burst knock

[smslyguy]

I have the v.e table dialed in and the m.a.f. sensor is re-calibrated and yet i still have burst knock. I zeroed out b6210, but while scanning i notice on the data log that it is usaually pegged at 8.1. I even loaded a stock tune and the burst knock is still there, I thought once you had the v.e. tables dialed in it would eliminate the burst knock. Just to get an understanding on it, do you get burst knock from the calc air vrs the actaul air from being off?
My v.e tables are within + or -1 and the ma.f is the same. Just trying to figure out why. It is not affecting drivability at all just trying to understand it a bit more. Thanks for any reply's. Oh the car is in my sig. just basic bolt ons

[WeathermanShawn]

I have the v.e table dialed in and the m.a.f. sensor is re-calibrated and yet i still have burst knock. I zeroed out b6210, but while scanning i notice on the data log that it is usaually pegged at 8.1. I even loaded a stock tune and the burst knock is still there, I thought once you had the v.e. tables dialed in it would eliminate the burst knock. Just to get an understanding on it, do you get burst knock from the calc air vrs the actaul air from being off?
My v.e tables are within + or -1 and the ma.f is the same. Just trying to figure out why. It is not affecting drivability at all just trying to understand it a bit more. Thanks for any reply's. Oh the car is in my sig. just basic bolt ons

I usually make Table B6212 all Zero's. That will eliminate it.

First off, are you 100% sure its burst knock? Burst Knock has no real relationship with the VE Tables and/or MAF. It is a preventative pulling of timing when a large change in cylinder air mass is detected. I.E., you mash the throttle.

Smslyguy, not everyone agrees with this approach, but I don't like 'enabling' burst knock on a lightly-modified car. If your Spark Tables are dialed in, and you do not get any detectable KR (big difference from burst KR), then zeroing out Table B6212 will do the trick.

Hope that helps..

[joecar]

Post some files.

[N0DIH]

Greg Banish talked about Burst Knock in his first book, grab it and read it. He said it is a phenomon. It is something that needs to be there, you aren't going to get around it as easy as a simple tune, if that was all that is needed GM would just tune the vehicles to eliminate it. WeathermanShawn speaks the truth there.

My LT1 had it, and no way to deal with it. My L67 has tables for it, but factory turned off, but the non SC 3800's have it dialed in and use it. Diff? Higher compression.

Just thoughts...

[joecar]

I have the v.e table dialed in and the m.a.f. sensor is re-calibrated and yet i still have burst knock. I zeroed out b6210, but while scanning i notice on the data log that it is usaually pegged at 8.1. I even loaded a stock tune and the burst knock is still there, I thought once you had the v.e. tables dialed in it would eliminate the burst knock. Just to get an understanding on it, do you get burst knock from the calc air vrs the actaul air from being off?
My v.e tables are within + or -1 and the ma.f is the same. Just trying to figure out why. It is not affecting drivability at all just trying to understand it a bit more. Thanks for any reply's. Oh the car is in my sig. just basic bolt onsThe description for table B6210 says:
When a change in cylinder air mass exceeds these calibrated values, burst knock can be enabled.My understanding is this:

if B6210 is zero, then any change in cylinder airmass always exceed zero... so this would keep burst knock always enabled (as I understand it).

Instead, zero table B6212 so that when burst knock enables, zero timing will be pulled.

And burst knock retard does not show up in the KR pid... BKR has its own pid: GM.EST_KRB_DMA.

[WeathermanShawn]

Greg Banish talked about Burst Knock in his first book, grab it and read it. He said it is a phenomon. It is something that needs to be there, you aren't going to get around it as easy as a simple tune, if that was all that is needed GM would just tune the vehicles to eliminate it. WeathermanShawn speaks the truth there.

My LT1 had it, and no way to deal with it. My L67 has tables for it, but factory turned off, but the non SC 3800's have it dialed in and use it. Diff? Higher compression.

Just thoughts...

Just to clarify. If you ramp down High-Octane Spark fast enough from lower cylinder air to high in your tune, then in essence you have 'tuned' out the need for burst knock.

For example, I have ran the following High-Octane Spark table on a 11.0:1 CR, with no KR and no burst knock.

I like Joe's idea where you simply put the amount of Burst Knock to zero. Again, you have to have a 'perfect' High-Octane Spark Table. Otherwise, it may just be smarter to leave it 'enabled'. Problem is a any TPS mash may unnecessarily enable it. At least in in this OS, you can mitigate its effect. You just have to work on eliminating any mechanically-induced KR.

Good luck..

