Radium Engineering RA Fuel Hanger Surge Tank BMW E90/91/92/93 -GSS342 - 20-1970

Pumps

20-1972 FHST, BMW E90/91/92/93, Walbro GSS342 or AEM 50-1200

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 FST canister keeping it full. A 6-hole diverter evenly disperses fuel inside the canister preventing air bubbles and foaming. Also, 2 fuel return orifices are included for fine-tuning the desired fuel pressure to the fuel pumps' flow rate.

Pump Compatibility

20-1972
Walbro F90000267
Walbro F90000274
Walbro F90000285

20-1970
Walbro GSS342 255lph
AEM 50-1200

Note pumps are not included - must be purchased separetly

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(s) and Fuse(s)

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)
NOTE: 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.