Click here to download installation instructions (PDF)
For installation on older 20-069X-XX FCST versions, click HERE.
For installation on older 20-049X-XX FCST versions, click HERE.
For installation on older 20-014X-XX FCST versions, click HERE.
To configure a complete fuel cell with FCST and other accessories, click below:
BACKGROUND
Since 2010, external Radium Engineering fuel surge tanks have been an excellent way to eliminate fuel starvation that occurs in racing. To simplify plumbing and packaging, in 2013 Radium Engineering introduced the first to market Fuel Cell Surge Tank (FCST) to the competition vehicle market. It quickly became the preferred fuel system for professional racing.
In 2023, the FCST-X was released. For more information regarding the FCST-X, click HERE.
WHAT IS A FCST?
The Fuel Cell Surge Tank is a drop-in fuel pump system for Radium Engineering's popular fuel cells or any cell that uses the industry standard 6x10 24-bolt fill plate bolt pattern. The FCST is designed to protect EFI vehicles that experience fuel starvation. It is NOT a glorified trap door box with baffles. It features a true dual-chamber fuel tank utilizing a single lift pump and up to 3 surge tank pumps all packaged inside the fuel cell. It provides all the benefits of a traditional external fuel surge tank without safety concerns and plumbing complexity.
IS THIS COMPATIBLE WITH MY FUEL CELL?
To install a Radium Engineering FCST into a fuel cell, the following criteria must be met:
1. The cell must have the industry standard 6"x10", 24-bolt flange opening.
2. The opening must be on the top face of the fuel cell (i.e. not a side face).
3. The cell depth must be at least 7.7" (196mm) measured from the outer top face to the internal bottom face.
HOW IT WORKS
A lift pump scavenges fuel from the bottom of the fuel cell and pumps it into the 2L surge tank. Inside the surge tank canister, up to 3 EFI fuel pumps can be used to feed high pressure fuel to the engine. If the lift pump starves, the volume inside the surge tank canister will keep the surge tank pumps fed and the engine supplied with fuel. The return from the fuel pressure regulator is also routed to the surge tank canister to help keep it full. 
As shown above, there are 3 fill valves integrated to the bottom of the surge tank. These 1-way FKM fill valves are sealed shut unless the fuel level in the cell rises above the fuel level in the surge tank. If this happens, each fill valve opens and sends 355LPH of fuel (1065LPH total) into the surge tank until fuel level reaches an equilibrium.
Excess fuel in the surge tank simply overflows back into the fuel cell. This dynamic sequence is all done inside the safety of a fuel cell.
FEATURES
Over the years, Radium Engineering has continued to refine the FCST into a robust and highly functional piece of hardware.
-Merged single 10AN ORB female threaded outlet. All pumps use check valves that prevent back-flow in multi-pump applications.
-One-way fill valves located on the bottom of the canister allows fuel in, but not out, keeping the surge tank full.
-Multiple fuel pump options including gerotor, turbine, and brushless DC motor pumps.
-Hermetically sealed high-current stainless steel electrical studs capable of handling all pumps.
-Simplified servicing eliminates sealing washers and fuel cell retaining brackets.
-Full CNC aluminum construction with anodized surfacing for superior corrosion resistance.
-Fuel compatibility: leaded and unleaded gasoline, methanol, ethanol, E85, etc.
-Rollover vent valve protection.
-Optional fuel surge tank level switch and diagnostic LED failsafe port (shown below).
STANDARD FITTINGS
PUMP OUT, 8AN MALE
The fuel pump outlet port is signified by the "PUMP OUT" engraving. It uses 7/8"-14 threads making it compatible with all 10AN ORB fittings. The FCST comes standard with a common 10AN ORB to 8AN male adapter fitting. However, various 10AN ORB adapter fittings can be purchased separately HERE.
RETURN, 6AN MALE
The external "RETURN" port is used for low pressure fuel returning from the FPR. This port uses 3/4"-16 threads making it compatible with all 8AN ORB fittings. The FCST comes standard with a common 8AN ORB to 6AN male adapter fitting. However, various 8AN ORB adapter fittings can be purchased separately HERE.
VENT, 8AN MALE
The "VENT" port is tapped with 1-1/16"-12 threads making it compatible with all 12AN ORB fittings. The FCST comes standard with 20-0934 which uses a common 8AN male outlet fitting for standard fuel filling. However, 20-0535 can be purchased separately with a 12AN male fitting for quick fill dry break systems that require a high-flow vent.
WHATS IN THE BOX?
