As part of our Fuel Surge Tank (FST) line, Radium Engineering carries various fuel pumps from select manufactures that differ in flow rates. Third party independent flow testing data on these pumps can sometimes be found with research on the web.  However, the data can be inconsistent between sources, presented in a way that makes comparison difficult, or may not exist at all.  This makes it hard to compare pumps directly. To remedy the issue we decided to do our own in-house back to back comparison test of all six fuel pumps we currently offer with our FST product line. This information would equip us and our customers with the knowledge to correctly choose a specific Radium FST.

The test measured pressure, flow rate, voltage, current draw, and sound level. The sound was measured in decibels (dB) using the sound level meter below...

For some customers building street cars, fuel pump noise is an important aspect. This test would give a good comparison between all the pumps.

Shown below are the six fuel pumps that were tested. All units were brand new off the shelf.

Top Row: Bosch 044 (External Pump), Bosch 040 (Internal Pump)
Bottom Row: Walbro 400 E85, Walbro 400 Gas, Walbro 255, Aeromotive 340R

The flow test used a simple controlled orifice. The fuel pump line was restricted by the orifice until the desired line pressure was achieved and then flow was tested using a timed interval. The volume of fluid the pump output during the timed interval was measured to provide the volume per unit time (flow rate) at each line pressure.  As always, Mineral Spirits (specific gravity of .76) was used for the testing fluid. We are aware that there are more accurate (and expensive) ways to flow test fuel pumps, but this setup was adequate for us to compare the fuel pumps in identical test conditions. Also, note that these results should not be compared to other tests, since our test setup is inherently unique. So lets get to the results.

Flow Rate

Note: To convert to PSI, just multiply the Bar pressure by 14.5

The above chart shows the new Walbro 400 and Walbro 400 E85 have superior flow when compared to the others, even the "mighty" Bosch 044. One interesting note is that unlike the other pumps, the two Bosch pumps maintain flow level extremely well as pressure increases.

We generated this table as a rough guide to use when estimating the Horsepower supporting capacity of the fuel pumps. This guide is approximate and there should always be a built-in safety factor when selecting the pump.

Current Draw

Looking at electrical current, one can almost make the assumption that the more current the pump draws, the more it flows. The high flowing Walbro 400 pumps draw close to 20Amps at 6 bar! There are a couple exceptions to this though. For instance, the Aeromotive pump required more current than the Bosch 044, but flowed less than it.

The sound level was measured inside the main 5 gallon fuel container. All pumps were fully submerged in the testing fluid. The sound level (shown below) was the average of two readings taken at low and high pressure. Sound is highly sensitive variable and can be influenced greatly by the surroundings, this required extra effort on our part to maintain precise consistency during each sound measurement.

The Walbro 255 takes the prize as the loudest pump followed by the Bosch 044. It is interesting to note that the highest flowing pump in the group (Walbro 400 E85) was also the quietest.
Keep in mind that many factors effect real world pump noise levels in the vehicle and are not reflected in this test. Also, while the Walbro 255 was the loudest in this test batch of pumps, there are many aftermarket branded fuel pumps not included in this test that are considerably louder and do not flow much more, if at all.

So now lets talk value. A certain fuel pump may flow well, but if it costs 5 times more than one that comes close, what is the point? Below is a chart that shows flow per dollar. Note: We used retail prices for all pumps.

The chart shows that the Walbro 255 gives the most flow per dollar spent. In fact, all the Walbro pumps show to be good value. Due to their high price, the two Bosch fuel pumps are not as good a value.


Walbro 255:

Excellent value and proven reliability in a small package. While the loudest of the batch, it is still an OEM quality pump so it is all relative. These pumps are used extensively all over the world and are "hands-down" the most popular in the aftermarket world.
Single Walbro 255 FST
Dual Walbro 255 FST

Bosch 040:
A low current drawing OEM Audi pump with a Bosch badge that offers consistent flow across a wide pressure range. Note: The low current draw will help keep fuel temperatures down. 
Bosch 040 FST

Bosch 044:
This age-old design used on classic Porsche and Ferrari still holds its ground quite well, but its high price and high noise level keeps it from being the best.
Dual Bosch 044-Horizontal FST
Dual Bosch 044-Vertical FST

Aeromotive 340R:
This compact high-current drawing pump heated up our test fluid quite quickly, but also performed quite well and has a reasonable flow per dollar value.
Single Aeromotive 340R FST
Dual Aeromotive 340R FST

Walbro 400 Gas/E85:

These new pumps from Walbro perform extremely well on all fronts; flow, noise level, and value. They set a new bar for flow from a compact package. Just make sure your wiring can handle 20A of current!
Walbro 400 Gas/E85 FST

We hope this information will assist our customers when considering what pump to use with their surge tank.
Radium Fuel Surge Tanks