Testing the Radium Fuel Surge Tank

After countless CAD models, design revisions, rapid prototypes, a custom aluminum extrusion and working with our machinists, we have our first batch of Fuel Surge Tanks (FST). The FST is designed to augment a factory fuel system. It works by ensuring a constant and reliable supply of fuel to the engine under all conditions. Each fuel surge tank contains a high performance fuel pump that provides extra fueling capability.
Exploded view showing Fuel Surge Tank with internal fuel pump

Before releasing the system for sale, we thoroughly tested the device. A concern for the FST design was the potential heat that could transfer to the fuel from the internal fuel pump. Our testing was to see if the surge tank would act as a fuel heater.

The (raw aluminum) prototype, fully assembled and ready to test

Testing utilized two different fuel system configurations to evaluate and compare results. The first setup used the Radium FST with an internal Walbro 255lph pump. The second setup used an external Walbro 255lph pump without a surge tank. Both tests used white spirit as the working fluid. White spirit is a commonly used solvent found in fuel injector and fuel pump cleaning processes and has similar properties to gasoline. The minimal use of only 1.5 gallons of fluid would simulate a low fuel condition and make temperature changes more immediate.

Fuel Surge Tank plumbed for testing

We chose to operate our high pressure line during both tests at 4Bar (~58 psi) using a Radium Fuel Pressure Regulator. This pressure was selected to fully load the pump to create the worst case scenario where the pump is exerted to the maximum work load and heat levels peak.

High pressure line entering regulator (blue fitting), temperature probe plumbed into opposite side port

Ambient temperature was recorderd and was within 1 degree C during all tests. Fluid temperatures were monitored at the same locations in both setups and were measured using thermocouples in the reservoir(T1) and in the high pressure line(T2) via a port on the regulator.

Power was supplied to the pumps using a 12V battery with an attached variable rate charger. This allowed constant voltage with varying electrical loads. The tests ran at a steady 12.3V and temperatures were recorded every 5 minutes for 90 minutes.


The first test used the Radium Fuel Surge Tank setup (shown below). In this test, the high pressure line that normally feeds the fuel rail and injectors is sent directly to the fuel pressure regulator and returned to the FST.


Test Setup 1. Utilizing Radium Fuel Surge Tank (Blue)


The second test consisted of the same basic set-up. This time the reservoir's pump fed an external (in-line) Walbro 255lph pump (shown below) rather than the Radium FST. This eliminated any heating effects from the external surface of the pump.

Test Setup 2. Utilizing a Walbro external pump

The results were quite surprising.  We speculated that the FST internal fuel pump would transfer more heat to the fluid due to its submersion.  The results strongly proved otherwise...

The chart above shows the fluid temperatures (average of T1 and T2) over time. It is clear that having the pump internal to the Fuel Surge Tank (blue line) does not excessively heat the fuel. In fact, it appears that the FST might provide some extra cooling that does not occur with the external pump (red line).
The yellow line represents a single pump in the reservoir using the same fuel pressure regulator, which simulates the factory fuel system.The green line shows the ambient temperature.

These results show that over 90 minutes the fluid temperature increases 20-30 degrees celcius. This will not have any noticeable effect on engine performance. Fuel density only decreases by roughly 2%. When considering the air/fuel ratio, there is typically 12 times more air than fuel in the cylinder which would make any effects even more inconsequential.

Based on the test results, we are confident about releasing our Fuel Surge Tanks for sale. We will be releasing FST kits for specific vehicles and applications. We will also have FST that utilize other popular fuel pumps including the Bosch 040 and Bosch 044.

We will be publishing a more detailed informative blog entry on the FST very soon.
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