I agree with your statement,
Buly. Ideally if the pressure differential between fuel rail and
manifold is kept constant by use of a manifold reference then that
would imply that the fuel pressure should vary to compensate for different
manifold pressure. However, my fuel pressure is rock steady and this
is the second manifold-referenced fuel pressure regulator I have used with
no difference.
Ed;
I’d
say it is clear that your FPR is not functioning properly; although the
problem may not be in the pressure regulator. You may want to check to
make sure the manifold pressure (vacuum) is really being seen at the
regulator.
The
fact that the fuel pressure does not change with MP is not a big issue for
NA engine. The idea of MP referencing of the fuel pressure came with
super/turbo charging; the purpose is to keep the pressure differential
across the injector nozzle from getting too low as the boost went up.
It is an issue with the EC2 because the default mixture mapping is set up
for MAP referenced fuel pressure.
I
did all the dyno runs with my engine without MAP reference; fixed at 40
psi. This was before I knew that the EC2 was set up for MAP referenced
FP for NA application. It worked fine except it was difficult to get
things lean enough at idle.
With
my current MAP referenced FPR and one fuel pump running, I have about 41 psi
fuel pressure with a MAP of 30”, and about 31-32 psi at a MAP of
11-12”. So that’s about a 9 psi change in MAP resulting in about 9 psi
change in fuel pressure. Keeps the pressure differential that the
injector sees constant. With both FPs running, the fuel pressure is a
couple psi higher.
It
was interesting yesterday; I ran the engine until the fuel tank was
empty. I watched the FP as the pump started to suck air. I
turned the mixture knob up as the FP started to drop. The engine continued
to run at low power until pressure got down to about 9
psi.
Al