97bowtie

iTrader: (1)

I'm trying to get my LTFTs slightly negative and I have a few questions. Here are the values of my current LTFTs:

Cell 1: -1.6
Cell 4: varies from -2.3 to +0.8
Cell 5: varies from +2.3 to +4.7
Cell 8: +0.8
Cell 9: +9
Cell 12: B1 +9.4 B2 +7.8
Cell 13: Varies from +2 to +5

I multiplied the whole IFR table by .92 to get these values. The question is, should I continue decreasing the IFR table values or start into the VE and MAF tables? If so, what should I be looking at changing in the VE and/or MAF tables? I'm pretty sure I want increase the MAF table values but I'm not sure which values affect a given cell. Looking for a little direction here.


My WOT LTFTs are B1 +5.5, B2 +2.3 and my O2 voltages at WOT are B1 899.89 and B2 900.43.


Any help is appreciated.

jimmyblue

iTrader: (11)

The LTFTs vary, I believe, because the fuel trim cells
(FTCs) on the F-bodies are nuts. Cells 0, 4, 8, 12 are
forced to trim 0-2500RPM operation. That's idle to
highway, across a region where the basis of airflow
measurement it swinging from speed density to MAF
based, the motor VE is changing, etc. If your LTFTs
are not stable then that makes it a bit difficult to
tune.

Cells 1, 5, 9, 13 are 2500-6502RPM and the other 8
of the closed loop cells are "out of play".

Using RPM boundaries that more finely divide the
region where you are actually closed loop, will
make each cell cover a less-changing area and do
a better, more stable job of it. Having Cell 0 only
have to do with idle, means you can tune idle in
just by a couple of cell values in the VE table.
Same, a little broader, for cruise etc.

If your fuel system is stock then put the IFR table
back to stock, you may get a result that looks like
it works but you're just embedding a lie into the
system. I think it's the VE table, coupled with more
FTCs in play at finer resolution, that will put you
right.

jimmyblue

iTrader: (11)

The LTFTs vary, I believe, because the fuel trim cells
(FTCs) on the F-bodies are nuts. Cells 0, 4, 8, 12 are
forced to trim 0-2500RPM operation. That's idle to
highway, across a region where the basis of airflow
measurement it swinging from speed density to MAF
based, the motor VE is changing, etc. If your LTFTs
are not stable then that makes it a bit difficult to
tune.

Cells 1, 5, 9, 13 are 2500-6502RPM and the other 8
of the closed loop cells are "out of play".

Using RPM boundaries that more finely divide the
region where you are actually closed loop, will
make each cell cover a less-changing area and do
a better, more stable job of it. Having Cell 0 only
have to do with idle, means you can tune idle in
just by a couple of cell values in the VE table.
Same, a little broader, for cruise etc.

If your fuel system is stock then put the IFR table
back to stock, you may get a result that looks like
it works but you're just embedding a lie into the
system. I think it's the VE table, coupled with more
FTCs in play at finer resolution, that will put you
right.

Also keep an eye on your O2s at idle, looking for any
sign of them "dropping out" occasionally; this puts
bad feedback into the trims and will push them
positive when they don't really need to be.