C6 LS3 A6 Surging Idle

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08-19-2009
JoeyJoeJoe

C6 LS3 A6 Surging Idle

I am tuning a 2008 C6 LS3 A6 w/ G6X3 cam, LT Headers, CAI, and 2800 Stall. The car starts and idles cold fine. Once it is warmed up, if it is idling for a min or two it will start to surge a lot. It will sometimes get so bad that the car cannot correct and will stall unless you give pedal assistance. I noticed that the spark was jumping all over the place when it was surging. I don't have a good long idle log, but do have a scan I did while out driving. The spark is doing the same thing on decel/light cruise, but worse than idle. Any help would be appreciated.

I dont have the WB hooked up on the scanner.

I am running 2.23 Beta
08-22-2009
JoeyJoeJoe

Trying to make sense of this

I am trying figure out exactly what is happening on this car. I made a config to log all the spark I could find that seemed relevant, plus some that probably were not. I was also logged Dynamic Airflow and the Default MAF (SAE) I noticed these #s were close but never the same at the same time. which/if either is a representation of actual Airflow into the motor and which is from the MAF Calibration.

After a few little changes to spark(Set HO, LO, and Base Idle to 23 in idle area) and Base Running Airflow(added 4g/sec 2 at a time, up to 1200 rpm) started the car, it started without pedal assistance, reved itself to about 2k and came down very slowly to set idle. After 30 secs or so it started surging again,(scan log frames 300-1000) I reved it off idle for a few seconds then let it idle, and it sat and idled fine, turned ac on, still idled fine, put in gear, idled fine. Turned car off and let sit. Re started and did the same surging after about 10-30 secs of run time. After reving it up a little seems to be fine. The car drives fine, and have no issues on the street, just dont like that the idle is pick when you first start it. There has to be a way to fix it. I am not looking for hand outs, just some one to point me in the right direction. I have read tons of idle setting procedures here, but after trying most, I am still coming to the same result. Any thing would be greatly appreciated.
08-22-2009
LSX378

Quote:

Originally Posted by JoeyJoeJoe

I am trying figure out exactly what is happening on this car. I made a config to log all the spark I could find that seemed relevant, plus some that probably were not. I was also logged Dynamic Airflow and the Default MAF (SAE) I noticed these #s were close but never the same at the same time.

which/if either is a representation of actual Airflow into the motor and which is from the MAF Calibration.

SAE MAF is the actual airflow. Dynamic Airflow, or SD MAF, is calculated from the GM calibrated airflow model (VE) and MAP/RPM etc.

Gotta love chasing idle challenges. :)
08-24-2009
JoeyJoeJoe

Actual airflow being the airflow based off of the MAF calibration I did? And Dynamic being the uncorrected based on the VE table that I am not quite sure I can even attempt to calibrate(this car has a vitural VE, I am pretty sure)?
08-25-2009
LSX378

Quote:

Originally Posted by JoeyJoeJoe

Actual airflow being the airflow based off of the MAF calibration I did? And Dynamic being the uncorrected based on the VE table that I am not quite sure I can even attempt to calibrate(this car has a vitural VE, I am pretty sure)?

Yes the C6 with E38 has coefficient based VE modelling. Search for Bluecat on this forum. There is a VE tool.

Yes MAF = actual from MAF table. Dynamic = VE table/map/rpm/etc. You might call it a virtual MAF :D.

Have you tried going back to stock and starting all over again?
08-25-2009
JoeyJoeJoe

Quote:

Originally Posted by LSX378

Yes the C6 with E38 has coefficient based VE modelling. Search for Bluecat on this forum. There is a VE tool.

Yes MAF = actual from MAF table. Dynamic = VE table/map/rpm/etc. You might call it a virtual MAF :D.

Have you tried going back to stock and starting all over again?

I went back to stock for the idle airflow, adaptive and spark over/underspeed error. Logged MAF g/sec vs my airflow final minimum table. Got the car to idle in as many of the cells as I could via Scanner Controls, changed AFM table in Park/N for those cells, found my percent error for those cells and tried to continue the trend for the rest of the cells. Repeat for in gear. The car idles pretty nicely now, the under/overspeed spark is going nuts keeping it steady, but when it tries to surge now, the computer corrects before it gets going to far. Before I had crazy spark and surging, now I just have crazy spark, but dont know if I can do much about that with this cam and an auto.

I was thinking of adding a filter to the histo so that I would only capture data under decel, idle. that way I could drive the car around and get a much more accurate picture of Actual Airflow Minimum.