Do I need an Air Flow Meter?

[Bernd Felsche]

Bruce Plecan tapped away at the keyboard with:
> > >> You mention that I would probably need a sensor for
> > >> barometric  pressure, air temp, and RPM.  The stock AirFlow
> > >> Meter doesn't have any of this.
> > > Doesn't have to, it's figuring mass

> > Just picking a nit, but the Bosch "flapper-type" airflow meters
> > (as the original poster was asking about) do have an air
> > temperature sensor built into them, and provide it along with
> > the flapper position.  The later "hot-wire" type of airflow
> > meters are themselves temperature sensitive, so ambient
> > temperature is accounted for automatically,

> It still is calculating MASS, which was the point.  For proper
> tuning you need an air temp timing correction, IMO..

And mixture adjustment as fuel vapourization varies with inlet
temperature.

The flap-type meter is not a mass meter; it's a air momentum meter.
(i.e. mass * velocity) Air mass is then usually calculated by the
ECU with the aid of an on-board barometric pressure transducer.
That's the reason why many Bosch ECU boxes have an air vent.

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