BMW B58 Gen 1 Spool Auxiliary Split Fuel System

The Spool auxiliary split fuel system for the Gen 1 B58 gives direct injection and port injection their own fuel supply for stable fueling at high power.

Why you need it

When DI and PI share one feed, the pulsing of the direct injection system can upset flow to the port injectors, and the port side needs boost-referenced pressure to hold a consistent injector differential. Separating the two lets each system work as intended, for smoother, more repeatable fueling as boost goes up. The factory top hat is retained with machined aluminum fittings, so there is no repinning or factory wiring to modify.

Fits

• BMW M240i & M240i xDrive (F22/F23), 2016 to 2018
• BMW 340i & 340i xDrive (F30/F31/F34), 2016 to 2018
• BMW 440i & 440i xDrive (F32/F33/F36), 2016 to 2018
• Other BMW with the Gen 1 B58B30 engine

What's included

• Dual Walbro 450 or Walbro 525 fuel pumps with check valves (selected at checkout)
• Precision-machined aluminum fittings for the factory top hat
• Plug-and-play wiring harness for the Reflex controller
• Triple-layer fuel lines: PTFE core, stainless reinforcement, nylon outer layer
• Radium Engineering boost-referenced fuel pressure regulator

Good to know

Made for the Gen 1 B58 (B58B30) only and not for Gen 2 / B58TU engines. The Walbro 450 pumps suit most builds; the 525 option is for higher power goals. For full PWM pump control, two Spool PWM activation harnesses are needed and are sold separately. A supporting tune is required. Professional installation is recommended.