idea..

[John Hess]

> ----------
> From: 	Paul Raley[SMTP:raleyp at UDel.Edu]
> Sent: 	Monday, October 06, 1997 10:07 PM
> To: 	diy_efi at coulomb.eng.ohio-state.edu
> Subject: 	Re: idea..
> 
> 
> 
> > someone mentioned trying to locate fuel flow meter to use for a
> mileage
> > calculator.  Why not have the ecu record the combined pulse width
> over a
> > period of distance, based on the assumption that fuel pressure
> remains
> > fairly constant, a certain distance traveled divided by the time the
> > injectors are open == MPG. All is needed is a pulse input from oneor
> more
> > of the wheels,  each pulse = a certain distance ,and the frequency
> is the
> > speed.
> 
> why could you assume the fuel pressure remains the same?  on my
> nissan, not
> only does the fuel pressure regulator (which not everyone has) alters
> the
> pressure, but the ECU controls the voltage of the pump, thereby
> varying
> pressure from 20psi to 60psi or more.   Don't other modern ECU's
> control the
> fuel pump voltage?
> 
> If you have a digital dash as on the nissan, the speed sensor could be
> used.
> This transmits two pulses for every revolution (optical).  The analog
> dash
> uses the same setup except that its magnetic and located in the dash
> itself.
> There are a number of Z's in the junkyard with these sensors located
> next to
> the battery under the speed control device.
> 
> Paul R.
> 
The GM unit varies the pressure according to vacuum (manifold pressure).