Posted for "Ed Anderson" <eanderson@carolina.rr.com>:

Welcome to the club,David {:>) lots of things I don't understand also- but,
here is my
crack at your question.  My pumps puts out approx 80 psi at idle (without
pressure regulator) when new and the flow rate was given in the specs as 43
gph at 45 psi.  Clearnly adequate even for a turbo 13B.

The main pump, after 5 years of use, is down to about 65 psi (without
pressure regulator) - so apparently it is getting a bit worn from use and
due to be replaced.  This pressure is without the
pressure regulator.  With the pressure regulator, I have it set so I get
approx 43 psi.  Of course, the way I get 43 psi is to set the regulator to
by-pass sufficient
fuel back to my header tank to drop the line pressure from 65-80 psi to 43
psi.  It does not take much fuel being by-passed by the regulator back to my
sump to drop the pressure quite a bit.  Imagine trying to maintain 80 psi
from the pump with a 1/4-3/8" dia hole in the line.  I estimated at one
point that my regulator by-passed a max of approx 8-9 gallon hour and that
was at idle.  Less fuel is returned when the injectors are full blast.  I
have seen over 20 gph fuel flow on a cold morning.

I am not certain that the pump is working harder with more flow.  It may be
that the pressure regulator is simply not diverting as much of the pump's
flow back to the tank.  .  If pressure were required to be maintained at say
60 psi at 16 gph for example then it would have to work harder than if it
maintained 16 gph at 43 psi.  But, more importantly that is why the pump
rating should accommodate the intended application.  These pumps would
clearly not support a 1000 HP dragester fuel flow needs for example.

Perhaps this helps a bit.

Ed