programming for a MAF based system

[Bruce]

MAF or MAP, neither do any direct reading of the *air*.
They both use sensors, and both have good and bad points.  Like any sensor,
it's a matter of it, various other sensors, and then the math to come up
with a PW.

MAF, hot wires, will always seem at a glance to be slower to read then MAP.
The wire will always have some mass to it and take a given time to respond
to change.  A sudden change in temp., and airflow will take a look at the
MAT for the ecm to refigure the correct timing and fuel.
HOWEVER,
the MAP is faster reacting to changes, but in this lays another problem, in
that it's overly sensitive, and needs more filtering then the MAF, so while
you can have a finer resolution AE/MAP correction then a AE/MAF, they both
take time to recalculate things.

In my own car, it is a MAF system, and it working very well.  I use a late
GM MAF so I have resolution to 500 gms/sec..  But, do to heat soaking of the
intercooler I just have to try MAP, and just see what works for me.
YMMV,
GM sensor, calibration specific
Bruce



From: "les" <lesd at earthlink.net>
> I was under the impression that the MAF sensors , because of the way the
> air molecules are being measured by the hot wire, already compensate for
the
> thin air encountered at altitude.
> Also, my whole reason of going to MAF instead of speed density was to
> avoid the whole VE mess. You need VE for a speed density system, because
it
> has no idea of the actual grams/sec air going into the motor. It only has
a
> 'guess' that when combined with the VE at a particular RPM results in a
more
> accurate air intake amount.
> I'd like to richen the mixture under boost, and I think I can do that
> based on the table that I would use for the MAF, with an rpm lookup.
> My system will run a turbo air-cooled VW engine, and for now I want to
> keep the ignition out of ECU, or maybe just provide an analog voltage to
> a Crane ignition system, to retard under load. Keeping it as simple as
> possible means that I would actually build it, and it would still be
> better than a carb, I would think :-)
> My biggest concern is that I don't know the output curve for the Bosch
> MAF I have. I can always get the engine running at idle by adjusting
> a rich-lean knob I would have as an analog input to the ECU, as a tuning
> aid. But I don't want to have to define the curve by a trial and error
> method, all the way up the curve, it's too tricky. maybe I can assume
> it's a hyperbolic curve, and start with that?
> -Les


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