This is classic JIM C. " your right , im wong " NOT

[mark kibort <mkibort@xxxxxxxxxxxxxx>]

Jim,
Please  why the insults.  I am telling you the facts of a AFM.  It does
measure mass flow
it has to .  Please help us all understand how in the world it can measur=
e
air speed (volume)

You said that you dont open your mouth unless you know the answer.  Pleas=
e
Please please, stop with
the attacks.   Just tell us plain and simple the reason the flapper valve=

moves  against the air flow.
Here are my direct questions so you can keep it clear.

1.  Your engine takes air volume  according to the displacement and RPM. =
  =

(forget about  pressure drops for a second and volumetric efficiency)    =

Wouldnt a 2.3 liter engine take about 225 cfm at 6000 rpm??

2.   the speed of this air going throught the engine can be calculated at=

any diameter .   =


3.    The AFM flapper valve moves do to differential pressure. (   Mass
Flow)  For the same flow rate , lets say at 6000 feet altitude
the air would be 20% less dense.    at the same air  VOLUME  flow   say
225cfm, would the flapper valve displace the same or  less than at sea
level   (THIS IS THE ONLY POINT)    PLEASE ANSWER.  BUT ONLY OPEN YOUR
MOUTH IF YOU KNOW THE ANSWER..    =


So yes or no, would the flapper valve move more or less for the same air
flow rate , or volume at altitude? .   =


4.   Ill give you the hint again.   at altitude , the air is less dense. =
  =

the engine would still be taking 225 cfm at a  lower atomospheric
pressure..RIGHT??  So, if so , the 225 cfm with the molecules of air
farther apart would create less of a pressure differental on the flapper
valve and move it less , Right??    (ie, more flapper valve deflection,
more fuel injector deflection)

5.  Yes, there are barometric and temp sensors , but they all help make f=
or
a more accurate sense of air density.
LH jetronic (mass flow also) will have temp sensors as well.  This
information may be used to change timing to prevent pinging at Higher
temps.
Im not the expert with this systems , you seem to be.   Im only trying to=

help you understand as Bosch has even said in their books, AFM measures
mass, but at a efficiency cost.  (the neck down ,and neck back up creates=

losses or pressure drops that reduce HP due to , yep you got it, less den=
se
air.)




Message text written by Jim Conforti  (MY comments along side his with th=
e
>>>>>>>>)
> No Mark.. it doesn't...
it measures air VOLUME FLOW..
  The Temperature corrections and Baro corrections are specific
  to AIR DENSITY.. =

<
 I think you really never thought this one through

 Yeah.. you're right.. and I and all the engineers at =

 Robert Bosch are WRONG.. =

>>>>>>>>>>>>>>>>>>>>>>>the engineers at bosch  would agree with this
concept.
they call it an air flow meter but it actually measures mass flow, and ve=
ry
well.    Not as acurate as
a Hot wire system ( MAF)  but still very good at measuring mass flow.  =


 Mark.. what you haven't figured out is that I don't open my mouth
 unless I KNOW the answer. =

>>>>>>>>>>>>>>>>>>>>>>>>Ok, I think you never will admit if you dont.  th=
at
makes you dangerous to =

this list as well as a great asset.   Think, THINK.  the AFM will not and=

can not measure speed of the air.  the speed of the air
is the same at any RPM.  this means that at 6000 rpm there is the same
speed of air moving pass the AFM, just less dense.
What part of this dont you understand.   this is now becoming silly.    I=

have enough experience in this area to =

say that it is true and you are making a false statement.   Just talk to =
a
Aero engineer about my point .   They will agree with me.



> If Im wrong, well, I will owe you a million "im sorry's"    That is why=

> airplanes go so fast at altitude   speed over the sensing devices are
> saying 200mph, but your going 500mph ground speed.  =


  Because of DENSITY?!?  We don't have any Pitot tubes in the AFM last
  time I looked.. =

>>>>>>>>>>>>>>>>>>YES <It is  because of density!!!!!.   the Pitot tubes
are getting less pressure built up in  them and indicate
 a speed relative to pressure.    .  you see the air at 30,000 feet is ve=
ry
thin  because of this
to keep same amount of  mass flowng over the air frame the plain can go
twice as fast relative to the ground at the same indicated speed at sea
level.  this is why in aviation you have indicated and true air speed. =

(BECAUSE OF DENSITY)

> Point being that  on an engine your speed is fixed to the displacement
and
> the rpm.   so, air speed stays the same at a given RPM =


  It does.. Hmm.. I guess I can throw all those predictive equations of =

  cylinder and manifold filling away now.. Quick, I'll get McLaren on
  the phone to tell them your discovery.
>>>>>>>>>>>>>>Dont be a smart ass.    Do you not agree that an engine
generally takes a certain volume of air
at a certain RPM   (ie a 2.3 liter takes 250cfm at 6000 rpm whether you a=
re
at 7000 feet or sealevel)  =


  As far as pressure differentials.. they don't always affect flow rates
  (hint: remember about CRITICAL flows.. and pressure ratios)

>>>>>>>>>>>>>>>>>>>>  your right , they dont , they effect air density
(that has been my point all along!).  Now we are talking (arguing in
circles)  pressure differentials will lower density thru  the engine.   (=
ie
pressure drops along a engine air path may be 1 or 2 psi depending on the=

restriction.  remove these and gain density and HP)  =


  Suggestion: Put down the AERO texts.. and pick up something pertinent
  like John B. Heywoods Internal Combustion Engines. (around $90) =

>>>>>>>>>>>>>>>I havent even cracked a book for this discussion.  =

Obviously you haven't either . Do yourself a favor
open a encyclopedia and look up how planes fly.

>>>>>>>>>>>>>>>>Let me make a suggestion to you .  YOU obviously understa=
nd
what you are doing.  You  are arguing
with me just to argue.  Face it , the afm is a pressure or Mass flow mete=
r
enven though not officially called such.  (it truely is a pressure device=
,
but mass flow is directly proportionate , and intimately dependant on air=

density.)
Our readers should keep one thing in mind from this discussion.   An air
flow meter measures Mass flow plain and simple.
as the molecules of air hit  the flat plate, a pressure is built up in
front of it. it moves to the differential of pressure from front side to
rear.   If the air is less dense, but moving at the same speed (as it wou=
ld
at altitude), i would move proportionately  less.   Basic law of
theromodynamics   PV=3DNRT    YOU shouldnt need to have a barametric sens=
or
with a pressure device, or mass flow device
Bosch  may have had other reasons for it.    anyway,   One last question.=


WILL AIR MOVING PASS THE AFM AT THE SAME SPEED BUT LESS DENSE, MOVE THE
FLAPPER VALVE MORE OR LESS?

IF YOU ANSWER IS YES, THEN IT IS A MASS FLOW DEVICE.   (crude, but
effective)
IF YOUR ANSWER IS NO, THEN YOU DONT UNDERSTAND THE FLOW DYNAMICS, PERIOD.=

(OR at least cannot articulate it)

Mark Kibort
www.electricsupercharger.com
(where people have too much fun with their cars)

------------------------------