MAFs

[Bruce Plecan]

> I was wondering aloud what the advantages would be over a draw-through
> MAF, or a speed/density system.  The disadvantage appears to be potential
> contamination of the MAF itself.  I fail to see the advantages, beyond
> a bit more simplicity.  Simplicity can be a complete reason in itself,
> as well as pragmatic reasons that doing so allows you to assemble parts
> you already have into a working system.  Just wondering if there are
> any other reasons.

How about the shear fact that if the IAT compensation is internal to the
MAF, then the metering allows for heat saturation of the I/C.   For doing
things as correct as possible makes the tuning all the easier.   this way
just a MAT timing table would allow for perfect tuning, or close to it.
All the IAT and MAT sesnors I've tested are rather slow to respond.  This
eliminates that, at east for thair sensing.  Now an MAT can be used for
timing control.  Still would be slow, but beats having errors in both timing
and fuel.

> And by "fragile", I hardly meant mechanical strength, nor was I referring
> to any particular MAF sensor.  Most MAF sensors will not put up with
> anywhere near as much abuse as a solid-state MAP sensor.  If the late GM
> sensors do, then I'd say that's a welcome advance.

GM MAPs use a strain guage so there is a moving part, the late GM MAFs no
moving parts.   A moving part is perfect for failure.  With the way I did
mine (MAF mounting) it's isolated on both sides with hoses.   To mount a MAP
real close usually means mounting solid (as done by some oems).   Mounting a
strain guage where supbject to vibration is less then perfect.
Bruce

> james montebello

> On Mon, 5 Feb 2001, Bruce Plecan wrote:
> > If the turbo's seals are gone, then that is the problem, and needs
> > addressed.   New GM MAFs are true hot wires, and nothing in the air
stream
> > (but the wires, and a bridge to hold them),  I shot Carb cleaner on it
and
> > no ill effects.   The film ones are another matter and they most often
have
> > a film board in the air stream (also often have a plastic case).
> > Picking parts for the right useage, is key.
> > If your calling the late GM MAF fragile you need to take another look.
AL
> > housing, O-Ring seals, fully encapsulated, I couldn't dream of better.
> > In my application, the MAF allows SEFI,  so while I spend $50 more on
the
> > MAF sensor, it's well spent in my opinion.
> > FWIW, I'm actually doing this, not quessing about it.
> > Bruce

> > > Not just oil from the PCV, but oil from the turbo itself...
> > > I'd never even considered using a blow-through airflow meter
> > > configuration.  I suppose it would somewhat simplify the system, but
it
> > > seems you're trading off a set of cheap, robust sensors (MAP, crank
angle,
> > > and air temp) for a fragile, expensive one (MAF).
> > > james montebello

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