[Diy_efi] pressure vs flow?

[Brian Michalk]

Thanks for the discussion.  I've got three references on the Bosch system
and know exactly what you are talking about.  I even blew over $1000 bucks
to get a brand-spanking new metering plate assembly, fuel distributor,
throttle body and Fuel Pressure regulator.

Man, the workmanship is incredible.  Unfortunately, the only component I
decided to use was the throttle body, and hopefully the injectors.  By the
way, if anyone wants a downdraft airflow sensor and fuel distributor for a
six cylinder engine, let me know.

As far as the FPR?  I put it in my lathe and turned it down so I could take
it apart to see how it worked.

I want to run my EFI system at 50psi, and use the CIS injectors as backup.
I like the atomization of the CIS injectors, but if they crack open at 30
PSI, I don't think I'll be able to get enough flow at 50PSI unless I crank
up my rail pressure to something closer to 90 or 100.  The only thing I
don't like about that is the electric fuel pump really eats a lot of current
making 100psi.

Again, this is for an airplane with two injection systems.  The EFI was
easy, the backup requires some more research.

So, back to the CIS issue.  The only thing that makes squirting possible is
pressure, therefore the plunger causes some sort of pressure variation.  I
thought someone on the list would know.  I'm getting to the point where I'll
need this information, so I'll put together some sort of test stand to
measure flow vs pressure.  I've got all the components, just thought someone
here could save me the trouble.

> I would guess that the pressure the injectors actually sees is slightly
> different from the "system" pressure because of the varying restriction
> presented by the height of the slit in the control plunger.
> However, Bosch
> does not calibrate off the injector pressure.  The "system" pressure is
> fixed, and the "control" pressure varies to alter the mixture for
> compensation (cold running, acceleration, boost mixture). Reducing
> the"control" pressure allows the air flow sensor plate to rise more for a
> given volume of air, exposing more of the slits and increase the
> volume of
> fuel delivered to the injector. Think of the airflow sensor as a
> "see-saw",
> as more air enters the system, one side rises, causing the other side to
> fall, exposing an increasingly larger opening to the injector
> fuel lines. The
> basic relationship is fixed, the "control" pressure loop just changes the
> weight balance of the "see-saw".  When control pressure is low
> (cold engine)
> there is a 40 lbs kid on the air flow side, as the engine warms
> up, the kid
> slowly puts on weight until he hits 100lbs (2.5times). KE and Lambda CIS
> alter a third pressure differential to slightly tweek the fuel delivery
> volume, but not by altering injector pressure directly.
>
> Bosch was actually quite surprised that it worked. The best part
> is 90 psi at
> the injector and that little pressure driven, wobbly pin
> atomizing the fuel.
>
> Paul Saltwick
>
>
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