PE fuel error, or somethin else?

[steveo]

ran into a weird thing today.

i've decided to target a 12.9-13 AFR in power enrichment, which is considered a 'safe' range for max power by pretty much everyone that tunes aluminum headed LT1s.

i got it really damn close, but i noticed average around 3200-3600rpm was swinging a bit rich, 12.5 or so.

i reduced the RPM AFR corrections by hex 0x01 @ 3200 and 0x02 @ 3600. this is less than 1% correction. i figure even if i overshot the mark, i'd be happy with a 13.1 or 13.2 average.

i left the other cells alone.

i matted it up a hill, and it broke right up after 3500 rpm, and wouldn't get over 4500rpm (it acted like it was on fuel cut).

reviewing the logs i found this was due to a lean condition.

here's a static analysis of my average AFR (ignore the low rpm stuff, i use PE for open loop idle):

**** Wideband AFR (Average) vs RPM during PE ACTIVE ****

RPM    0 -  400        0.0    0 Counts
RPM  400 -  800       13.9    2562 Counts
RPM  800 - 1200       14.4    191 Counts
RPM 1200 - 1600       14.1    1 Counts
RPM 1600 - 2000       15.2    1 Counts
RPM 2000 - 2400       12.9    6 Counts
RPM 2400 - 2800       12.8    20 Counts
RPM 2800 - 3200       13.0    21 Counts
RPM 3200 - 3600       12.9    47 Counts
RPM 3600 - 4000       14.0    26 Counts
RPM 4000 - 4400       15.9    22 Counts
RPM 4400 - 4800       17.9    11 Counts
RPM 4800 - 5200        0.0    0 Counts
RPM 5200 - 5600        0.0    0 Counts
RPM 5600 - 6000        0.0    0 Counts
RPM 6000 - 6400        0.0    0 Counts
RPM 6400 - 6800        0.0    0 Counts

obviously it went completely lean.

now i'm not discounting the possible coincidence that my fuel pump died, or my ign coil might have finally flunked it, and i haven't put a fuel pressure gauge on it yet... but it ran perfectly well yesterday.

isn't it a f#*^ed up coincidence that the RPM that it started flaking out at is exactly in the range i just tweaked the AFR table? is it possible this is some kind of math error in the bin? i can't imagine why though...

[EagleMark]

Did you change it back and try it?

[steveo]

i will tomorrow on the way to work, and try to find a place to open it up.

[RobertISaar]

shouldn't have effected anything from 4000-up though, the cells you modified would have been completely out of their range of interpolation.

[steveo]

well it wasn't the tune;

i tried to reproduce the problem this morning, it didn't break up on me at all, but it seemed to be lacking some power for sure, and it seemed to be stuck at max KR as soon as i floored it.

looks like i'll keep hunting, dont know whats going on