> I actually prefer to measure my fuel level based on how many
> miles I've done
> since last fill up.  And I've gotten really good at this based on
> how/where I
> know I've driven.

        Yes, I've used the same method, the results are quite accurate, especially
if filling up with the identical pump.

> I've looked into this as well in the past.  Flow sensors (for fuel) are
> ridiculously expensive, so this is the way to go.

        Plus, with flow sensors, I'd need two, one for the supply line, one for the
return line. Double ouch...

> > I guess if I had the diameter of
> > the injector port I could get a rough idea but I'm wondering if anyone
> > knows of a more accurate way (I doubt the relation is that linear
> > considering a mass is moving). Does GM publish the pulse width vs. gas
> > injected curves? Anybody ever see these curves. Maybe the ECM gets a
> > different signal where I could determine gas used? (the mass airflow
> > sensor, is there a relation there I'm missing?).
>
> You don't need the mass airflow sensor for this.  That just tells
> the computer
> how much air is coming in, so the ECU can determine how much fuel
> to send to
> the cylinders.  But other variables apply so it's not a fixed
> relationship.

        Hmm, ok.

> The fuel injectors have a litres-per-hour specification of how
> much fuel would
> flow if constantly open, in a given period of time at a given
> fuel pressure.
> You should be able to get that from the injector manufacturer.
> Check Bosch,
> Accel, Ford Motorsport, etc.

        Thanks, that would be the perfect spec, of course I'd have to find out
exactly what injector is being used, and hope to get the spec, thanks for
the pointer.

> Then the physics and math comes in.  The actual flow will be
> determined by the
> *difference* in pressure between the fuel at the injector tip
> (when open) and
> the pressure inside the intake manifold where the fuel is injected.  This
> means being able to measure the intake pressure, which your car should
> already be doing.  You just need to find/interpret the signal.

        Actually I think the intake manifold pressure is close to atmospheric (and
since the fuel rail is probably in the 40 to 60psi range assuming a value
might do), the car uses sequential port injection and doesn't have a turbo
or supercharger. Is the pressure difference REALLY that different? I've put
my hand in from of the MAF and didn't notice very much "suction", maybe
because the cross section is so big? I have never seen a manifold pressure
sensor on this engine. TTYL

--
http://www.piclist.com hint: To leave the PICList
mailto:piclist-unsubscribe-request@mitvma.mit.edu