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