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False Knock?

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Old 02-27-2013 | 05:50 PM
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Originally Posted by MikeGyver
I am pretty sure that if the ECM is commanding EGR, then it is using the EGR spark table. Maybe the EGR valve is stuck shut? If it is, the lack of exhaust gas in the air/fuel mix would cause detonation.
My guess is that the ECM was not commanding EGR since there was one or more EGR codes.

Not sure how to test the EGR valve, but I've logged some of the other EGR PIDS (with the EGR valve installed) and it seems to be functioning. I currently do not have any EGR codes either.

I'm going to pull some more timing from the problem area tonight and log on the way home. I'll post the log and tune.
Old 02-27-2013 | 05:51 PM
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Just disable it and get it out of the equation.
Old 02-27-2013 | 05:59 PM
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Originally Posted by GMCtrk
Just disable it and get it out of the equation.
Need it for smog at the moment
Old 02-27-2013 | 07:27 PM
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Originally Posted by Ferocity02
My guess is that the ECM was not commanding EGR since there was one or more EGR codes.

Not sure how to test the EGR valve, but I've logged some of the other EGR PIDS (with the EGR valve installed) and it seems to be functioning. I currently do not have any EGR codes either.

I'm going to pull some more timing from the problem area tonight and log on the way home. I'll post the log and tune.
You should be able to test the EGR in the scan tool side of the soft ware. With the engine running, command the EGR on and the engine should die.

Originally Posted by Ferocity02
Need it for smog at the moment
As long as it's physically there, that is all you need. Mine is Physically there but is disabled in the tune and it passes every time!

The EGR doesn't even come on when they dyno test it any way.

It also runs cleaner since I disabled it in the tune.

Last edited by 1FastBrick; 02-27-2013 at 07:35 PM.
Old 02-27-2013 | 07:34 PM
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Originally Posted by 1FastBrick
As long as it's physically there, that is all you need. Mine is Physically there but is disabled in the tune and it passes every time!

The EGR doesn't even come on when they dyno test it any way.

It also runs cleaner since I disabled it in the tune.
Good point! Somewhere I read that the EGR can help with fuel economy. I may just disable it in this tune and zero out the EGR spark table.

If I disable it in the tune, will the throw any codes?
Old 02-27-2013 | 07:36 PM
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Originally Posted by Ferocity02
Good point! Somewhere I read that the EGR can help with fuel economy. I may just disable it in this tune and zero out the EGR spark table.

If I disable it in the tune, will the throw any codes?
Yes it will, You will need to set the codes to not report and I believe you have to disable The EGR function.

I added how to check the EGR in the previous post.
Old 02-27-2013 | 07:41 PM
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Sending you a PM
Old 02-27-2013 | 09:54 PM
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Here is my tune and log from driving home from work. I pulled 4-5 more degrees from the problem area and it didn't help much. While on the highway you can see I was getting into the throttle to try to get KR. For tomorrow's drive to work I'm going to disable EGR and zero the EGR spark table to see if that helps.
Attached Files
File Type: tun
tune1.tun (476.2 KB, 123 views)
File Type: efi
Log_0019.efi (169.5 KB, 174 views)
Old 02-27-2013 | 10:37 PM
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First off let me start by saying I am in no way shape or forum a Professional tuner.

I am curious as to why is your Spark Low Octane Table is so high in such a low RPM from .003 to .007???

I wonder if this is were your Knock is coming in???

Also curious, Did you have some one give you a base tune or did you modify this on your own from stock or from another tune you found on line??? Feel free to PM if you don't want to post up the info in public.
Old 02-28-2013 | 12:50 AM
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Originally Posted by 1FastBrick
First off let me start by saying I am in no way shape or forum a Professional tuner.

I am curious as to why is your Spark Low Octane Table is so high in such a low RPM from .003 to .007???

I wonder if this is were your Knock is coming in???

Also curious, Did you have some one give you a base tune or did you modify this on your own from stock or from another tune you found on line??? Feel free to PM if you don't want to post up the info in public.
Currently, the low octane spark table is the same as the high octane table, with 10 deg taken off the entire table. I was under the impression that the high octane table will always be used unless there is knock in which case it will start using more of the low octane table via the adaptive spark scalar. The stock low octane table for the most part is higher than mine.

The tune was a mail order from a sponsor. They tweaked the spark tables, but I have slowly been adjusting the high octane table to mitigate knock retard. I also have been making other minor adjustments (fans, gears, DFCO, idle, rev limiter, etc) none of which have had an impact on the knock.

Probably need to do the Auto VE before I mess with spark anymore. I'm waiting to get the turbo kit on with the wideband before doing that though.


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