Here is a low cost fuel flow meter from Tracy Crook that should work
with just about any engine using four electronic injectors.
With minor modifications it can be used with any number of injectors.
I redid (cosmetically) Tracy's original schematic somewhat.
With his permission I will post it on the ACRE NL web site.

Paul Lamar

Will this work with subtracting the fuel in the return line?

AI Nut

Yes it will as all it does is measure the fuel coming out of the
injectors. Many car computers use this info to calculate the instant
and average MPG and display it on the instrument panel. My 1992 Dodge
Caravan has such a display.

Paul Lamar

Nice!  How does it handle the systems that vary fuel pressure?  Is there
enough difference in actual fuel delivered to matter?

AI Nut

It won't work with simple systems that vary fuel pressure regardless of intake
manifold vacuum. Some systems keep a constant pressure difference between
intake manifold and fuel rail pressure. In those systems it should work fine.

For systems that don't vary fuel pressure or keep a constant pressure difference 
it must be calibrated somehow. I have given calibration some thought for the 
last couple of days and the best way I can come up with is adjust it based 
on the fuel consumed on a cross country flight.

Paul Lamar
 
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