if possible, that would be helpful.

[CAtaylor]

Sounds good, hopefully you can nail it down. Mine doesn't seem to be related to the DOD, that was the first thing I though of when I saw it. I put it in 5M "no DOD" and it was still pretty consistent as well as on the interstate where mine will rarely try to go into 4 cyl mode. The truck that had the issue he said was a new 6.2L. I have to go by there to pick up some parts when I get in so I will see if the guy told him what tuner it was. Like I mentioned in the other post I don't know this first hand, this is just what the service manager told me. Chances are he was just one of the unlucky ones that had an engine issue and it just happened to be tuned when it crapped out.

[iCryWheniGoPoop]

Unfortunate for the owner either way, but I'd bet you are right.

[iCryWheniGoPoop]

Ok... after I posted last night it started eating at me. The temps were around 45* and I was still logging a lot of KR, over 1500 hits in 20 miles (that's based off of scan resolution so not as much KR as it sounds). 97%+ of my KR is when it goes into DOD and it will hit for 4-6 seconds every time it goes in. If I wasn't monitoring the DOD you would never know it because it just looks like it is popping up while cruising down the highway, but what made me think it was DOD this whole time was because I would notice a load change in my MAP sensor without any TPS change or RPM change, and now that I logged the DOD status bit, I have confirmed it. The remainder of the KR was only during transitions like downshifting then 3/4 throttle. I got 0* KR under WOT from a dead stop but if I rolled into it at Highway speeds, I would get 1-4*. So.. to sum it all up, the KR issues in my instance are all very tunable and will show improvement when they are resolved with a good tune.

[CAtaylor]

Maybe that is the case. I am unable to log the DOD status on mine with the provided EFI config file, it could be "thinking" about going into V-4 and I would not be able to see it. I did go back and look at my logs but I couldn't see any difference in the MAP sensor readings at the occurrences of the KR, everything looks to be stable during the cruising sections that I can tell or know to look at. I don't have the knowledge or tools to look at the stop and go sections to see if there could be a correlation some where. To me all it looks like is a bunch of trends and I really don't know what to look at to tell if it is related to something else. If I have enough time off when I get home I plan on having my gears installed. This should change the loading on the engine considerably and I will see if it has any changes on what I am seeing.

 

iCry: Thanks for all of the feedback on this. The knowledge is very helpful

[Mutau95]

Sounds good, hopefully you can nail it down. Mine doesn't seem to be related to the DOD, that was the first thing I though of when I saw it. I put it in 5M "no DOD" and it was still pretty consistent as well as on the interstate where mine will rarely try to go into 4 cyl mode. The truck that had the issue he said was a new 6.2L. I have to go by there to pick up some parts when I get in so I will see if the guy told him what tuner it was. Like I mentioned in the other post I don't know this first hand, this is just what the service manager told me. Chances are he was just one of the unlucky ones that had an engine issue and it just happened to be tuned when it crapped out.

When you go back to the dealer see if the truck is still there and have him point it out to you. Shop guys get so use to telling stories that it could be total BS or even something he heard. Or for that matter ask another tech walking around I'm sure if there has been a new 55k truck through the bay with a damaged engine.......every tech would hear about it if true.

[iCryWheniGoPoop]

After a long run of E85 tuning and logging I am now back on gasoline and have noticed quite a bit of KR. I would say that half my 22 mile drive had KR Friday on the way home from work.

[CAtaylor]

After a long run of E85 tuning and logging I am now back on gasoline and have noticed quite a bit of KR. I would say that half my 22 mile drive had KR Friday on the way home from work.

Are you concerned with it? I am sure it is something you are going to try and correct but do you think it is enough to cause problems down the road. Mine decreased a little after the BB tune but it is still there.

[iCryWheniGoPoop]

Are you concerned with it? I am sure it is something you are going to try and correct but do you think it is enough to cause problems down the road. Mine decreased a little after the BB tune but it is still there.

I am concerned somewhat, the ECU is doing it's job pulling the timing but what if the knock sensors fail or loose sensitivity, then it's just a matter of time. My amount of KR is small enough that 91octane would fix it easily but the truck is advertised at 87octane. What makes it worse is it only does it at cruise, light throttle and damn near all the time in that area If I pull a hill or accelerate from a stop, WOT... no KR. It's easy enough to tune out but I'm going to try different grades of fuel to see if it subsides.

I'm curious if Justin pulled some cruise timing out of yours in order fix it. I'm not interested in running 91octane but I can sure see these 5.3's running better on higher octane. At lease during the summer as temps go up.

 

I'm on a full tank now so it will be a few days before I report back with what different fuel does but I will let everyone know what I find. I do know that these truck love more timing on the E85 ;)

[CAtaylor]

I am really not sure what he did. I am running a 87-89 octane tune on 89 so it is probably conservative. I do see the KR during the same scenarios you mentioned above but not to the extent it was before. I plan on doing some more logging and will compare the before and after timing during cruise. I have about 350 miles of highway coming up tomorrow so I will update.

[iCryWheniGoPoop]

Yeah.. Check it out. I get it under some cruise conditions and real light acceleration.

[14'SilveradoLT]

I checked mine with TQ Pro the other day when running premium and saw a max of like 3* and that was a short time. After that tank went to about 1/8th I re-filled with 89 and picked a much more constant 2-3*.

 

I didn't really notice any on WOT...actually some negative.

 

I also noticed that my highway mileage dropped to 21mpg from ~23 mpg. But I ran slightly slower overall... it seems like the truck likes 67ish. Still working on that.

[CAtaylor]

Yep, it is still there, none at a 55 mph cruise though now. It is actually running more timing now but I am not sure if this is in the tune or due to the engine load being decreased with the 4.56 gears. The Logs I ran initially were with the 3.42's so it's not really apples to apples. If I pull the tune out I will do another log so I have something better to compare with.

[CAtaylor]

The left chart is after the tune and gear change the right chart is before running 35" tires with no computer adjustments. The white numbers in the cart are the mean / averages. Both were running 89 octane. You can see on the left one that there is more timing / less load and less KR. Like I mentioned I will pull the tune and see what it looks like with just the gears so I will have a good base to go off of.

 

Edit: 89 Octane not 98. Dyslexia kicked in.

[Jon A]

Personally guys, I would not feel comfortable running that much KR. I know the knock sensors are pretty good these days, but that's just not right. I'd run premium or back off the timing. In setting up my timing table (premium only tune), I'm not allowing it to have KR anywhere. In some spots, I'm running less advance than the factory map.

 

Interestingly, the 5.3 runs a lot more timing than the 6.2 does stock. More than you'd think they could get away with for having only .5 less compression and running regular at the same time, so it's not all that surprising to me.

 

The Corvette 6.2 also runs more timing in most areas than the truck 6.2 though with the different intake you'd expect different timing maps. Anyway, quite a few users have reported KR on those as well with stock tunes--even on premium. In those cases tuners are making more power by backing off the timing and getting rid of the KR. That goes to show how a good tune can make more power and actually improve longevity at the same time.