Radium Engineering Fuel Pressure Regulator Kit Black 2008-2021 STI

Upgrade your fuel system with the Radium Fuel Pressure Regulator (FPR) Kit, designed specifically for USDM 2008-2021 Subaru WRX STi models with the EJ257 engine. This kit replaces the OEM fuel pressure regulator and damper assembly, optimizing fuel rail flow and improving stability under high-performance conditions.

The Radium FPR kit reroutes fuel through the fuel rails before returning to the tank, promoting smoother fuel delivery and eliminating potential stumbling caused by the OEM quasi dead-end system. Engineered for tuners and performance enthusiasts, this kit provides precision control, improved reliability, and easy installation, making it a must-have upgrade for EJ257-equipped WRX STi owners.

Features:

• Replaces the OEM regulator in the stock location with improved fuel rail circulation
• Preferred fuel line routing for tuners to address stumbling or fuel delivery inconsistencies
• Includes vacuum hose and fittings to re-route the vacuum reference line from the #4 cylinder runner to the intake manifold plenum for a stable signal
• The optional pressure gauge kit (20-0386) can be installed into the unused 8AN ORB port on the regulator
• First tool-less fuel pressure adjustment in the industry—no jam nut or set screw required
• Incremental detents provide tactile feedback, allowing 1 psi (+/-0.5 psi) adjustment per detent
• Newly designed single stainless steel return orifice enhances laminar flow and stability control
• 360° swiveling vacuum reference port with double O-ring sealing allows for easy orientation without tools

There are 4 interchangeable 10-32 threaded vacuum port fittings provided to cover all scenarios:

• Barbed Fitting: A black zinc-plated 3/16" (5mm) barb machined from high strength steel that is compatible with the following vacuum hoses: 5/32" (4mm), 3/16" (5mm), and 7/32" (6mm).
•  3AN Male Fitting: A black zinc-plated adapter machined from high strength steel that is compatible with 3AN hose ends.
  
• Push-To-Connect: A nickel-plated brass fitting with Buna-N O-rings that is compatible with hard plastic 1/4" OD tubing.
  
• Vacuum Plug: A black oxide stainless steel screw that is used to maintain a constant (non dynamic) fuel pressure. 
  

This FPR kit is suitable with all gasoline types including unleaded, leaded, oxygenated, and pre-mixes. Furthermore, it is compatible with alcohol blends of fuel including methanol, ethanol, and E85. 

Installation Instructions