Precision Raceworks M3/M4/M340i/M440i (G8x/G2x) Stand Alone AFS™ – BMW B58/S58

Overview

Once you add port injection to a direct-injected M340i/M440i (B58) or M3/M4 (S58), the factory low-pressure fuel system becomes the weak link. The factory pump is PWM-controlled to reduce output once target fuel pressure is reached, putting it in constant conflict with any pump trying to feed port injection, and the HPFP's control system dumps fuel back at high pressure/low volume, causing pressure oscillations. The Precision Raceworks Stand Alone AFS™ solves this by adding a completely dedicated, independent fuel system just for port injection — now with plug-and-play connectors and AN8 adapters, so the factory harness no longer needs to be cut.

Details

• Part Numbers: 601-0281 (AFS.425) / 601-0282 (AFS.460) / 601-0283 (AFS.640) / 601-0284 (AFS.745) / 601-0285 (AFS.800)
• Fully separate low-pressure fuel system for port injection, independent of the factory pump and PWM control
• Billet aluminum top hat with 3 high-flow fuel ports
• Fully adjustable, 1:1 boost-scalable billet fuel pressure regulator
• 10-micron USA-made Microglass fuel filter, ideal for E85
• Smooth-bore, high-flow PTFE feed and return lines (AN6)
• Pump options: AFS.425 (single Walbro 450, 425 LPH @ 3 bar), AFS.460 (single Walbro 535, 460 LPH @ 3 bar), AFS.640 (dual Walbro 450s, 640 LPH combined @ 3 bar), AFS.745 (Walbro 450 + Walbro 535, 745 LPH combined @ 3 bar), AFS.800 (dual Walbro 535s, 800 LPH combined @ 3 bar)
• 100% E85 compatible across all components
• Includes: Walbro fuel pump(s) per configuration, billet top hat and fuel pressure regulator, 10-micron Microglass fuel filter, PTFE feed/return lines and fittings, and a configurable pump activation harness

Installation Notes

Designed for port injection kits where the fuel rail mounts above the manifold — if running a plate-style spacer PI setup, confirm compatibility before ordering. Some fuel rails may require a Male AN8-ORB to Female AN6-ORB adapter (not included). If your tuner wants Solid State Relays, one is needed per pump — see the Solid State Relay Upgrade Kit. For the M3/M4 (G80/G82, S58), this AFS feeds the port injection setup from the Precision Raceworks S58 Port Injection Kit.

• PDF install instructions
• Video installation instructions
• Pump activation harness instructions (PDF)
• Setting fuel pressure — adjustable regulator (PDF)

Vehicle Application