Fuel pressure Regulators
Turbo Mini Forums

Alright chaps.


Im shortly going to be replacing the fuel pump on my supercharged mpi with a high capacity walbro one but im also starting to think that the fuel pressure regulator is faulty or sticking. I started the car a couple of days ago just to give it a run and the fuel pressure was at 2.5 bar (its set at 2 bar) i adjusted the regulator back down to 2bar and noticed that the engine note went noticably smoother, (didnt get the laptop out though to check the AFR's) Anyways aftyer about 5 mins of idling the fuel pressure had dropped to 1.5 bar so i had to up it back to 2 bar again.

My injectors are pre charger so they dont come under boost pressure and the car is mapped with a constant fuel pressure of 2 bar throughout the rev /load range.

The regulator installed is an FSE power boost valve which is a good few years old now as it was on the car before i even supercharged it, the vacuum port is to atmosphere.

If im to replace it do i have to go down the route of another power boost valve jobby or can i buy a cheaper simpler regulator which simply has to maintain 2 bar fuel pressure?

Thanks
Andy

It does sound likt there is a problem with the FPR
A quality fixed FPR is the Webcon (Weber Alpha) one and comes in varying pressures.

I have a 2.5bar one, brand new and I wont be needing it, if that is the pressure you are looking for.

However, it has been mentioned in the past that you should really have have the regulator referenced to the manifold pressure at the point that the injectors are located, this way making sure that the differential pressure across the pintle of the injector remains constant. If it is not referenced and just left open to atmosphere, the fuel pressure will be higher at idle than it would be at full throttle, the result being that the theoretical flow rate of the injector at idle is greater than nescisary, and could be less than desired at full throttle.

Most modern fuel injectors use 3bar fuel pressure referenced to the manifold at where the injectors are located. Gauge fuel pressure at idle would show ~2.3 bar.

Adjustable regulators are more trouble than they are worth, as human nature always wants you to adjust things because you can