Frank,
>You are right in that at WOT the fuel and ignition settings come from tables
>within the ECM (Open Loop). At WOT the mixture is rich for two reasons, to
>keep
>the Cat cool, and for power, emissions regs. are a lot more lenient at WOT.
>Additionally there are adaptive cells in the ECM to take up production
>tolerances
>between engines. What I want to do is push the mods right up to the point
>where the computer can't adjust (lean condition). If we still have room for
>improvement,
>then we can go to someone like JET for a custom chip that will richen the
>fuel. The computer actually looks at the O2 sensor(s) up to approx. 7/8
>throttle settings,
>most of the throttle settings will not be a problem.
Awesome job on the TB's!!! Count me in on the deal.
To really see what's happening with the ECM you'll need a
scan tool or a PC w/scanning software. There are a few OBDII
products that will scan CC vehicles. OBDTool offered by
CarComp http://www.carcomp.com comes to mind.
AutoXray makes a hand held unit but doesn't have an
OBDII compliant product yet, it's still in development.
I use an AutoXray scan tool on my '95 Impala SS (OBDI)
and it works great. You can really analyze what happens
when you make a component change. You would also
be able to possibly detect potential problems.
As for the ECM, the adaptive cells that you mentioned (PID loop(s))
are very forgiving for most changes. Since our system is speed
density, the ECM relies mainly on manifold pressure (MAP) and the
TPS to determine engine load/air volume. Making changes
to the TB, or, specifically, increasing airflow shouldn't be much
of a problem for the ECM. Keep in mind that the ECM is also
designed to handle such conditions as, a severely clogged
air filter, clogged fuel filter, etc.which forces the ECM to make
the corresponding corrections to the A/F, timing etc. for these
conditions.
What we will REALLY need is decent ECM tuning. Personally,
I feel something a little_stronger than a JET product is required.
I'm currently trying to get SuperChips in Orlando to develop
code for the late model 96-99 Dakota's/Durango's but they
are kinda backlogged at the moment. I have offered my Durango
as a test mule to use on their dyno.
I have worked with them in the past with my Impala, so we'll see
what happens. They offer chips for earlier Dakota's so, someone
may want to give 'em a jingle.
Mike Marx
'98 Durango
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