{"product_id":"radium-fuel-pressure-regulator-kit-2008-2017-subaru-sti-20-0265","title":"Radium Fuel Pressure Regulator Kit | 2008-2021 Subaru STI (20-0965)","description":"\u003cp\u003e\u003cstrong\u003eThe GR\/GV STI's quasi dead-end fuel routing is behind more stumble complaints than most owners realize.\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eFrom the factory, the 2008-2021 STI circulates fuel through the regulator and only sends it to the engine on demand, a layout Subaru tuners have long worked around. The \u003cstrong\u003eRadium Engineering Fuel Pressure Regulator Kit\u003c\/strong\u003e replaces the OEM regulator and damper assembly and re-routes fuel to cycle through the fuel rails before reaching the regulator and returning to the tank, the routing tuners prefer for chasing out stumble issues. The RA-series regulator at its core brings tool-less pressure adjustment with 1 psi detents and a 360-degree swiveling vacuum port. It installs in the factory regulator location, no relocation bracketry needed.\u003c\/p\u003e\n\u003ch3\u003eWhat You'll Feel\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eSmoother, more consistent running as constant flow through the rails replaces the dead-end routing\u003c\/li\u003e\n\u003cli\u003eBase pressure changes by hand in seconds, with haptic detents instead of a jam nut and set screw\u003c\/li\u003e\n\u003cli\u003eA more stable vacuum signal to the regulator, re-referenced from the plenum instead of the #4 runner\u003c\/li\u003e\n\u003cli\u003eA cleaner engine bay with the regulator sitting exactly where the factory unit lived\u003c\/li\u003e\n\u003cli\u003eEasy pressure checks if you add the optional gauge to the spare port\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eFeatures\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eReplaces the OEM fuel pressure regulator and damper assembly on the USDM EJ257 STI\u003c\/li\u003e\n\u003cli\u003eRe-routes fuel through the rails before the regulator, the preferred routing for addressing stumbling\u003c\/li\u003e\n\u003cli\u003eRA-series regulator with tool-less knob adjustment; each detent changes pressure roughly 1 psi (+\/- 0.5 psi)\u003c\/li\u003e\n\u003cli\u003eSingle stainless steel return orifice generates laminar flow for enhanced pressure stability\u003c\/li\u003e\n\u003cli\u003e360-degree swiveling, double O-ring sealed vacuum reference port\u003c\/li\u003e\n\u003cli\u003eUnused 8AN ORB port accepts the optional Radium 20-0386 pressure gauge kit, sold separately\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eThe Details\u003c\/h3\u003e\n\u003cp\u003eThe factory system's weakness is that fuel loiters at the regulator instead of continuously sweeping through the rails, which invites pressure inconsistency at the injectors. This kit reverses that: feed enters the rails, flows through them, then meets the regulator before returning to the tank, so the injectors always sit in moving, pressure-controlled fuel. The included vacuum hose and fittings relocate the regulator's reference signal from the #4 cylinder runner to the intake manifold plenum, trading a pulsing single-runner signal for a stable average that the diaphragm can actually track. Adjustment is where the RA-series stands apart: turn the knob and feel each detent click off roughly 1 psi, no wrenches, no jam nut, no set screw. Installation happens in the stock regulator location with the OEM lines, and if you want eyes on your base pressure, the spare 8AN ORB port takes Radium's 90-degree gauge kit. This kit is specific to the USDM EJ257 STI, so 2015-2021 WRX FA20DIT owners need to look elsewhere.\u003c\/p\u003e\n\u003ch3\u003eKit Includes\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e1x RA-series direct mount fuel pressure regulator (black)\u003c\/li\u003e\n\u003cli\u003eMounting and adapter hardware for the OEM regulator location\u003c\/li\u003e\n\u003cli\u003eVacuum hose and fittings to re-route the reference line to the intake manifold plenum\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eApplications\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003e2008-2021 Subaru WRX STI (USDM, EJ257 engine only)\u003c\/li\u003e\n\u003cli\u003eNot compatible with 2015-2021 Subaru WRX (FA20DIT)\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Radium Engineering","offers":[{"title":"Default Title","offer_id":43672688427075,"sku":"20-0965","price":256.45,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0064\/7754\/5539\/files\/radium-engineering-rad-20-0965-00-30957279871046_18b93f96-e395-43ab-9622-00a564510747.jpg?v=1786717051","url":"https:\/\/www.tunedbyshawn.com\/products\/radium-fuel-pressure-regulator-kit-2008-2017-subaru-sti-20-0265","provider":"Tuned by Shawn","version":"1.0","type":"link"}