[smslyguy]

yes shawn, this is exactly what i did. I was just woundering what causes burst knock or if it is of any concern. I know it it burst knock and not "real" knock and that it is not pulling any timming off anymore since i zeroed out b6210. Just trying to understand as to the "why's" i would be still having burst knock. It shows on the scan that it it constant at any throttle. It did it as well on my stock tune??

[smslyguy]

The description for table B6210 says:My understanding is this:

if B6210 is zero, then any change in cylinder airmass always exceed zero... so this would keep burst knock always enabled (as I understand it).

Instead, zero table B6212 so that when burst knock enables, zero timing will be pulled.

And burst knock retard does not show up in the KR pid... BKR has its own pid: GM.EST_KRB_DMA.

yes joecar i am logging that pid GM.EST_KRB_DMA for burst knock only. I did however just zero out b3610 and not b3612 and that did infact elimenate all my burst knock. Just a thought it worked on my car??

[WeathermanShawn]

yes joecar i am logging that pid GM.EST_KRB_DMA for burst knock only. I did however just zero out b3610 and not b3612 and that did infact elimenate all my burst knock. Just a thought it worked on my car??

Just for clarification smslyguy. You said you zeroed out B3610? What OS are you running? On mine that is a PE Delay RPM Bypass. Is that what you meant?

Thanks..

[joecar]

The difference between BKR and faster octane scaler ramping is that BKR tries predict if knock will occur and avoid it, whereas the faster octane scaler ramping is after the fact...

Exactly what N0DIH said, knock may or may not occur on a load increase, but GM thought critically enough about it to add extra code/tables to try to avoid it.

Some people can get away with zero BKR, others can't, depends on their engine and conditions.

:)

[joecar]

...
I zeroed out b6210, but while scanning i notice on the data log that it is usaually pegged at 8.1.
...
yes joecar i am logging that pid GM.EST_KRB_DMA for burst knock only. I did however just zero out b3610 and not b3612 and that did infact elimenate all my burst knock. Just a thought it worked on my car??We're not following...:doh2:

[WeathermanShawn]

Small..

I would be interested to see your original BRK log. Got it that it was probably a typo on your last post.

What I do not understand is that in your first post you stated that 'zeroing' out that Table made no difference. Now it does? It is confusing that your would have BRK constantly?

For all those following the thread. What Joecar and others have stated make sense. I reviewed some of my WOT logs. It takes me less than 1/2 second to go from .24 g/cyl to .72 g/cyl. BRK would have probably done the same thing as manually ramping down the spark amount. One reason I eliminated it to keep my spark additions & subtractions to a minimum. It is part of my tuning philosophy on keeping it simple. But, I agree it many cases it may be best to 'leave it alone'. It does have a purpose. In my case I can only tolerate 22-25 of spark at WOT, so ramping down served my tuning purpose(s).

Small, I would be curious on that log. It might help others who do not quite understand BRK..

[smslyguy]

here is a copy of my scan. As you can see on the scan data it is almost peged at 8.1 burst knock. After looking at that scan's spark tables and the actual spark tables it does appear to be pulling about 8.1 degrees of spark. Have a look let me know what you think? Thanks.

[WeathermanShawn]

Chris:

O.K., I see it is getting the KRB values from Table B6212. What values did you have in Table B6210 when you did this log?

To get it to read zero (0) KRB, the easy answer seems to manipulating B6212 to read all zero's. Are you saying you changed Table B6210 to all zero's and it worked?

[smslyguy]

yes i did change b6212 after reading your reply's on here and that fixed it. It was indeed still pulling timming before, but not anymore. My timming has advanced now almost 8.1 from before would this be enough to throw off my v.e tables and my m.a.f tables as well? I did re-run the open loop to see if my v.e. tables needed any adjusting and they were spot on. If anything a little rich. same as my m.a.f table.

And no b6210 did not work. It just wasn't registering as k.r. but was still infact pulling timming though. b6212 fixed that. Thanks for the reply's.

[WeathermanShawn]

O.K., I think I got it. Glad to hear you fixed the burst knock dilemma. Obviously, keep monitoring for any KR. Without the preventative action of KRB, you now have to be extra vigilant for KR.

Your VE and/or MAF Tables should not be thrown off to a great degree. The effect of reduced spark may cause a slight difference in AFR's, but running closed-loop you should be able to tell a difference in your LTFTBEN's. If you see the LTFT's really swing, then I would contemplate an airflow re-do. Personally, I would not worry about it too much as it applies to your tune.

The main thing is you do not have to drive around with a constant 8 degrees of timing being pulled. That had to be annoying.

Good luck..