computer project

[Roberto L. Landrau]

I am very interested in doing something similar to the project
described by Nigel on his message of 23 May 1995 (a computerized MPG
meter).  I was contemplating the idea of adding a flow meter to the
fuel line, but that causes a problem: not all of the fuel that goes
through the fuel filter is injected; some of it goes back to the
tank.  I would need two very accurate fuel sensors and take the
difference between the two.  This doesn't seem to be very practical.

I have the same inputs that Nigel mentioned (pulse train
proportional to speed and injector signals) except I don't know if I
can use the inujector pulse width to determine fuel flow.  With
constant fuel pressure, I presume the flow rate is proportional to
the pulse width, offset by the injector "dead" or "turn-on" time. 
The fuel pressure in my car varies as a fuction of vacuum (or intake
air pressure) level.  Would I have to add a fuel pressure sensor in
order to compute fuel flow?

In case it matters, the engine is a Mitsubishi 2.0l DOHC turbo and
the application is the 1st generation Eclipse/Talon/Laser family.

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Roberto L. Landrau	landrau at mitre.org