Once you add port injection to a direct-injected M240i (B58) or M2 (S58), the factory low-pressure fuel system becomes the weak link. The factory pump is controlled by PWM designed to reduce output once target fuel pressure (typically 5 bar) is reached — which puts it in constant conflict with any upgraded or added pump trying to feed port injection. On top of that, the high-pressure pump's control system dumps fuel back into the low-pressure system at high pressure/low volume, causing pressure oscillations that limit how consistently an upgraded pump can perform.
The Precision Raceworks Stand Alone AFS™ (Auxiliary Fuel System) solves this at the source: instead of trying to make the factory low-pressure system do double duty, it adds a completely dedicated, independent fuel system just for your port injection setup. Now featuring plug and play connectors and AN8 adapters, so it's no longer necessary to cut the factory harness.
SPECS
Dedicated system: A fully separate low-pressure fuel system for port injection — completely independent of the factory pump and its PWM control
Billet top hat: Billet aluminum top hat with 3 high-flow fuel ports
Filtration: 10-micron USA-made Microglass fuel filter, ideal for E85
Lines: Smooth-bore, high-flow PTFE feed and return lines (AN6)
Pump Selection: unlike the other AFS vehicle groups, this SKU is offered in only 3 tiers per Precision Raceworks' own listing — AFS.460 (single Walbro 535, 460 LPH @ 3 bar), AFS.640 (dual Walbro 450s, 640 LPH combined @ 3 bar), AFS.800 (dual Walbro 535s, 800 LPH combined @ 3 bar)
100% ethanol compatible: All components rated for full E85 compatibility
PARTS INCLUDED
Walbro fuel pump(s) per selected configuration
Billet aluminum top hat and fuel pressure regulator
10-micron Microglass fuel filter
PTFE feed/return lines and fittings
Configurable pump activation harness
TECH RESOURCES
Designed for use with a port injection kit where the fuel rail is mounted above the manifold. If you're running a plate-style spacer PI setup, contact Precision Raceworks directly before ordering to confirm compatibility.
Some fuel rails may require a Male AN8-ORB to Female AN6-ORB adapter for compatibility (not included).
