Stage X Parallel Fuel Rail Kit / Standard Fuel Regulator (Spec-C Models)

Parallel fuel lines give the injectors a more consistent volume of fuel and bring key safety benefits.

In the standard Subaru fuel system, the pump feeds fuel from the tank to the front of the car, through the fuel filter in the engine bay, and into the fuel rails. Fuel is then delivered to each cylinder one by one, starting with cylinder four. The fuel pressure regulator at the end of the rails acts like a flood gate, backing up the pressure so that each cylinder has a supply available.

A more efficient approach is to give each cylinder its own equal amount of fuel, so that no cylinder is left short compared with the rest. In the Stage X parallel fuel rail design, fuel leaves the fuel filter and passes through a Y-piece splitter that directs it to both rails at the same time. This avoids one cylinder running lean and lets the system hold more fuel in reserve, thanks to the larger-diameter rails and lines.

This kit is designed for unmodified vehicles where engine safety is the main goal. It is supplied with a conversion bracket to connect the standard fuel pressure regulator, so no mapping or manual tuning is needed after installation.

For vehicles modified for more power, the Stage X parallel fuel rail kit with the Stage X performance fuel regulator is recommended. It gives full control over fuel pressure where a greater volume of fuel is required.