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Unread 05-12-2013, 01:53 AM   #12
Rich Z
Internet Sanitation Engineer
 
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Join Date: Mar 2006
Location: Crawfordville, FL
Posts: 15,123
Name : Rich Zuchowski
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Got some better results today by modifying table B4307 (Desired Airflow). I copied the table from a much earlier tune into my current working tune and reducing the values in the ECT (engine coolant temps) regions of 90 degrees and above by 10 percent. I also increased the airflow 10 percent in the lower ECT cells. Idle RPMs dropped down to a much better 925 to 950 rpm when I would take the transmission out of gear to coast to a dead stop.

I made some of these changes while out on a drive to log data, so I need to do a cold start up in the morning to see how everything reacts to a gas pedal blip. I made other changes to this same table last night, and noticed that the recovery time after blipping the gas pedal was greatly reduced. Went from 18 seconds to just 2 seconds. So that told me that I am likely on the right trail.

My guess is that the changes I had made to this table a while back were allowing too much air at idle, and when I would blip the gas pedal, the airflow and timing were fighting each other trying to keep the engine from stalling. Another obvious sign was that the RPMs were revving too high coming to a dead stop, which apparently was being caused by the throttle blade being open too much because of the commands from that B4307 table.

Just guessing, but I'll know more with more trial and error testing.
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