Fuel system

A good quality fuel system of the appropriate specification is essential for the consistent fuelling of your engine up to your target power level. As a general rule you need the smallest injectors that you can still achieve your required power with, whilst still allowing a safety margin. In the case of fuel injectors you don't want to have to run over 90% duty cycle at peak power (although many people run up to 95% to achieve their target without resorting to larger injectors), whilst the supply to the fuel injectors needs to be maintained at a constant pressure above the inlet manifold pressure. The fuel pump needs to be able to flow a sufficient amount of fuel for your power requirements and also to supply it at the required pressure. While some pumps, like the popular Walbro units flow well at low to moderate fuel pressures, when building a fuel system for high power with the demands of increased base pressure and boost you need a setup that can supply high volume at high pressure. This can take the form of dual pumps, doubling up a pair of Walbro pumps, or moving to a higher flow single pump like the the Bosch motorsport 044 pump. For extreme installations, dual Bosch pumps may be required!

Products

Walbro in-tank high pressure fuel pump kit

Subaru

£80 +vat

In-tank electric fuel pump with a flow rate of 255L/hour (no load). This is an essential upgrade for cars modified for over 300hp, and in many cases where there the state of the original pump cannot be guaranteed. Suitable for power levels up to around 450hp.

Bosch 044 fuel pump

Subaru

£165 +vat

This fuel pump is significantly larger than the Walbro, so it is not a drop-in replacement for the OE pump. These pumps are usually fitted in-line, external to the tank. Although it has the same flow rating as the Walbro at zero pressure, the Bosch pump can can flow nearly all of its rated capacity at pressures up to 8 bar total. This pump is ideal as a single pump replacement for those wanting over 450hp.

650cc top feed injectors

Subaru Newage (set of 4) £300 +vat

Injector adaptor kit to fit phase 2 injectors to phase 1 rails

Subaru

£29.95 +vat

Allows injectors designed to fit phase 2 Subaru rails to be fitted into earlier 93-98 Impreza and Legacy.

Fuelab Fuel Pressure Regulator

Subaru

£175 +vat (inc. adaptor)

HyperFlow internal fuel anti-surge tank

Subaru MY01-05 WRX / STi

£190.16 +vat