5.3L KR during data logging

[CAtaylor]

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.

That is why is started the topic originally, the chart on the right was completely stock other than the tires. 95% of people will never look at what the engine is actually doing and they will run with that much KR the life of the vehicle. It is very surprising to me that GM let this out for production like that. I am sure there is redundancy in the system somewhere but if the sensor goes, with them pulling 10 deg of timing at places in stock form, you would think the engine will follow not long after.

[iCryWheniGoPoop]

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.

 

You are 100% correct, my concern is how every 5.3 is running these timing tables and I'm wondering if it could be the reason for the poor fuel economy in many of them. It's quite possible that they are running on the low octane timing table which would greatly effect fuel economy.

 

As far as the two trucks being close on compression but much more timing on the 5.3... It could all be in cam profile, and same with the vette. The cam profile in the 5.3 could be creating a lower dynamic compression in this engine which will be a little more forgiving with timing. 10.5 & 11 - 1 Static compression is only a part of the puzzle.

[14'SilveradoLT]

I posted in MPG's thread about my recent monitoring over a 'Short" distance using tq pro. I saw about 1-2 in KR swapping from 89 to 93. It's always been "MY" understanding that on a higher compression engine...1* of timing is up to 8whp. So if across the map I'm gaining ~10whp and getting about ~2-2.5 more mpg's....I'm all in.

 

Seeing that truck was still pulling like 2-3 (a few -1's and a lot more 2's under lighter load) everywhere throughout the 18 mile trip on 89....pretty much tells me that 87 will not be in my fuel tank anytime soon.

 

Edit: It seems that WOT the truck is pretty good no matter the octane...it's the moderate loads that really go screwy, but I need a lot more time watching and logging.

[Jon A]

 

You are 100% correct, my concern is how every 5.3 is running these timing tables and I'm wondering if it could be the reason for the poor fuel economy in many of them. It's quite possible that they are running on the low octane timing table which would greatly effect fuel economy.

 

Yes, it certainly would kill mileage. These things use a bunch of timing advance/cam retard at cruise for mileage/emissions/egr best compromise. KR is one of the first things somebody somebody getting crappy mileage should check for.

 

 

As far as the two trucks being close on compression but much more timing on the 5.3... It could all be in cam profile, and same with the vette. The cam profile in the 5.3 could be creating a lower dynamic compression in this engine which will be a little more forgiving with timing. 10.5 & 11 - 1 Static compression is only a part of the puzzle.

 

Yup, there are lots of variables and the cam is a big one. I don't know the specs on the 5.3 so it's hard to compare. The Vette and Truck 6.2's have the same cam, but of course with VVT the same cam can work quite differently depending upon how you time it. Most of the differences are at cruise though, they're timed pretty close to the same at WOT.

[14'SilveradoLT]

I used to be able to datalog with Livewire (SCT)...I've been using the TQ Pro app sparingly and "my" truck is liking premium fuel better. I see a lot less KR on light and moderate loads. I really can't see any real differences on WOT pulls, though.

[HondaHawkGT]

So what's the conclusion on the KR with the 5.3? I recently got my Black Bear tune and Justin found some detonation in my datalog with a 91 tune. I switched to his 89 tune and even with 91 octane fuel I'm seeing blips of KR. Nothing at WOT thankfully but still annoying. I even looked back at my stock datalog and I have a couple moments KR on 91 octane.

[gone_fishing]

So what's the conclusion on the KR with the 5.3? I recently got my Black Bear tune and Justin found some detonation in my datalog with a 91 tune. I switched to his 89 tune and even with 91 octane fuel I'm seeing blips of KR. Nothing at WOT thankfully but still annoying. I even looked back at my stock datalog and I have a couple moments KR on 91 octane.

 

Do you know if your "blips of KR" are showing up while in V4 mode? I can't log KR but I can view it through my ScanGauge II (along with timing advance). Cruising in V4 mode will always show some KR here and there. V8 cruising I don't see much if any at all. I have tried different gas grades and there is a difference between 87, 89, and 91 (87 of course being the worst). It's interesting to watch the relationship between the engine trying to run and maintain V4 mode and the timing advance. If timing advance starts to fall (because of KR) and ends up only being 4-6 degrees of advance, it switches back to V8. The higher the octane I run, the easy time it seems to have in staying in V4. What's really interesting is if I run E85, KR is basically gone and it will run in V4 mode a LOT more. Timing while in V4 can be upwards of 15-20 degrees advanced depending on loads (into/with wind, grade, speed). Long story short, the 5.3 likes higher octane levels!

[HondaHawkGT]

I have AFM disabled so I haven't seen any of that behavior. I did some research the last couple days and it sounds like the 4-5* KR blips I see are probably "knock learn". After getting my 91 tune from Justin and datalogging I had a couple 10-11* KR spurts but never at WOT. They occured after lifting off the throttle. I'm guessing the hot weather and possibly bad fuel had something to do with it. Sounds like I might have to reconsider E85 if I can't find better 91 octane gas -- 93 octane is nonexistant.