Looking at a datalog of entering PE.

Before entering INT is at 129 and BLM at 129. Once in PE I see INT immediately goes to 128 amd BLM stays 129. As the RPM and MAP changes during PE does the INT change from feedback from NB02? Is the BLM locked? Is the INT value shown while in PE of any value to determine fueling?

I am trying to get a handle on the VE tables in those areas I seldom venture unless there is a PE event. I believe in those areas my VE table is likely too high(rich). I understand when engine enters PE and looks back at last BLM, If <128 is uses that value, if >128 I recall it uses 128 to keep on safe side.

 

The INT goes to 128 as it is ignored in PE mode. Being a short term fuel trim this is actually a good thing. It is a reset to 128 whenever the ECM is in PE mode.

If the BLM is less then 128 it is ignored in PE mode (128 is used, which is neutral).

If the BLM is greater then or equal to 128 in PE mode it is used at the current value (adds fuel).

This is true for most GM ECMs. Although some will also lock the INT at the current setting upon entering PE mode and use it too. Which is not a good thing.

RBob.

 

Quote: If the BLM is greater then or equal to 128 in PE mode it is used at the current value (adds fuel).

Well i had the concept right, uses BLM that was adding fuel!

So the INT-BLM shown in logs are of no use in determining whether my VE table, where litttle correction has ever occurred, is accurrate. I did WOT this AM and I can see the AE at 11.0(was 9.8) and then it went PE to around 12.3 so it appears I am close. Engine felt good, rich no burble that I had prior, and it moved along nicely.

 

Sorry to bring this thread back, but I have a question dealing with PE in the EBL.

Are there no PE specific fuel tables in the EBLs programming? Do I just work the upper VE table to get WOT close and then let the VE learn do the rest? I've only done 5 or 6 VE learns so far and the idle and cruise are already getting very close to done, but the heavy throttle seems to be a bit lean at the moment. I want to manually add some fuel so that I don't go too lean.

 

There is the PE mode commanded AFR table. This changes the commanded AFR from what ever it currently is, such as 14.7 in closed loop, to a richer value for more power.

Then adjust the VE table to have the reported AFR match the commanded AFR.

RBob.