afm as a mass flow device.

[mark kibort <mkibort@xxxxxxxxxxxxxx>]

Message text written by INTERNET:bmw@domain.elided
>he job of the conditioner that converts the MAF signal to a AFM-like =

signal seems pretty easy.  Remembering the ideal gas law from freshman
chemistry:

   PV =3D nRT

Where P =3D pressure, V =3D volume, n =3D # of moles, T =3D temp, R is a
constant.

The MAF measure the mass of the air (per unit time), while the AFM
measures volume of air (per unit time).  Since the mass of air is
proportional to n we get:

   V =3D (mass) * (some_constant) * T / P

>>>>>>>>>>>>>>Ive been thinking about this also , but I have to disagree =
on
the comparison of a MAF to a AFM as being that different. Ive measured th=
e
voltage of the AFM at sea level and at altitude and it is much differnt a=
t
any given RPM at full throttle.
This makes sense because as a 2.5 liter E30 takes in 250 cfm at 6000 rpm,=

the air will be less dense and the flapper valve will deflect against the=

spring less.    It also deflects less on a hot day vs a cold morning as I=

have tested.   This is a mass flow device by design.   Not a great one, b=
ut
one none the less.  This means it is detecting the amout of mass being
drawn pass it.     Obviosly , the temp  change in the hot wire , mixed wi=
th
barmometric and temp inputs is much more efficient, and less restrictive
too.

you basically get rid of the neck down  area of the AFM as it is only abo=
ut
4 square inches, but if that is the size of one intake valve, (only one i=
s
open at any given time, then the neck down , may  not effect flow ,beside=
s
the obvious turbulent flow due the the ugly shape of the flapper and
opening itself.

the AFM is shown to support HPs in the 400 range =









So far, it sounds like what the "conditioner" does is pretty simple.
The _Roundel_ article also mentions that the "conditioner" also =

dampens the response of the system, to avoid stability problems.
This is also pretty easy.  Just throw a cap in parallel to the
MAF, right?  (Ok, I admit it... I am a CS major, not an EE.)

A circuit that does this sounds pretty simple, but I think it is
going to involve op-amps... this pretty much pushes the envelope
as far as my knowledge of electronics goes.
<

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