re
Since it's the AFM doing this and not the ECU, a MAF device would
need to simulate the effect in some way, by monitoring rate-of-change
of the airflow and increasing the signal to the ECU when there's a
rapid increase in flow.

Systems with an air mass meter have a more evolved throttle switch ..
in the case of Subaru ..
3 wires ...and it's more than just 'idle' or 'wot' info to the ecu as on a
waterboxer.

the 3 wire TPS can sense Rate of Change of throttle opening I believe, and
this is how the ecu knows when to richen up for acceleration ( akin to accel
pump on carb engine ) .

rather fascinating,

----- Original Message -----
From: "David Beierl" <dbeierl@ATTGLOBAL.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Monday, December 06, 2010 9:21 PM
Subject: Re: MAF Sensors and the Vanagon

> At 11:07 PM 12/6/2010, Larry Alofs wrote:
>>David,
>>    Please clarify.  Are you saying that the mechanical inertia of the
>>vane is a good or a bad thing  Do you feel that the programming of the
>>ECU takes this inertia into account?
>
> I'm saying it's a good thing and corresponds to the accelerator pump
> in a carburetor.  When you open the throttle quickly, the air flow
> increases very rapidly and the inertia of the vane, which is fairly
> substantial, causes it to overswing somewhat.  This tells the ECU
> that there's more air going through the system than actually is,
> causing it to inject extra fuel, hence for that short interval a
> richer mixture.
>
> Since it's the AFM doing this and not the ECU, a MAF device would
> need to simulate the effect in some way, by monitoring rate-of-change
> of the airflow and increasing the signal to the ECU when there's a
> rapid increase in flow.
>
> Yrs,
> d