What is a good value for cell 21? What AFR should I see on the WB in decel (but not during DFCO)?

With my 98 F-body and using the stock VE I have -8% LTFT in cell 21 and an AFR of about 13:1
This with a MAF curve that gives me +/- 2% LTFT on the other cells.

If I change the decel VE values (low MAP range) I can adjust cell 21 to +/- 2%. AFR still remains 13:1 (?)

There is a big differece between the C5 (97-98 years) VE table and that one of the 98 F-body.
The C5 has about 20% less VE values than the F-body: this could explain why you see +8 with stock VE values and I see -8

So back to my question: should I see about 0% in cell 21? Does it matter?

From a functional standpoint on decel the PCM would turn fuel learn OFF and reduce or turn off injector pulse width to conserve fuel.
No need to be commanding fuel when the engine is in decel right so if you think about it there still is air flowing but fuel is shut down so end result is decel cells should be showing lean

Its a don't care since fuel learn is off thus those cells averages are not added to LTFT total.
When back on gas pedal, tip-in, PCM would be in another cell so a total decel, cell 21 would have no effect on on gas pedal cell

In some cars with lots of changes I have seen cell 21 go as much as 25 % lean but it does not trigger a lean DTC because again decel cells are not factored into cells when fuel learn is on

I was sent a PCM flash file from one of the dumbshits on that LS1tech forum had so called custom performance tuned.

They spout all about how a engine must have the VE table jerked arounf with

I almost puked in seeing what they did to this VE table



No wonder these morons blew up engines.

I put back the stock VE values on the Rebel



and sure enough with a testrun the car ran just fine even with all the engine mods using the stock VE table values

Retuning with my methods and using the STOCK VE table values a testrun proves trusting GM as to leaving the VE table alone gives the best overall functioning engine and best HP and Tq
Notice those values from past tests above when VE was screwed with

The idle cells, even on a stock-cam car, can be
easily corrupted by aftermarket exhaust cooling
the O2s. Particularly if you see a big positive
trim, and you see lazy / asymmetric O2 switching,
you may be dealing with mis-trimming more than
mis-reported airflow.

At decel you may be getting up against the min
injector pulse width limit setting, an easy thing
to determine from the logs (less simple, is what
the min PW to shoot fuel -really- is, for a given
injector, voltage and pressure).

A lot of people just dislike the MAF but it (and
the MAP sensor) are pretty well built instruments
at least until you whip out the die grinder and
mess the calibration up.

I have never felt the urge to get rid of the MAF,
although I did change it out for the bigger truck
piece along with a nice truck table. No worries.
But that's just my case, it -is- possible to get
bias errors with inlet tract airflow oddities and
you can see this by the plethora of GM tables, all
slightly different, used for the same Delphi piece
in different platforms.

A lot of folks seem to fixate on one thing and not
determine whether they are "fixing" the real actor
or just patching a symptom by roundabout means.
The tools do not replace diagnostic skills or an
understanding of the machine (which we all have
to acquire, however we can).