Re: SPICA injection and wear

["Daegrigg (Don)" <daegrigg@domain.elided>]

Thanks for an excellent description.

Don

----- Original Message -----
From: "James Montebello" <jamesm@domain.elided>
To: "C M Smith" <cmsmith@domain.elided>
Cc: <alfa@domain.elided>
Sent: Monday, November 25, 2002 12:14 AM
Subject: Re: SPICA injection and wear


> On Sun, 24 Nov 2002, C M Smith wrote:
> > Of course the main problem with adapting a diesel injection system to
> > gasoline use is diesel fuel is a lubricant and gasoline is a solvent.
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) requires an oil supply and why most problems
>
> No. The pump is, in fact, a pump.  More accurately, it's four small
> piston pumps (eight for a Montreal).  The diesel pump the SPICA is
> derived from has to inject either directly into the cylinder or into a
> pre-chamber very late in the compression process, so it has to be under
> very high pressure to overcome the pressure in the combustion chamber.
> Each little piston pump delivers the fuel in the gasoline version at
> something near 100psi, which is why there are hard lines from the pump
> to the injectors (which are, in fact, just spring-loaded valves, set to
> only open above something like 70psi).  The fuel pressure supplied to
> the injection pump is only 7-9psi.  In this, it is very similar to the
> Bosch MFI, Kugelfischer, and Lucas mechanical injection systems.
>
> The Bosch K-Jetronic system has an actual fuel distributor/metering
> device.  In this system, the 100psi fuel pressure is supplied by a
> separate electric pump and a fixed mechanical regulator.  The distributor
> only regulates the amount of fuel based on the airflow demand of the
> engine, and all of the cylinders receive the same amount of fuel, which
> is constantly flowing to all of the cylinders (the K stands for the
> German word for constant) the entire time the engine is running, only
> the volume of the flow changes with demand.
>
> In the pump-type mechanical systems like SPICA, the fuel only flows some
> of the cylinders at any given time.  In the four-cylinder SPICA pump,
> only one cylinder is fed at any given time, timed to coincide with a valve
> event on that cylinder.  Such systems are referred to as sequential, and
> the EFI systems fitted on most cars today are sequential over at least
> part of the engine speed range, which improves emissions and economy.
>
> james montebello
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