A fuel pressure regulator (FPR) is a component that manages the pressure of fuel delivered to the fuel injectors in an engine.
A Turbosmart FPR regulates fuel pressure by diverting a portion of the fuel flow from the fuel pump to the injectors. The fuel pump sends fuel from the fuel tank to the fuel rail, and the FPR is typically positioned after the fuel rail. This placement ensures that the fuel rail receives fuel first. The FPR's valve adjusts the amount of fuel redirected from the fuel rail by opening an outlet port, allowing excess fuel to return to the fuel tank.
Base Pressure
All injectors require a pressure difference between the inlet and the outlet of the injector to properly spray fuel into the combustion chamber. This is known as the base pressure. The base pressure can be adjusted on all Turbosmart FPRs using the adjustment screw to match the injectors and fuel pump system in use.
The adjustment screw compresses a spring, which applies force to the valve. When the pressure in the bottom chamber of the FPR becomes strong enough to overcome the spring force, it lifts the valve off its seat. This action allows fuel to flow through the outlet port, thereby regulating the fuel pressure in the fuel rail.
Since the outlet of the injector is exposed to manifold vacuum/pressure, which varies with throttle movement, while the fuel flow from the fuel pump remains constant, the valve requires a reference to adjust the amount of fuel bled off and maintain constant fuel pressure to the injectors. Besides the spring force acting on the valve, a vacuum/boost signal also exerts a force on the valve. This ensures the valve consistently maintains a constant pressure difference between the inlet and outlet of the injector.
The base pressure is set with no line connected to the vacuum/boost reference nipple. After the base pressure is established, the vacuum/boost line is then connected to the reference nipple.
For example, with a base pressure of 40 PSI, if the engine is idling at 20 inHg, the nozzle experiences 20 inHg of vacuum, causing fuel to be drawn into the intake manifold. This vacuum, combined with the 40 PSI base pressure, would theoretically result in a spray pressure of 50 PSI, which is higher than the desired 40 PSI. However, since the top of the valve in the FPR is also exposed to 20 inHg, the valve is pulled upward, opening the outlet port and increasing the amount of fuel bled from the fuel rail. This reduces the pressure by 10 PSI, achieving the desired fuel pressure of 40 PSI.
At a boost pressure of 10 PSI, the nozzle is subjected to 10 PSI of pressure, which opposes the base fuel pressure, resulting in a spray pressure of 30 PSI—below the target fuel pressure. By also supplying the top of the valve with a reference boost signal of 10 PSI, the FPR combines forces to provide 50 PSI of fuel pressure. This overcomes the opposing force at the nozzle, ensuring the target pressure of 40 PSI is maintained.
At a boost pressure of 10 PSI, the nozzle is subjected to 10 PSI of pressure, which opposes the base fuel pressure, resulting in a spray pressure of 30 PSI—below the target fuel pressure. By also supplying the top of the valve with a reference boost signal of 10 PSI, the FPR combines forces to provide 50 PSI of fuel pressure. This overcomes the opposing force at the nozzle, ensuring the target pressure of 40 PSI is maintained.
This refers to the relationship between boost pressure and fuel pressure increase. A 1:1 ratio means that for every 1 PSI increase in boost pressure, the fuel pressure will also increase by 1 PSI. This ensures that the pressure differential between the inlet and outlet of the injector remains constant. Injectors are rated for a specific base pressure and are essentially solenoid valves that open and close when power is applied.
The injector has a solenoid that provides enough force to open the valve, overcoming the fuel pressure that keeps it closed. If the fuel pressure is too high, the solenoid may not have enough energy to fully open the valve, leading to a lack of fuel supply to the engine. Therefore, it is crucial to maintain a constant pressure differential between the inlet and outlet of the injector, making a 1:1 ratio FPR ideal. All Turbosmart FPRs feature a 1:1 rising rate.
Electric Fuel Pumps
Electric fuel pumps are designed to deliver a consistent amount of fuel regardless of engine RPM and/or boost pressure. At idle, the fuel regulator needs to handle the maximum flow of fuel, as the fuel pump operates at maximum capacity while the engine consumes minimal fuel. If the FPR cannot flow enough fuel, the fuel pressure will exceed the desired level.
In high horsepower cars using mechanical fuel pumps, a high-flow FPR is crucial. Mechanical fuel pumps are engine-driven, meaning fuel flow increases with engine RPM. At the end of a drag race, for example, engine RPM is high while the throttle is closed, causing the engine to use minimal fuel. The FPR must be able to divert large amounts of fuel in these situations to maintain the optimal fuel pressure differential between the inlet and outlet of the injector. Insufficient flow from an FPR can cause large pressure spikes, potentially damaging injectors or causing mechanical failure in fuel rails and lines. All Turbosmart FPRs are designed for high flow and can support a fuel system compatible with the model of FPR.
Modern fuels often contain various chemicals to increase their octane rating, which helps reduce engine knock. However, fuels like alcohol and unleaded race fuels can corrode untreated metals and damage diaphragms. All Turbosmart FPRs feature anodized billet aluminum bodies for strength and corrosion resistance. The FPR800 is equipped with a diaphragm that can withstand any type of pump fuel, while the FPR1200, FPR2000, and FPR3000 models have diaphragms capable of handling any type of race fuel or alcohol.
Base Pressure
Every injector comes with a manufacturer-recommended optimal working base pressure. It's crucial to adjust the FPR to deliver this optimal base pressure. Turbosmart FPRs feature adjustment screws that let the user set the base pressure between 30 and 70 PSI. This adjustability allows them to be compatible with any type of fuel injector and fuel pump.
The target power level dictates the amount of fuel required from the fuel pumps and the capacity the FPR must manage. Higher target power levels demand more fuel flow, necessitating a larger FPR to maintain the desired pressure levels. In summary, all Turbosmart FPRs are rated according to the horsepower they can control. For instance, the FPR1200 can manage fuel flow for up to 1200 horsepower.
It's important to select an FPR that can handle the type of fuel used in the engine. For streetcars using pump fuel, the FPR800 is suitable. However, race cars running on race fuel or alcohol will need higher series FPRs, such as the FPR1200, FPR2000, or FPR3000.
