Is 2 degrees of Knock Retard common on a stock LS3 camaro tune?

[justhereforinfo]

2011 ls3 camaro 34k miles. Only modification are 2 inch headers and 3 inch exhaust, no cats. The only tuning I've done so far is removed TM, bumped the fan % vs ECT, disabld cags, and turned off codes for the 02s. All timing and fuel settings are stock, and I'm seeing some KR. Some at part throttle, some at redline. Up to 2 degrees at 6000 rpms. I'm not so concerned with the part throttle stuff, but KR at redline worries me. Unfortunately, I never logged the car before the exhaust modifications, and dont have a wideband yet. I would think that the stock computer could compensate enough fuel to cover the additional airflow from the aftermarket exhaust, but I'll bow to your better knowledge if you tell me differently.

With this stock timing tune, I'm seeing up to 26 degrees of timing and the car pulls great, especially up top.

Would you be concerned?

m5.hpl

[schpenxel]

Doesn't look bad to me, it appears to always occur right as you're starting to push the throttle towards WOT so you might have a cell or two you could reduce to get rid of it

Keep in mind that everything after the initial KR is just the retard decaying off and is not actually knock, just in case you decide to make any changes to the timing table.. you don't typically need to change everything that shows up in a graph/histogram of KR but rather just around the points where the KR originally occured

[bigdaddy9185]

2011 ls3 camaro 34k miles. Only modification are 2 inch headers and 3 inch exhaust, no cats. The only tuning I've done so far is removed TM, bumped the fan % vs ECT, disabld cags, and turned off codes for the 02s. All timing and fuel settings are stock, and I'm seeing some KR. Some at part throttle, some at redline. Up to 2 degrees at 6000 rpms. I'm not so concerned with the part throttle stuff, but KR at redline worries me. Unfortunately, I never logged the car before the exhaust modifications, and dont have a wideband yet. I would think that the stock computer could compensate enough fuel to cover the additional airflow from the aftermarket exhaust, but I'll bow to your better knowledge if you tell me differently.

With this stock timing tune, I'm seeing up to 26 degrees of timing and the car pulls great, especially up top.

Would you be concerned?

m5.hpl

Sounds to me that the knock is being caused by a lean condition . You put headers on and now the engine is breathing easier , I would look at the logs where it is knocking and then referance the short and long term trims to see how much fuel is being added or taken away may need to riches the map in the areas where you have knock . Have you returned or tuned your MAF yet if not that needs to be done and then your VVE needs to be done as well

[bigdaddy9185]

Also ls3 generally like about 22-24 max you have other adders that could cause you to end up with more timing than needed

[tbrtuning]

The two degrees is only occurring when first getting on it and transitioning to power enrichment. Adjusting your power enrichment settings might help. At 8:23 in the log is a good example of this. Remove the power enrichment delay and increase the enrichment ramp in to something like 1.00 or even 2.00. I'm not sure what's best there. You can also lower when the enrichment will begin with the PE Throttle/Pedal table.

[NJ_Phil]

I think there are 2 problems, both minor and saw them both after doing the headers on my car. (2012 LS3)

The small KR bumps at low loads are either caused by the headers or timing a few degrees too high. They show up only above 30* and closed loop (not PE). Throw a can of Torco in it. If they go away, it's too much timing, still there it's the headers. Regardless which one it is, lowering timing will get rid of it if you chose to do that. I just live with it cause it ain't real and don't worry if < 1% in closed loop.

The KR during transition into PE is probably burst knock because it comes in fast and decays gradually. Its caused by going from 20% to 100% pedal in 100 milliseconds, neither the MAF or computer can react this fast and the ECM is protecting the motor by adding burst knock. I'm a poster child for smashing the throttle down instantly but it does no good. The physics of the motor react the same whether you put the pedal down in 200ms or 20ms so doing it so fast only triggers the burst knock protection. I slowed down the throttle rate opening to 10% so it opens at a slower rate regardless of how fast it gets stomped and got rid of the burst knock

[justhereforinfo]

Doesn't look bad to me, it appears to always occur right as you're starting to push the throttle towards WOT so you might have a cell or two you could reduce to get rid of it

Keep in mind that everything after the initial KR is just the retard decaying off and is not actually knock, just in case you decide to make any changes to the timing table.. you don't typically need to change everything that shows up in a graph/histogram of KR but rather just around the points where the KR originally occured

Good tip, thanks.

