Perhaps s little off topic, but when the Rutan airplane the 'voyager' flew aroun
d the world, they had an accurate fuel flow system measuring flow to the engine.
  As I recall, the completely forgot that the engine had a return line from the
carb/fuel injectors, so they thought they were out of fuel quite early.  Testing
 by measuring the speed at which the airplane stalled (related to the airplanes
weight) reassured them that the fuel was still (or again) in the tanks!

  Regards,
     Ron Fial

======================================
At 11:08 AM 6/27/98 +1000, you wrote:
>On Sat, Jun 27, 1998 at 09:05:50AM +1000, David Peterson wrote:
>
>> Another thought, is the return line really nesessary or can it be blocked,
>> early model vehicals didn't have them. Maybe the flow pressure wasn't as
>> high ? My old jalopy has an electric fuel pump with no reticulation.
>
>It is necessary; the fuel pumps used on injected engines are different
>to those used on carburetted engines. The pump for an injection system operates
>at a high pressure (it provides the injection pressure). The electric pumps
>used on carburettors basically provide a low pressure via a spring-loaded
>diaphragm with a solenoid to reload the spring as required; with no flow the
>pump simply stops. An injection type pump is quite different and the return
>line is required so that the pressure can be regulated (the injectors depend on
>a constant pressure).
>
>I suspect that cars with injection systems and trip computers get the fuel
>flow data from the engine controller, which calculates it from the injection
>parameters. To measure this externally would require monitoring of the pulse
>rate and duration to the injectors and knowing the parameters to convert this
>to flow rate.
>
>
>--
>Clyde Smith-Stubbs               |            HI-TECH Software
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