Re: SPICA injection and wear

[bearbvd@domain.elided (Greg Hermann)]

At 7:43 PM 11/24/02, Tony Sims wrote:
>> That
>> is why the SPICA distributor (some refer to it as a pump as it seems to
>> fill that function, but in truth the "pump" portion is merely a
>distributor
>> or metering device)
>
>Are you sure this is true, Michael?  The fuel pressure at the injectors in a
>Spica system is quite high, well above what the fuel pump from the tank
>provides.  As I understand it, the little pistons in the Spica draw in a
>metered amount of fuel based on the position of the 3-d cam, and then force
>it into the individual lines leading to the injectors, creating the
>necessary pressure to force the injector to open.  It appears to me that it
>is truly a pump, using the same basic action as a piston air compressor.
>
>I'm certainly no expert, and this could merely be a case of semantics or my
>ignorance of the actual function of the Spica "pump".

You are correct, Tony.

The pump (actually four of them) is positive, but variable displacement.
The "rack" controls the displacement, and the position of the rack is
determined by the three dimensional cam and linkage. The metering scheme is
generally known as "alpha-N" in the injection trade--for throttle position
and RPM.

Michael is also mistaken to claim that "any" injection is superior to
Webers, but we've already been there.

Greg
>
>Cheers,
>Tony
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