Fuel Pressure and Rising-rate Pressure Regulators

Rising-rate Pressure Regulator

A rising-rate fuel pressure regulator

High pressure fuel pump

High-pressure roller-type fuel pump

On forced induction cars that use electronic fuel injection, you can use a rising-rate fuel pressure regulator to increase the fuel pressure proportional to the increase in boost pressure. The rising-rate fuel pressure regulator was developed by Ron Nash in the mid 1970's and has two adjustments: a needle-valve side adjustment that sets the maximum fuel pressure at maximum boost pressure, and a spring loaded onset screw that sets the boost pressure at which the fuel pressure will begin to increase. Note, however, that the rising-rate fuel pressure regulator does not replace the stock fuel pressure regulator but is used in conjuction with the stock fuel regulator. Using a rising-rate fuel pressure regulator allows you to retain the stock injectors but your fuel pump must be able to provide the required fuel pressure. In fact, it is preferable that the fuel pump supplys a little more than the maximum required fuel pressure. If your fuel pump does not provide sufficient fuel pressure, you will need to install a high-pressure fuel pump or a second fuel pump.

Using a rising-rate fuel pressure regulator allows you to maintain EFI timing and fuel delivery relative to signals from the air flow meter. Unfortunately, there are some limitations to using rising-rate fuel pressure regulator. Firstly, your stock fuel pressure regulator must be able to handle the increased pressure without its diaphragm failing. The stock fuel pressure regulator can usually handle up to 100 psi of fuel pressure so anything above 100 psi would become a problem. Fortunately, the fuel lines on an EFI equipped engine can safely withstand pressures well over 100 psi so there will be no need to replace them; but they should be checked for weaknesses. Secondly, and more importantly, the stock fuel injector will only operate correctly at up to 60 psi. Once the fuel pressure rises above 60 psi, the longevity of the injector will be greatly reduced. In addition, injector control will become quite erratic once the fuel pressure rises above 70 psi. Thus, this method of increasing fuel delivery is only practical for mild boost pressures of up to 9 psi. If you intend running higher boost pressures, you should consider installing a fully programmable aftermarket ECU that will allow you to program the ECU for the correct fuel delivery at different boost pressures and throttle positions.