{"product_id":"bmw-s58-auxiliary-split-fuel-system","title":"BMW S58 Auxiliary Split Fuel System","description":"\u003cp\u003eThe \u003cstrong\u003eSpool Performance S58 Auxiliary Fuel System\u003c\/strong\u003e is designed for S58 owners pushing beyond the limits of the factory fuel system who want a solution that’s properly engineered, easy to install, and built for long-term reliability.\u003c\/p\u003e\n\u003cp\u003eFrom the start, our focus was on correct fuel architecture and real-world usability. Every component and layout choice was made to deliver stable, predictable fueling at higher power levels while keeping installation clean and OEM-friendly.\u003c\/p\u003e\n\u003ch3\u003eWhy a Properly Split DI + PI Fuel System Matters\u003c\/h3\u003e\n\u003cp\u003eAs power levels increase on the S58 platform, fueling challenges typically come from \u003cstrong\u003esupplying direct injection (DI) and port injection (PI) from the same fuel feed\u003c\/strong\u003e.\u003c\/p\u003e\n\u003cp\u003eWhen DI and PI share a feed:\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cp\u003eThe pulsed nature of DI can introduce pressure fluctuations that disrupt fuel flow to the PI injectors\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003ePort injection requires boost-referenced fuel pressure to maintain consistent injector differential under load\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eAt higher boost and airflow, maintaining precise and repeatable fueling becomes more difficult\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eBy separating the DI and PI supply, each system operates independently and exactly as intended. The result is \u003cstrong\u003esmoother fuel delivery, improved consistency, and greater confidence as power increases\u003c\/strong\u003e.\u003c\/p\u003e\n\u003ch3\u003eDesigned to Install Cleanly\u003c\/h3\u003e\n\u003cp\u003eA significant amount of development time went into making this system straightforward to install without unnecessary modifications.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eThe OEM fuel pump top hat is retained using additional precision-machined aluminum fuel fittings that integrate directly into the factory top hat\u003c\/strong\u003e, eliminating the need for repinning or modifying factory wiring\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eA plug-and-play wiring harness is supplied for direct compatibility with the Reflex controller\u003c\/strong\u003e, simplifying installation and control\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eThese design choices keep the install clean, reduce complexity, and maintain a factory-like fit and finish.\u003c\/p\u003e\n\u003ch3\u003eScalable Pump and Control Options\u003c\/h3\u003e\n\u003cp\u003eThe system is built to grow with your setup:\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eDual Walbro 450 fuel pumps included standard\u003c\/strong\u003e\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eOptional Walbro 525 upgrades\u003c\/strong\u003e available for higher horsepower goals\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eChoice of:\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cp\u003eStandard relay configuration\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eSolid-state relay option\u003c\/strong\u003e for full PWM pump control \u003cmeta charset=\"utf-8\"\u003eavailable for purchase separately. NOTE: 2 harnesses required per AFS Kit - Link to Harness: https:\/\/spoolperformance.com\/products\/spool-lpfp-pwm-activation-harness-bmw?_pos=1\u0026amp;_sid=2a7c2a7b8\u0026amp;_ss=r\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eThis flexibility allows you to match the fuel system to your current build while leaving room to expand.\u003c\/p\u003e\n\u003ch3\u003eHigh-Quality Fuel Plumbing\u003c\/h3\u003e\n\u003cp\u003eAll fuel lines included in the kit feature \u003cstrong\u003etriple-layer PTFE construction\u003c\/strong\u003e:\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cp\u003eInner \u003cstrong\u003ePTFE core\u003c\/strong\u003e for full fuel and ethanol compatibility\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eMiddle \u003cstrong\u003estainless steel reinforcement\u003c\/strong\u003e for pressure strength\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eOuter \u003cstrong\u003enylon protective layer\u003c\/strong\u003e for abrasion resistance and durability\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003cp\u003eThis ensures long-term reliability in high-heat, high-vibration environments.\u003c\/p\u003e\n\u003ch3\u003eCompact, Purpose-Built Fuel Pressure Regulation\u003c\/h3\u003e\n\u003cp\u003eThe system includes Radium Engineering's FPR.\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cp\u003eBoost-referenced for accurate pressure control under load\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eStable regulation at high flow rates\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eCompact design for clean engine bay packaging\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003eBuilt to withstand demanding conditions\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eBuilt to Support Serious S58 Builds\u003c\/h3\u003e\n\u003cp\u003eWhether you’re building a strong street car or planning a higher-power setup, the Spool Performance S58 Auxiliary Fuel System delivers the fueling control and capacity needed to push the S58 platform with confidence.\u003c\/p\u003e\n\u003cp\u003eWith properly separated DI and PI supply, OEM-friendly integration using precision aluminum fittings, Reflex compatibility, high-quality plumbing, and scalable pump options, this system is designed to perform reliably as your build evolves.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eIf you’re ready to upgrade your S58 fueling with a system that’s thoughtfully engineered and genuinely easy to live with, this is the solution built to get you there.\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003e \u003c\/p\u003e\n\u003ch3\u003e\u003cstrong\u003eFitment\u003c\/strong\u003e\u003c\/h3\u003e\n\u003cp\u003eThis auxiliary fuel system is designed for BMW vehicles equipped with the \u003cstrong\u003eS58 engine\u003c\/strong\u003e, including:\u003c\/p\u003e\n\u003cul\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eBMW M3 (G80)\u003c\/strong\u003e – 2021+\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eBMW M3 Touring (G81)\u003c\/strong\u003e – 2023+\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eBMW M4 (G82 \/ G83)\u003c\/strong\u003e – 2021+\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eBMW M2 (G87)\u003c\/strong\u003e – 2023+\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eBMW X3 M (F97)\u003c\/strong\u003e – 2020–2024\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eBMW X4 M (F98)\u003c\/strong\u003e – 2020–2024\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Spool Performance","offers":[{"title":"Walbro 450 with check valves","offer_id":50416493461761,"sku":"SP-S58AUXF450","price":1299.0,"currency_code":"USD","in_stock":true},{"title":"Walbro 525 with check valves","offer_id":50416493494529,"sku":"SP-S58AUXF525","price":1599.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0842\/4610\/2273\/files\/1_ebebb647-772f-41ae-a53d-304a5c741f8c.png?v=1790644716","url":"https:\/\/fphpro.com\/products\/bmw-s58-auxiliary-split-fuel-system","provider":"Flako performance house","version":"1.0","type":"link"}