[justhereforinfo]

Sounds to me that the knock is being caused by a lean condition . You put headers on and now the engine is breathing easier , I would look at the logs where it is knocking and then referance the short and long term trims to see how much fuel is being added or taken away may need to riches the map in the areas where you have knock . Have you returned or tuned your MAF yet if not that needs to be done and then your VVE needs to be done as well

Also ls3 generally like about 22-24 max you have other adders that could cause you to end up with more timing than needed

I have not touched the maf or VVE yet. Intake filter and piping will be next to change, so I dont feel like doing it twice. The lt and st fuel trims in the knock areas are usually zero'd out, since im in PE. but even outside of PE, they are less than %2.0.

[justhereforinfo]

The two degrees is only occurring when first getting on it and transitioning to power enrichment. Adjusting your power enrichment settings might help. At 8:23 in the log is a good example of this. Remove the power enrichment delay and increase the enrichment ramp in to something like 1.00 or even 2.00. I'm not sure what's best there. You can also lower when the enrichment will begin with the PE Throttle/Pedal table.

Makes sense. I've increased the PE enrichment rate to 1.0, but left the delay at 5,000. Report back.

Na, why delay PE, i zerod the delay.

[justhereforinfo]

How can I setup my scanner to see which of the other tables are adding the additional timing? Hi octane only commands 20, and Im getting 26 based on other parameters, like afr and iat, ect. Any way to add channels to see whos adding what?

[schpenxel]

Add everything to your channels list that you can find that has the word "advance" in it. That should cover about everything, IAT, AFR, etc.

[justhereforinfo]

I think there are 2 problems, both minor and saw them both after doing the headers on my car. (2012 LS3)

The small KR bumps at low loads are either caused by the headers or timing a few degrees too high. They show up only above 30* and closed loop (not PE). Throw a can of Torco in it. If they go away, it's too much timing, still there it's the headers. Regardless which one it is, lowering timing will get rid of it if you chose to do that. I just live with it cause it ain't real and don't worry if < 1% in closed loop.

The KR during transition into PE is probably burst knock because it comes in fast and decays gradually. Its caused by going from 20% to 100% pedal in 100 milliseconds, neither the MAF or computer can react this fast and the ECM is protecting the motor by adding burst knock. I'm a poster child for smashing the throttle down instantly but it does no good. The physics of the motor react the same whether you put the pedal down in 200ms or 20ms so doing it so fast only triggers the burst knock protection. I slowed down the throttle rate opening to 10% so it opens at a slower rate regardless of how fast it gets stomped and got rid of the burst knock

Thats good to know about the headers. I kinda had a feeling it may be false knock. There are literally thousands of people who just slap headers and exhaust on their camaros, drive the piss out of them for years and never log a second. I pulled one degree from the problem areas as shcnitzel (lol) suggested to be safe, and quickened the PE response. But thats about as far as ill get into it. Car runs great, its fine. seems to be the norm.

[justhereforinfo]

Add everything to your channels list that you can find that has the word "advance" in it. That should cover about everything, IAT, AFR, etc.

Thank you Sir! I see you have a very useful link in your sig. Thanks for that also.

[NJ_Phil]

"shcnitzel (lol)" I gave up on trying to spell that a while ago and just call him Carson, one of the most helpful guys around.

[chassis]

High Five for Schpenxel (Carson)!! Great guy and willing to help those who need it.....

[schpenxel]

The number of people that know me by name around here is starting to weird me out! lol jk

[chassis]

Who said Stalking wasn't fun.

[justhereforinfo]

update: So i quickened PE's response time to 1.0, pulled 1 degree from the common trouble spots. Now I only have 1 degree of KR or less in those same spots.

Coincidentally, the trouble spot is also exactly right where I usually mash the gas. I'm guess the timing table doesnt need adjusting, but a faster PE. I've upped it to 1.0200. we'll see.

I also ran into a 2016 camaro ss automatic with an axle back. You can see in the log where i bumped the limiter in second, but somehow I still managed to nose him out at the top of third before letting off. I thought they ran 12.20's stock...

2016ss atuo run.hpl

[schpenxel]

1 to 1.02 won't really make any difference, 1 is already plenty high. The GM trucks that actually make use of the delay are set to like .002 or something crazy low like that, once you get into numbers around 1 it's pretty much instant

Could also be some of the transient knock sensor settings, I haven't checked those out but I had to bump those up a little on mine