Radium Engineering has released two fuel rail kits for Subaru Boxer engines found in the Impreza WRX/WRX STi, Legacy GT and Forester XT. This family of fuel rails and related accessories for the popular Subaru boxer engines covers model years from 2002 to 2015 (see applications below). These kits are designed for existing top-feed systems and for converting side-feed systems to top feed for optimum tuning and performance.
Subaru’s horizontally-opposed, 4-cylinder Boxer engine is extremely vulnerable to poor fuel delivery. The most common symptom is a lean spike stumble caused by pressure pulses in the fuel rail from injectors opening and closing, and large-bore fuel rails alone cannot alleviate this. Radium Engineering fuel rail kits offer an optional integrated fuel pulse damper that installs in any of the three 3/8″ NPT ports on the Radium fuel rails and eliminates this condition. The damper’s internal diaphragm absorbs oscillating pulses to help stabilize fuel pressure, improving both idle quality and power throughout the RPM range.
The restrictive OEM cross-over fuel piping also contributes to fuel pressure issues, particularly with the fuel demands of larger turbochargers. Radium’s Subaru Fuel Rail kits include four -6AN fittings to accommodate 3/8″ (9.5mm) hose, which can be configured in parallel (many Subaru tuners are convinced this design is essential for the Subaru fuel system) or in series.
Radium includes machined phenolic mounting spacers and washers in its Subaru Fuel Rail Kits to completely isolate the fuel rail from heat transferred from the TGV housings and mounting bolts.
Subaru Boxer Top-Feed Fuel Rail Conversion Fuel Rail Kit
Radium’s Subaru Top-Feed Conversion Fuel Rail Kit for Boxer engines converts the OEM side-feed fuel injector setup to top feed, allowing for the installation of a greater selection of more affordable fuel injectors (sold separately). It includes machined injector seats that insert into the fuel injector bores on the TGV housings to eliminate any chance of leaks, and different height injectors can be installed by swapping out the included insulating mounting boss spacers.
Depending on the vehicle’s country of origin, this fuel rail conversion kit is compatible with the following Subaru models:
2004-2006 Impreza WRX STi (with OEM side-feed injectors)
2005-2006 Legacy GT (with OEM side-feed injectors)
2004-2005 Forester XT (with OEM side-feed injectors)
Subaru Boxer Top-Feed Fuel Rail Upgrade Kit
Radium’s Subaru Top-Feed Fuel Rail Upgrade Rail Kit is a perfect bolt-in option for Boxer engines designed with factory top-feed injectors. Different height injectors (sold separately) can be used by swapping out the included insulating mounting boss spacers.
Depending on the vehicle’s country of origin, this fuel rail kit is compatible with the following Subaru models:
2002-2014 Impreza WRX (that came with top feed injectors)
2007-2015 Impreza WRX STi (that came with top feed injectors)
2007-2012 Legacy GT (that came with top feed injectors)
2006-2013 Forester XT (that came with top feed injectors)
JDM STi Spec-C Intake Manifold (when used with Radium 20-0172)
Subaru Fuel Rail Plumbing Options
Because there are multiple ways to configure fuel hose routing, Radium offers a selection of pre-made universal PTFE hoses (sold separately). To adapt -6AN hoses to the OEM feed and return hoses, Radium recommends using two Radium 14-0146 5/16″ SAE quick disconnect fittings.
Radium Subaru Boxer Fuel Rail Top-Feed Conversion & Upgrade Kit Features:
– Large 15.2mm (0.6″) internal diameter bore
– All 3 ports on each fuel rail are tapped with 3/8″ NPT
– Four 3/8″ NPT plugs included
– CNC machined from solid 6061 aluminum
– Black anodized and laser etched for a high quality surface finish
– Four -6AN male adapters included for “Parallel, Flow-Through” or “Series” fuel delivery
– Alcohol fuel compatible (E100, M100)
– Billet FPR adapter available if OEM fuel pressure regulator is used
– -8AN fittings available
– Optional fuel pulse dampers available and recommended
– Made in USA
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