MAP sensors

[dn]

> Was wondering if anyone tried to use MAP sensors and Bernollies equation to
> determine Mass Airflow.  I'm thinking if one had three MAP sensors (one for

Mike:

Dodge used to use a system similar  to  this  in  their  earlier  fuel
injection systems.   Don't  know  if  they  still use it or not.  As I
recall, though, they used vanes in the inlet to create a vortex in the
airflow sensor, and a couple of pitot tubes to measure the pressure at
the center  of  the  vortex.  Was a little more complicated than that,
somehow they relied on the vortex "whipping" around in  the  tube  and
measured the  frequency  of the resulting pressure pulses.  I got this
from a book called:

Domestic Electronic Fuel Injection and Computer Systems
by Frederick D. Allen
Prentice Hall
ISBN 0-13-218256-4 

This  book  is  worthwhile  reading,  although it doesn't go into much
detail on the electronics side, it describes fuel injection systems in
general from the Big 3 and is a good overall reference.

As far as using a venturi or  the  like,  the  pressure  differentials
involved are  very small and difficult to measure.  I think you'd need
an accurate (read "Expensive") differential pressure sensor to do  it,
along with  temp  comp, etc.  I don't think the stock MAP sensor would
be sensitive enough for the pressures involved. May be do-able but not
easy or cheap.  If the Big 3 don't do it, it ain't cost effective!

Regards
dn



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