The following comes standard with every FCST variation
-8AN roll over vent valve
-6x10 24-hole FKM gasket
-6AN male return fitting (other sizes sold separately)
-8AN male pump out fitting (other sizes sold separately)
-Fuel level sensor block-off plate
-Fuel level switch block-off plug
-Three FKM 1-way fill valves
-Stainless steel mounting hardware
-Insulated anodized aluminum acorn nuts
-Electrical power wire ring terminals
-Links for compatible fillers (not included), Direct Mount or Remote Mount
SELECTING YOUR FCST
The different FCST part numbers are based on the brand and quantity of fuel pumps. When determining a fuel pump configuration, select a combination that can support the engine output. More fuel pump information can be found HERE.
If you would like to use a different pump, please contact Radium Engineering technical support.
20-099X-XX FCST
The 20-099X-XX Fuel Cell Surge Tanks utilize new design features that reduce overall weight by 35.3%. These new additions also improve assembly time. They also use stronger stainless steel lift pump mounting brackets. Furthermore, they are compatible with Radium Engineering's shrouded fuel level sensors.
FCSTs are available with and without fuel pumps included. The lift pump is always matched to be the same style pump(s) found inside the fuel surge tank canister, with exception to the brushless Ti Automotive E5LM variation (below). Any option that lists "Pump Included" comes pre-assembled with new fuel pumps and filters installed.
If "pumps not included" is ordered (shown above), fuel pumps must be sourced separately. A filter sock will only be required for the lift pump as inlet filters are already supplied for the surge tank pumps. Also, there will be enough components included with this option to use up to 3 pumps in the surge tank. Depending on the setup, some parts may not be used.
20-0693-00 FCST, PUMPS NOT INCLUDED, BRUSHLESS TI AUTOMOTIVE E5LM
The 20-0693-00 Fuel Cell Surge Tank is only available without pumps included. It is designed to use one or two Ti Automotive E5LM brushess fuel pumps inside the surge tank. A standard brushed pump is used as a lift pump.
Ti Automotive E5LM brushless fuel pumps can be purchased HERE, but will not be installed by Radium Engineering. Assembly must be performed by the user. 
As shown below, the lift pump electrical and plumbing is set to be compatible with Walbro F90000267/274/285/295 fuel pumps. Radium Engineering recommends the Walbro F90000295 as a lift pump for maximum flow with a 14-0143 Filter Sock. Filter socks are required for all pumps. 
NOTE: Ti Automotive E5LM brushless fuel pumps do not have integrated check valves like many other pumps.
So this FCST includes two 20-0598 fuel pump outlet adapter check valves (shown above). Because the 2 surge tank pumps merge into a single outlet collector, these high flow 1-way valves permit multiple pumps to be staged without backflow.
20-0695-00 FCST, PUMPS NOT INCLUDED, EXTERNAL PUMPS
The 20-0695-00 Fuel Cell Surge Tank is only available with pumps not included. It is designed to be used with inline electric pump(s) or a mechanical fuel pump. One or two -10AN (5/8") fuel pickups are used inside the surge tank. Each pickup uses a 100u (micron) filter. If two pickups are used, 20-0737 Distribution Block is recommended for pumps that use a 12AN inlet.
The lift pump electrical and plumbing for this kit is set to be compatible with Walbro F90000267/274/285/295 fuel pumps. Radium Engineering recommends the Walbro F90000295 as a lift pump for maximum flow with a 14-0143 Filter Sock.
WHAT ELSE IS NEEDED?
FUEL CELL
A fuel cell is NOT included with the FCST. The fuel cell MUST use a 6x10, 24-bolt fill plate flange. The distance from the outer top face to the internal botton face must be at least 7.7" (196mm). The distance from the top of the fuel cell to the bottom of the lift pump filter (lowest point of the kit) is adjustable. However, if the fuel cell is deeper than 9" (229mm), click HERE.
FUEL FILLER
The fuel filler pattern uses an industry standard 6-bolt (2.18" B.C.) flange. Radium Engineering has them for both direct filling and remote filling.
VENT HOSE
A hose and/or filter must be connected to the "VENT" port fitting. For compatible vent kits and more information on how these are plumbed and routed, go HERE.
OPTIONAL ACCESSORIES
FUEL LEVEL SENDER
The FCST comes standard with a fuel level sender block-off plate. However, SAE fuel level sensors of various lengths can be purchased separately HERE.
FUEL LEVEL SWITCH / DIAGNOSTIC INDICATOR
These FCSTs come standard with a 2AN ORB plug preinstalled in the "level switch" port. For information on adding a fuel level switch and diagnostic indicator, click HERE. This little device provides a warning when the fuel level inside surge tank canister drops by 20% or more.
NOTE: RADIUM DOES NOT OFFER A WARRANTY ON ANY FUEL PUMPS! FUEL PUMPS CAN BE RETURNED IN UNUSED CONDITION WITHIN 30 DAYS OF PURCHASE. SEE TERMS AND CONDITIONS FOR MORE INFORMATION.