Radium Engineering Subaru EJ Engines Fuel Rail Plumbing - Parallel - 2008-2021 Subaru STI

Radium Engineering Subaru EJ Engines Fuel Rail Plumbing - Parallel

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For Subaru EJ engines, the Radium Engineering fuel rail plumbing kit is designed to work seamlessly with existing fuel rail installations. It connects to the factory feed and return hard lines in the engine bay, located near the LH strut tower. Additionally, this kit includes all essential fittings and hoses for under hood fuel plumbing, and is compatible with all Radium Fuel Rails for Subaru EJ engines (excluding 20-0499 Fuel Rails). A RA-Series FPR is also included.

The RA-series regulators offer a groundbreaking tool-less pressure adjustment, eliminating the need for a jam nut and set screw. With just a turn of the knob, the pressure can be easily and precisely increased or decreased.

 

The incremental detents on the RA-series regulators allow for precise pressure adjustments, with each one providing 1psi (+/-0.5psi) depending on the current fuel pressure. These detents also offer haptic feedback to the user. Additionally, the regulators feature a 360 degree swivel vacuum reference port that is double O-ring sealed, making it the first of its kind in the industry. This convenient design allows for easy and tool-free directional adjustments by the installer.

 

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

1. 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).

2. 3AN Male Fitting:

A black zinc-plated adapter machined from high strength steel that is compatible with 3AN hose ends.

3. Push-To-Connect:

A nickel-plated brass fitting with Buna-N O-rings that is compatible with hard plastic 1/4" OD tubing.

4. Vacuum Plug:

A black oxide stainless steel screw that is used to maintain a constant (non dynamic) fuel pressure. 

 

Two kits are offered; one that feeds the fuel rails in series, and another that feed the fuel rails in a parallel configuration. Both kits perform equally well. The end decision is based on personal preference. Scroll down for details on each kit.

 

IMPORTANT NOTES

• Kit does not includes a fuel filter.
  
• Kit is not compatible with Radium dual port injector fuel rail kit 20-0499.
  
• Kit is safe to use with alcohol fuels such as methanol, ethanol, E85 etc.
  
• Kit uses 3/8" (6AN) high pressure EFI fuel hose.

 

Because the hoses and fittings are consolidated, the parallel kit is a good option for cleaning up the engine bay. Each fuel rail is fed as shown in the photo above. The feed and return lines enter the MPR-RA regulator from the rear and output through the front to the fuel rails.

 

The regulator secures to the LH strut tower using the provided stainless steel mounting bracket. 

 

A 0-100psi fuel pressure gauge is included for calibration. Fittings and 6AN hose are included to interface with the OEM feed and return hard lines. If aftermarket -AN hoses/lines have replaced the factory piping, this kit can still be used

 

Applications

• 2008-2014 Subaru Impreza STI
  
• 2015-2021 Subaru STI