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When I was going over to Breton Bay today to take the 'Launch Area' pictures, I did some testing. I wish I had a data logger to capture what happened.

I did a series of 3rd gear accels (1500 to 6000 rpm) to get a better feel of how much power is being made and when. This car has 4500 miles and has not been modified. The first 3 runs were all about the same and uneventful. On the 4th run, at around 4500 rpm, there was a minor hesitation then a power burst up to 6000 + rpm. After the event it ran better than ever. I have seen this hesitation on different cars just after peak torque on the chassis dyno when the engine was running rich. I had never held this thing wide open that long before. I have to think there is some PCM learning going on here but all the experts say 'NO' not at WOT.
 

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Perhaps you blew out some carbon, maybe you should do that more often. :D I know I do. :lol:
 

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I find this commonly on my car(02) especially when I have had the car sitting up for a while (couple weeks) w/out driving.

After a couple passes through the gears at 6000 rpm 1-2-3-letting off in 4th the car seems fine. I don't know if the injectors are loading up or what but when the car does as you mentioned it nevers misses just hesitates then takes off.

Sorta reminds me of a cold engine effect even though the engine is at operating temp.

:guiness:
 

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Hi there,
As explained in the other post, WOT is a fixed value, and cannot be changed, nor learned. The fact of what you felt could have been anything, as the only positive way to determine if there was a difference, would be obtaining snapshots from everyrun, and looking at the data.
You would look for Powerenrichment on or off. MAP readings, knock sensor retard data, stability of the MAF readings, and other issues, as the o2 and LTFT, and STFT will default to 0.
NO 2 acceleration runs are ever the same, at all, in any way. Something always changes, and in these changes, could be your answer.
Besttoyou, c4c5:eek2:
 

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Roger,

You raise a very good question. I have heard two statements about this topic which seem to be contradictory. (1) The PCM ignores the O2 sensors at WOT. It just takes the LTFT from the cell just before you went to LTFT, "enriches" it to get to about 900 MV (about 12.4:1 AFR), and stays there. (2) But then why does cell 22 (WOT) have a LTFT value, if it ingores the O2 sensors? Cell 22 definitely has a LTFT value, I've measured it on my car. This doesn't make sense.

I have a good book I'm reading: "Corvette Fuel INjection and Electronic Engine Management" by Charles O. Probst (available from Amazon.com). He explains a lot of the PCM functions in this book, but some of the nitty-gritty details are not there. In particular, exactly how the long term and short term fuel trim tables work and what each cell corresponds to are not listed. I'm wondering if this is "GM secret" stuff?

I have yet to see a complete explanation of the algorithms in the PCM, but I keep looking. If you find out more info, please post it.
 

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In response to my comment on the hesitation I've experienced, only happens at WOT in a sudden WOT situation in just one gear.
which gear it doesn't matter. Usually down shifing and going into WOT.

Never happens off the line from a dead stop, or from a roll and going to WOT in the same gear. Example, from a roll in 3rd downshifting into 2nd and hitting WOT. The car will hesitate
then take off w/out missing then go into other gears w/out hesitation.

Seems like a electronic sensing value has to be (made) accepted then the circuit accepts the WOT value. Just guessing.

Whatever it is I noticed it and it just gives me more reasons to practice (or getting on it) running the car. I always shift at or about 6000 rpm to avoid the limiter and the car hauls ass just fine.

Interesting comments from previous treads. Anyone have any ideas when or where the 02 GM service manuals will get released?

Best to you all.:guiness:
 

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Roger, I don't have an answer to your question but here is some food for thought. One of the tricks when bracket raceing a computer controled car for consistance is to disconect the batt. every run to dump the computer learn. It works. If the computer learn has no efect on WOT, I wonder why it works. Ric
 

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PowerShifter said:
Roger, I don't have an answer to your question but here is some food for thought. One of the tricks when bracket raceing a computer controled car for consistance is to disconect the batt. every run to dump the computer learn. It works. If the computer learn has no efect on WOT, I wonder why it works. Ric
Do you practice this also? I noticed your times you post are awesome. :cheers:
 
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