flow bench using EFI parts?

[AJLegere at aol.com]

Tom,

I'm just picking up on this conversation but can offfer the following
guidance.  
Virtually all industrial instrumentation will operate on 12 Vdc. Many just
barely.  For the  most part if you use a 250 ohm resistor in series with the
unit connected to 12Vdc the unit will perform the function of restricting the
current between  4 and 20 mA.  This will provide the  range of 1- 5 Vdc drop
across the resistor representing 0-100 % of the calibrated range of the
instrument.  Rather than buying a new instrument there are a number of
companies that offer refurbished instruments for reasonable costs.  A new one
for a 30 "WC differential pressure transmitter costs around $1100.  
In terms of the flow; volumetric flow is a function of the square root of the
pressure drop across any known restriction.  Air temperature and static
pressure can have dramatic effects on the readings.  Formulas are readily
available from a number of sources.  Check for Miller, Shinsky or any Crane
catalog.
In past experimentation building a flow bench to port heads I used an orfice
of a known  bore versus pipe i.d. (beta) (try to keep this ratio around 70% as
the pressure recovery after the orfice drops of quite quickly when you drop
below 70%) and used the air temp, statiic pressure and pressure drop accross
the orfice to calculate flow.  It works well and is relatively simple to
construct using a powerful shop vac, orfice, temp gauge, and two  inclined
manometers (one static pressure and one pressure drop accross the orfice.    

Food for thought, 
AJL