A fuel pressure regulator (FPR) is a device which controls the pressure of fuel supplied to the fuel injectors on an engine.
A Turbosmart Fuel Pressure Regulator (Turbosmart FPR800, Turbosmart FPR1200, Turbosmart FPR2000) works by bleeding off a portion of the fuel flow to the injectors from the fuel pump to control the fuel pressure.
Fuel is pumped from the fuel tank to the fuel rail by the fuel pump. The FPR is normally mounted after the fuel rail to ensure that the fuel rail has priority in fuel flow. The valve in the FPR controls the amount of fuel that is bled from the fuel rail by opening an outlet port to allow fuel to flow back into the fuel tank.
All injectors need a pressure difference between the inlet and the outlet of the injector to spray fuel into the combustion chamber. This is called the base pressure. The base pressure is adjusted on all Turbosmart FPR’s via the adjustment screw to suit the injectors and fuel pump system you are using.
The adjustment screw pushes down on a spring which applies a force onto the valve. When the pressure inside the bottom chamber of the FPR exerts a high enough force on the valve to overcome the spring force and lift the valve off its seat, it allows fuel to flow through the outlet port effectively controlling the fuel pressure in the fuel rail.