base fuel pressure for FPR?
 

I have an Aeromotive rising rate fuel pressure regulator. I know that it increases fuel pressure 1 psi per 1 psi of boost but what do i need to set the base pressure to?

39psi static

Re: base fuel pressure for FPR?
 

Just for the record, what you're describing is a set rate regulator, not rising rate.

Ok, so then whats the difference. I always thought a non rising rate had no vaccum/boost connection, wile a rising rate used a boost singal as reference to increase the fuel pressure.

A set rate regulator raises the pressure at a set rate, 1:1. It will keep your fuel pressure at a constant level relative to your manifold pressure (or whatever reference pressure you feed it through the little vaccum line).

A rising rate regulator will raise your fuel pressure at a rising rate, like 1:2, 1:3, 1:4. A 1:3 RRFPR will cause your fuel pressure to rise 3 times as much as the increase in reference pressure (3 psi of fuel pressure for every psi of boost).

RRFPRs are a simple, inexact way of pushing your fuel delivery system, often used when proper tuning is not an option b/c of cost or other reasons. Imagine tweaking a fuel map when 30% more injector duty cycle doesn't equal 30% more fuel, pretty confusing.

(edit: man, I spell like a swede..)

ah.... so i see

Rising rate increases the amount of fuel flowed per duty cycle of the injectors by upping the fuel pressure.

The amount of fuel that comes out of the injectors per unit of time is determined by the pressure difference between the front and back(fuel rail) side of the injectors. Fuel rail pressure by itself doesn't mean much without taking into consideration the manifold pressure. Say you start with 40psi with zero vac or pressure. With a std FPR when your mani pressure increases to 1psi the FPR will up the fuel rail pressure to 41psi. This will preserve the gradient (41-1=40). With a RRfpr set at 1:2 when the mani pressure increases to 1psi fuel pressure will be bumped to 42psi, increasing the gradient by 1 (42-1=41psi).

The only non-economic advantage I see to using a RRFPR is that it allows you to run more streetable injectors while providing capacity that is similar to that of larger injectors.

edit

38 to 40psi static (static meaning with the engine off and the fuel pump running).

B

I had that confused too...
Good info...