Quote from bosch book, Jim have you read this? AFM is a mass flow device.

[mark kibort <mkibort@xxxxxxxxxxxxxx>]

To Jim and others concerned:

Right from the Bosch book of Automotive Fuel Injection Systems Technical
Guide.  =


PAGE98 =

" Unlike D-jetronic, however, the L-jetronic system relies on mass air fl=
ow
metering as teh main input variable to determine the amount of fuel to be=

injected)    ( D jetronic is the MAP system for metering fuel based on
Pressure sensors in the TB or Manifold)

PAGE 100
" The relationship between mass airflow and the angle of the flap was
chosen so that the precentage error is kept constant over the full oerati=
on
range of the engine."

Page 100
"The relationship between the mass airflow and  the flap angle is
logarithmic, which ensures a non linear characteristic in the
potentiometer."

Page 103
"The air flow  meter in L-Jetronic provides a highly accurate measure of
the actual mass of air entering a particular engine under any combination=

of speed and load."

For jims comments of why the barometric pressure input: =


they go on to  say that the barometer  input was added to provide even mo=
re
precise adjustment to air flow  to meet california emissions.    =


So , yes,  the AFM is a Mass flow device .  Pressure measured at the fron=
t
of the flapper valve is directly proportionate to mass flow, however, JIM=

you are righ in one way.   In an extreme case of less dense air say at
10,000 feet, in an engine compartment
that is hot, the 2nd order equation relating to the momentum of the air
will also be a factor that needs to be adressed as this becomes more of a=

factor after 10,000 feet, but perfectly fine and as the book says  " No
practical significance at 7000 feet".

Others posted agreement that at altitude that the flapper valve would not=

be displaced for the same flow rate.  One guy even posted that thru his
formula, that equal pressures could be reached for different densities. =

THIS WAS GOOD EXCEPT HE FORGOT TO CATCH ONE FACTOR IN HIS FORMULA, =

SPEED!!!!!!!!!!!!!    Yes, the speed in feet per second was higher. provi=
ng
the point that at the higher speed equal mass can flow.  This is not the
Point.  At 6000 rpm, the same volume will flow to the engine at almost an=
y
altitude (and will vary with RPM).   the differerence is the DENSITY OF T=
HE
AIR.   =


So Jim was this you who said.  " Dont pay any attention to the guy behind=

the curtain, I AM THE WISARD OF OZ !!"

 Look, all of my discussions have be about getting the facts right.  Peop=
le
need to get out the books sometimes and understand what is really going o=
n.
 =


Now I have the books you suggested out.   Ive quoted a noted author who w=
as
giving the above information from:
Bendix , holder of many patents of the AFM   Robert Hoge and Dan Barnard
Bosch AG    Frank breitsprecher and Eckhard Noelte
Daimler Benz      peter viererbl and Bernd Harling
BMW      michael schimplke and Dirk H. Strassl

Who is right you , or these guys above?????????????   DONT KILL THE
MESSENGER!

Mark Kibot
(www.electricsupercharger.com)




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