The Radium Engineering Fuel Cell Surge Tank (FCST) was a revolutionary product when it was first released in the Fall of 2014. Since then, the FCST has found it's way into many successful competition vehicles. The ability for it to eliminate fuel starvation during aggressive driving has made the FCST ideal for any motorsports application. It has become the go-to standard for professional drift teams and has proven itself time and again in many race and street applications worldwide. The Radium FCST continues to be the ONLY true multi-pump dual-chamber surge tank solution that installs INSIDE a competition fuel cell. 
The four year anniversary was a chance to update the design and make some small changes that will improve the functionality and reliability of the FCST. 


The FCST has previously used two circular electrical connectors, as shown below. One for the lift pump and one for the primary pumps.

The new version has eliminated the circular connectors and associated flying-lead harnesses and replaced them with individual stainless steel electrical stud connections, as shown below.

The design of these electrical studs has proven reliable through in-house testing and over the past few years on Radium's line of in-tank fuel pump hangers. The studs offer easy and inexpensive serviceability, easy troubleshooting and the ability to handle very high current loads. They create a hermetic seal with the top plate that is impervious to all fuel types. Another added benefit is the low-profile nature of the studs and the connecting wires, which allows direct and uncluttered wire routing. Crimp-on ring terminals and shrink tubing are included with the FCST.


The previous version of the FCST used individual 6AN male fitting for the pump outlets that feed the engine, as shown in the picture below. If less than three pumps were selected by the customer, a plug was used on the remaining port(s).

This setup required the use of hoses and T or Y fittings to combine the outputs together into a single line, creating plumbing complexity.
The new version utilizes a single output for all pumps. The top plate outlet port is female threaded for 10AN ORB and a 10AN ORB to 8AN male adapter is included by default (shown) for all configurations. Other compatible 10AN ORB adapters can be found HERE and purchased separately.

The merging of the pumps is done internally. Block-off plugs are included for configurations that require less than three primary pumps. All of the fuel pumps that Radium offers with the FCST have built-in check valves to prevent back-flow. This allows the pumps to turned on/off at different times based on engine fuel demand.


The vent fitting on the FCST plate plays a crucial roll of allowing air out when fuel is entering the fuel cell during filling, it also keeps the cell at atmospheric pressure.  Previously, the vent port was a 8AN ORB female port. The new version has been changed to a 12AN ORB female port, shown below. 

The new larger vent port allows air to escape faster for quick filling applications. This larger vent port also meant a new roll-over protection valve needed to be designed. A roll-over protection valve installs into the vent port and prevents fuel loss should the vehicle ever become inverted. It was decided that the new valve should not only offer roll-over protection, it should also prevent fuel loss in the event the fuel cell is over-filled. 

The Dynamic Safety Valve (DSV) was created (shown above) and performs two functions. First, it shuts off flow if inverted. And second, it contains a floating ball that seals the vent should the fuel level rise high enough, preventing fuel loss through the vent port. Another advantage to the new DSV compared to the previous roll-over protection valve is that it can be removed easily without the need to separate the top plate from the fuel cell bladder. The DSV is included by default with every FCST and retains the same 8AN male for vent hose attachment. This valve is to be used with standard filling only (not quick fill dry-break systems). 
Radium will introduce a high-flow DSV variation that will be suitable for quick-fill systems at a later date.


The machining of the underside of the FCST top plate was modified to better manage the flow of fuel into and around the surge tank. The return fuel now passes through a diverter that directs it tangentially into the surge tank canister, reducing fuel agitation and creating a true "swirl pot". Fuel from the lift pump also enters the surge tank tangentially for the same reasons.

  • The new FCST plate is still the same 6" x 10" 24-bolt size and will work in all previous applications
  • The same fuel pumps as before are still offered
  • The fill neck and level sender interfaces remain unchanged
  • Still E85 compatible
  • The FCST can still be ordered by itself or packaged with a competition fuel cell
  • Pricing remains unchanged

Additional Information
Click HERE to learn more about the fuel cells Radium offers
Click HERE to watch an independent fuel cell installation video
Click HERE for a fuel cell ordering guide