The Radium Engineering Fuel Hanger Surge Tank (FHST) is a drop-in aftermarket fuel pump solution for maximizing power potential.

The FHST system independently supplies fuel to the port injectors, while the direct injection system remains undisturbed using the OEM fuel pump.

The surge tank functionality ensures that a fuel reserve is kept trapped around the aftermarket fuel pump to prevent fuel starvation.

COMPATIBILITY

BMW E90 3-series (N54 or N55)

BMW E91 3-series (N54 or N55)

BMW E92 3-series (N54 or N55)

BMW E93 3-series (N54 or N55)

NOTES:

1. This system is also compatible with the E90/91/92/93 M3 fuel tank. However, because the M3 uses a brushless fuel pump, the installer must devise a solution for triggering the new surge tank fuel pump(s). This is not covered in the installation instructions.

2. This system is NOT compatible with BMW 1-series vehicles (E81/E82/E86/E87).

BMW Fuel Tank

The OEM saddle bag fuel tank is quite complex. The venturi jet pump is driven by the feed line instead of the return (M3 has 2 venturi jet pumps). The post pump filter and FPR are integrated into the LH side of the tank where the FHST mounts.

Radium FHST

When these BMWs experience high lateral Gs, they inherently suffer from fuel slosh. The FHST is the best solution in preventing fuel starvation. As described below, the FHST pump(s) are supplied with fuel from 3 different sources: the OEM electric "lift" pump, the fuel pressure regulator (FPR), and the integrated 1-way valve.

Note that the BMW fuel pump is still retained but is now repurposed as a "lift" pump to fill and maintain volume in the FHST. The lift pump fills the FHST canister through a special orifice in the FHST. This keeps the required pressure for the venturi jet pump(s) to be active and deliver fuel to the lift pump. When a low demand of fuel is present, the FHST canister will overflow back into the LH side of the OEM tank. Fuel will then cycle back into the FHST through a 1-way valve integrated to the bottom of the FHST. Unlike traditional surge tanks that rely heavily on surge tank pump and lift pump flow matching, the FHST uses an extra source that negates this important relationship. No matter what is dynamically changing with the other 2 fuel sources, the high flowing 1-way valve will constantly supply fuel to the FHST canister until the LH side of the gas tank becomes extremely low. At this point, it is up to the lift pump and the FPR to supply the last few ounces of fuel to the FHST. 

Integrated Fuel Pressure Regulator

Like OEM, a fuel pressure regulator (FPR) is integrated into the unit.

Furthermore, if an intake manifold signal is installed, this FPR can operate at a 1:1 ratio permitting fuel pressure to proportionally increase with boost pressure. The returning low pressure fuel from the FPR is sent back into the surge tank keeping it full. A 6-hole diverter evenly disperses fuel inside the canister preventing air bubbles and foaming.

Plumbing

To clear the OEM fuel pump cover plate, the 8AN ORB threaded feed port features a preinstalled low profile 8AN male fitting.

Electrical

The custom designed stainless electrical studs easily handle the high current demand that compact bulkhead connectors lack. These serviceable connections are properly sealed and impervious to all standard and exotic fuels. Nonconductive acorn nuts are provided to prevent any accidental short circuiting. Electrical hardware is included for the fuel pump(s) and OEM level sender. Furthermore, the in-tank wiring is insulated with high quality chemically resistant ETFE.

These kits include 1 relay, 1 fuse, and all associated wiring and hardware to install 1 surge tank pump.

If an extra fuel pump will be installed supplement with an extra relay and fuse.

20-1972 is compatible with the following fuel pumps:

Walbro F90000267

Walbro F90000274

Walbro F90000285

Features

• Drop-In OEM Replacement
• Permits 1 or 2 Surge Pumps 
• 1:1 Fuel Pressure Adjustments
• Fuel Starvation Protection
• Integrated 1-Way Fill Valve
• High Current Electrical Hardware
• Compatible with Various Pumps
• Anodized Aluminum Construction
• Gasoline and Ethanol Compliant
• Anodized Aluminum 8AN Male Outlet Fitting
• Anodized Aluminum Surge Tank Canister
• Fuel Resistant Tubing and Wiring
• Stainless Steel Hardware
• Relay and Fuse