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Radium Fuel Surge Tank - Fuel Hanger (FHST) BMW

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Product Description

The Radium Engineering fuel surge tank hanger permits the use of 1, 2, or 3 aftermarket high pressure pumps and 1 lift pump in the stock Mazda FD RX7 fuel tank. It is compatible with following models:

The unique integrated 1.85L surge tank completely eliminates fuel starvation. The system also permits the use of high flow aftermarket fuel pumps. No grinding, bending, or modification of the trunk floor sheet metal is required.

This system is compatible with the following fuel pumps:
Walbro F90000267
Walbro F90000274
Walbro F90000285
Walbro GSS342 255lph
AEM 50-1220

To simplifying aftermarket -AN hose plumbing, the 10AN ORB threaded feed port features a low profile 8AN male fitting and the 8AN ORB threaded return port features a low profile 6AN male fitting. To reconnect the OEM feed and return hoses, barb fittings are also included.

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

Integrated Surge Tank
A fuel surge tank (FST) is the best solution in preventing fuel starvation. Since 2009, Radium Engineering has been designing numerous FSTs for multiple applications. But after some sanctioning bodies banned externally mounted FSTs, Radium built the first production fuel cell with an integrated surge tank (FCST). Because the FD RX7 can experience high lateral Gs, it inherently suffers from fuel slosh. Fortunately, Mazda manufactured a gas tank with a very large bolt flange pattern (similar to the FCST) permitting various upgrading options.

For a proper FST to function, a lift pump is necessary to maintain volume within the surge tank. This lift pump is located in the rear portion of the OEM sub tank within the Mazda gas tank. Included in the kit is a lift pump mount that snaps onto 3 sides of the OEM sub tank. It also serves as a baffle keeping the lift pump supplied with fuel. Measures were taken to ensure that the lift pump always has fuel to deliver to the surge tank.

The 1” check ball allows fuel into this tight area during acceleration (above) and traps fuel in during deceleration (below).

The lift pump sends low pressure (high volume) fuel in the FST through a special deflector in the bottom of the surge tank canister. The 24 hole diverter evenly disperses fuel inside the canister preventing air bubbles and foaming. When a low demand for fuel is present, the canister will overflow back into the OEM sub tank.

For the high pressure pumps supplying fuel to the engine, a bespoke stainless steel triple pump mesh strainer is included for proper inlet filtration.

Because all compatible fuel pumps utilize integrated check valves, the high pressure pump outlets merge into a single 10AN billet collector.

The returning low pressure fuel from the regulator is sent back into the FST keeping it full. A second 24 hole deflector is used in this location further preventing air bubbles and foaming. All of this happens inside the OEM gas tank.


  • Drop-In OEM Replacement
  • Permits 1-3 Surge Pumps plus 1 Lift Pump
  • 8AN Male Pump Outlet Fitting
  • 6AN Male Return Inlet Fitting
  • Fuel Starvation Protection
  • High Current Electrical Hardware
  • Compatible with Various Pumps
  • Anodized Aluminum Construction
    -Gasoline and Ethanol Compliant

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