Precision Raceworks Stand Alone Auxiliary Fuel System - BMW G8X/G2X

Precision Raceworks' Stand Alone Auxiliary Fuel System (AFS) gives your G8X/G2X's port injection its own dedicated low-pressure fuel system, separate from the factory main pump.

Once a car runs port injection alongside its factory direct injection, the usual approach is to push more fuel through the existing low-pressure system. The problem is that the factory pump is controlled by a PWM controller that pulls output back down once it hits target fuel pressure, and the high-pressure pump dumps fuel back into that same low-pressure system in pulses, causing pressure oscillation that the car's direct-injection system has to keep correcting for. A dedicated AFS sidesteps that entirely: it's a standalone low-pressure circuit built only to feed port fueling, with its own pump, filter, and adjustable regulator.

Why a Dedicated AFS


Fuel pressure stays stable regardless of what the main DI fuel system is doing
Pressure can be scaled 1:1 with boost
Smaller injectors can be run at higher resolution while still flowing more fuel than larger injectors on the stock system
Less correction demand on the car's factory DI fueling
Simplifies tuning of the port injection side


Construction


Billet aluminum top hat with 3 high-flow fuel ports
Fully adjustable, 1:1-scaling billet fuel pressure regulator
10-micron, USA-made Microglass fuel filter, rated for E85
Smooth-bore, high-flow PTFE AN6 feed and return lines
Billet fittings on all fuel line and top-hat connections
Plug-and-play connectors inside and outside the top hat, with AN8 fuel-rail adapters included, so the factory harness does not need to be cut or spliced
Configurable pump activation harness
100% ethanol-compatible components
Compatible with a stock or upgraded primary (DI) fuel pump


Choosing a Configuration



Model
MPN
Pump(s)
Combined Flow


AFS.425
601-0281
1x Walbro 450
425 LPH @ 3 bar


AFS.460
601-0282
1x Walbro 535
460 LPH @ 3 bar


AFS.640
601-0283
2x Walbro 450
640 LPH @ 3 bar


AFS.745
601-0284
1x Walbro 450 + 1x Walbro 535
745 LPH @ 3 bar


AFS.800
601-0285
2x Walbro 535
800 LPH @ 3 bar



These kits are designed for a port injection setup with the fuel rail mounted above the manifold. If you're running a plate-style spacer PI system, contact your BMP Tuning rep to confirm compatibility before ordering.

What's Included


Billet top hat with adjustable 1:1 fuel pressure regulator
Dedicated fuel pump(s) for the selected configuration
10-micron Microglass fuel filter
PTFE AN6 feed and return lines
Plug-and-play wiring harness and AN8 fuel-rail adapters


Installation Notes


Plug-and-play connectors mean the factory harness does not need to be cut or spliced for installation
If your tuner wants solid-state relay control, a separate relay kit is needed per pump; a two-pump configuration (AFS.640, AFS.745, or AFS.800) needs two relay kits
Professional installation and tuning by someone experienced with port injection systems is recommended


Product Specifications



Manufacturer: Precision Raceworks

Recommended Base Pressure: 43.5 psi-g

Maximum Fuel Pressure: 110 psi-g

Fuel Output Ports: 2

Fuel Return Ports: 1

System Weight: 11 lbs (single-pump configurations) or 14 lbs (dual-pump configurations), including lines and harness


Frequently Asked Questions

Do I need to cut my factory wiring harness to install this?No. This system uses plug-and-play connectors and included AN8 fuel-rail adapters, so no cutting or splicing is required.

Which configuration do I need?It depends on your port injection fuel demand and tune. Contact your BMP Tuning rep or your tuner to confirm the right AFS size for your build.

Does this replace my main fuel pump?No. It's a dedicated, standalone system for port injection only, and works alongside your stock or upgraded primary DI fuel pump.

Is this compatible with E85?Yes. Every component in the kit, including the filter media, is rated for 100% ethanol.