Fuel Pump Performance Test – Walbro, Bosch 044, Aeromotive, AEM vs Deatschwerks vs EVO 9 vs STI & more


Fuel pumps included in the test Walbro GSS342, Fake Walbro, No name 340lph, Bosch 044, Fake 044, Aeromotive Stealth 340, CNT Racing, Deatschwerks DW300, 05 STI Stock Unisia, EVO 9 Stock Denso, AEM 320

This article is based on data from a performance fuel pump group test done by Import Tuner magazine. You can read their fuel pump test here & part 2 here

DISCLAIMER: The power figures in the supplied graph are a guide only, they should not be treated as exact

First point to address is how much fuel pressure do you need from your fuel pump?

You need to add two things together.

First is the system pressure of your fuel system, ie the fuel pressure it is designed to run at and/or the fuel pressure it has been tuned with.

To this number, you add the boost pressure.

If you want to get the fuel out of the injector at 45PSI and there is 30 PSI of boost pressure to overcome, you need a total fuel system pressure of 75PSI

To use the graph, find your total fuel pressure along the bottom, and then go up to find the pump that meets the power output your engine makes.

It is probably a good idea to put some room to manoeuvre, so add 20% to your current power level if you wont be making changes to the car later.

If you plan to add another 100bhp to the engine later, add your current power + the 100 bhp + 25% for the total power capability you need from your fuel pump.

In reality, all of the performance fuel pumps tested by Import Tuner magazine will be sufficient for 90% of cars, expect for the one fuel pump which is noticeably worse than the rest.

Fuel Pump Group Test – Original fuels pumps, do you really need something better?

In the graph you can see the fuel pumps supplied on the EVO 9 MR and on the 2005 Impreza STI

All of the fuel pumps tested improve on these fuel pumps.

The standard EVO fuel pump draws around 11 amps in normal driving

The standard STI fuel pump draws around 8 amps in normal driving

You can see that the original fuel pumps are severely limited when you start turning up the boost.

Fuel Pump Group Test – Some things to note about the results.

Power consumption

All of the pumps in the test are going to be drawing 13-14 amps minimum in most driving conditions. You may need to beef up the cables running to your fuel pump so the pump is getting the power it needs.

There are two exceptions.

The worst performing pump in the test also draws less current (at least it has something going for it…)

But drawing even less current is the Walbro 255 pump.

Maximum current draw on the Walbro and 100 PSI is only 10 amps, compared to 15-16 amps for the other fuel pumps in the test.

At 60 PSI fuel system pressure, the Walbro 255 needs about half as much current as the rest of the pumps in the fuel pump test.

In short, the Walbro is the most efficient fuel pump in the test on an bhp per amp basis.

If you crank up the current draw you can increase fuel flow

If you crank up the current draw you can increase fuel flow


Fuel Pump Group Test – The fake Walbro pump looks good!

On paper the fake Walbro seems to perform well but during the testing two issues came up which relegated the pump to the bottom.

The first is the current draw. For similar fuel flow to the genuine Walbro, the fake Walbro was drawing almost twice as much current.

The second was the stability of the current demand. It was very difficult to keep the pump operating at a constant fuel pressure, this will cause rapid changes in the fuel pressure at the injector, not having consistent and predictable amounts of fuel going into the engine is not good for power/economy. Apparently this is a common problem with these pumps.

Fuel Pump Group Test – The winner

For cars making up to 500bhp with up to 2.5 bars of boost, or for cars making up to 550bhp on 2 bar of boost,  the Walbro is the clear winner. It will probably require zero modifications to the electrical system, ie it will not need thicker wires running to the fuel pump.

It is an OEM like fuel pump upgrade. Drop it in an go.

What if you are running more power?

The other pumps in this test will handle around 75 bhp more than the Walbro for the same boost level but they will probably require new cables to be run to the fuel pump to support the potential current draw.

But there is one stand out fuel pump and that is the Bosch 044. 

Import Tuner say it uses older technology but it is still getting the job done. The only issue being the size of the pump, it is a different size to most standard fuel pumps (the other pumps in this test are designed to be “drop-in”).

To use the 044 fuel pump, you may need to modify your current fuel pump holder or mount the pump externally, either way, there will probably be work involved.

But if you need 650 bhp fuel support the 044 is the way to go.

Fuel Pump Group Test – Summary

The moral of the story seems to be, if you are a manufacturer of fuel pumps, increase the amount of amps your fuel pump can draw if you want to increase fuel flow, end of conversation.

There does not appear to be any difference in the technology between the fuel pumps, at least not a big difference. The difference in the fuel flow between the pumps seems to be based solely by the amps that the pump can consume.

The one exception to the rule being the Walbro 255 fuel pump. This pump draws less current than the original STI and EVO fuel pumps and yet flows considerably more fuel. On the surface at least, Walbro does appear to be doing something different with the technology inside their fuel pump compared to the other manufacturers in this test.

Up to 500-550 bhp with original fuel pump electrical cables and fuses, go with a Walbro. It is a drop in solution.

If you need more fuel flow than the Walbro can supply, it is probably a good idea to rewire your fuel pump with larger cables. Fuel pump fuses tend to be in the 10-15 amp range. Just in normal driving the other pumps in this test are going to be drawing 12 amps+, (the Walbro only 6 amps) and 14 amps plus at full power.

Personally, if I am going to invest the time to rewire my fuel pump, I think I’m going to do that bit extra and install the 044 with its own swirl tank

In short, up to 500bhp, Walbro 255, more than that, an 044 in its own swirl tank.

Street & Circuit Shop

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