NicD

iTrader: (7)

OK, here we go with the question of the week with LS1 PCM's.

Does burst knock show up as knock retard using autotap or your favorite scanner? Burst knock is the timing the PCM will pull when it senses a large change in airflow very quickly to prevent knock. This doesn't mean it hears knock and pulls timing, it pulls timing to prevent it from occuring.

MSCLCAR

Maybe. I didn't know there was such a thing, but I think my car does it. Now that I have resolved my lean condition, the only KR I see is when I first go WOT, and a blip when it shifts.

emarkay

"A table that defines the Gms/Cyl change in Airflow to initiate
Burst knock, More commonly called Tip-in" taken from the LS1Edit update list.

I was not aware that that was a feature of F-body PCM's and am not up to speed on other applications. Will refer this to the expert on this topic. Stay tuned...

gojo

iTrader: (12)

On shifting I think your seeing Upshift Torque Reduction.
Regarding Burst Knock. If I start logging with EFI with only the key on, I will sometimes see a spark spike when I start the car. That may be one example?

emarkay

BTW, see here for data on Torque Management - the drivetrain protection system:
http://www.efilive.com/forum/viewtopic.php?t=314

Blip on ignition is prob a system voltage spike..... alternator field enable, pcm initialise, AIR pump drawing gobs of current.....

gojo

iTrader: (12)

Is that the case even if it shows up as knock retard?

Fetumpsh

Burst knock will "not" show up as 'real' knock retard in a scanner because knock never actually occurred, just look at your tables to know how much timing it will pull out and what parameters will allow burst knock to occur.

Fetumpsh

Oh, what do I win.

NicD

iTrader: (7)

Nothing yet. Tell me why as a test I deleted both knock sensors, yet when I would wack the gas in gear I would see knock retard then it would dwindle down quickly. What could possibly cause knock retard if both knock sensors are turned off? Do you have any proof or documentation for your "theory"?

gojo

iTrader: (12)

If that's so, what is the 3 degrees retard I'm seeing occassionally on start up?

Fetumpsh

You "deleted" them, do you mean you just unplugged them or disabled them in the calibrations?.

NicD

iTrader: (7)

Deleted as in deleted the code's for the sensors in the engine diagnostics. I am speculating that deleting the codes for the sensors will disable them entirely, same as every other sensor/code in the PCM. Not to mention I could sit there and rap on the head with a hammer prior to the code deletions and see knock retard activity but as soon as I deleted the codes I could register no knock with the hammer. Again, do you have any proof or documentation for your "theory"?

Fetumpsh

What's up with the smart **** attitude you have displayed the entire thread??.

These PCM's have a 'default' knock retard value if there is a problem with the ESC system (yes I know you disabled the knock codes from setting), but think of it like this, the EGR can be totally enabled/disabled right (LS1Edit - EGR Enable/Disable), and you can also turn off the EGR codes from settting.
So turn off EGR processing AND turn off EGR DTC's, get the picture...

You are turning off the ESC DTC's (read the line above again).

deezel

Another way to test whether you are seeing burst knock or real knock is to go into the PCM and change one of the sets of tables to zero. First, set all the burst KR tables to 0 and see if your KR still happens. Then, put burst KR back to stock and set all of the normal KR tables to zero....

This should tell you where your KR comes from.

Regarding timing spikes... remember that there is also an airflow spike at tip-in. If you look on the stock timing tables at low RPM and high airflow, the timing is quite a bit lower than in the power band. The timing dip you see at tip-in may just be the correct value from an unexpected place on the timing table (for example: 1.25 gms/cyl at 2000 RPM).
cheers

Fetumpsh

I assumed he would have done all that as part of the test??

NicD

iTrader: (7)

Because I want factual proof of something, not just somebody's best guess. It's not a smart *** attitude, sorry you see it that way.

Yea, it would pull 4 degrees of timing during power enrichment mode, which shows up as KR on a scanner. It doesn't do that anymore at WOT since the codes are disabled, just like it seems it turned off the knock sensors. I believe my test I described shows that by turning off the knock sensors codes it effectively disables the entire system by not showing any knock from a hammer rapping on the head. This was repeatable just to make sure it wasn't a coincidence. So what is this KR I am seeing sometimes when I blip the throttle quickly? It would appear at first glance to be burst knock pulling timing because I sure don't hear anything either. The next step would be to zero the tables of burst knock but I can't get it to reproduce exactly each time making the results of such a test not as exact. I would rather not try it that way and that is why I am asking this question to see if anybody knows this for a fact and if they have proof like something from a GM PCM manual, documentation, etc.

Bink

Staying tuned for emarkay's findings.......................

joel

Fetumpsh

Right, a tuning manual for the LS1 PCM, try here

Delphi Corporation
World and North American Headquarters
5725 Delphi Drive
Troy, Michigan 48098-2815
USA
Tel: [1] 248.813.2000

NicD

iTrader: (7)

Who asked for a tuning manual? Maybe you missed the post above yours where emarkay is getting information from somebody who might know for a fact if/how it is implemented, etc. That is all I was asking for and you never did say where you got your info from either, it was a simple question with no smart *** attitude implied. Again, sorry to challenge your knowledge.

emarkay

Still waiting, and please let's not act like fifth grade girls at recess......