RADIUMAUTO Fuel Pressure Regulator Kit for Subaru WRX STi EJ257
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This kit is for use in the USDM 2008-2021 Subaru WRX STi (EJ257 only). It replaces the OEM fuel pressure regulator and damper assembly shown below. The factory STi fuel line routing uses a quasi-dead-end system that circulates fuel through the regulator, bypassing the engine in the process. Fuel is directed to the engine only when there is a need.
The Radium FPR kit replaces the factory regulator and redirects fuel so it travels through the engine lines before it reaches the regulator and returns to the tank. This is the preferred fuel line routing used by Subaru tuners trying to troubleshoot stumbling issues. The radium fuel pressure regulator offers an adjustment from 20 psi upwards with a 1:1 vacuum reference. Interchangeable orifices allow the user to tune the regulator to any fuel pump flow.
The kit installs in the same location as the OEM fuel pressure regulator. Also included is a vacuum hose and fittings to route the vacuum reference line from cylinder #4 to the intake manifold for a more stable vacuum signal. The optional gauge kit 20-0386 can be installed into the unused 8AN ORB port on the regulator as shown above.
There are also 2 options for the color of the top of the fuel pressure regulator. The green variant (20-0265-01) is shown above.
NOTE : Despite being a high flow pressure regulator, the fuel system still suffers with the restrictive OEM venturi jet pump. It is recommended to upgrade the OEM fuel pump assembly. Alternatively, a fuel impulse dampener can be installed in the return line to reduce the vibration caused by this unwanted restriction.