How does the flow of a Bosch 044 fuel pump compare to a Walbro 255 Lhp?

Independent test results show where the popular Walbro 255HP fuel pump flows 256 LPH at 30 psi fuel pressure, then Bosch 044 flows 290 LPH.

This isn't really important though because most cars only see this pressure at idle.

Now assume a vehicle running 30psi boost on 45 psi base fuel pressure (75 psi net fuel pressure).

At this pressure the Walbro 255HP is flowing 208 LPH and the Bosch 044 is flowing 267 LPH (28% more capacity).

Finally, at the top end of the chart (90 psi fuel pressure) the Walbro 255HP flows 156 psi and the Bosch 044 flows 253 LPH, which is 62% more!

This graph illustrates how the Walbo 255HP fuel pump has an exponential decline in flow at higher pressures, where as the Bosch 044 is linear in comparison



An interesting fact is that the Bosch 044 at 90 psi is supplying the same quantity of fuel the Walbro 255 does at only 45 Psi.

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Any infomation on a bosch 910?

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Honda Hannspree Edition CBR 600 RR - SOLD
Yamaha FZ1N - Purchased

Just for you bud:

Each Bosch 910 fuel pump provides 130LPH of flow and operate at 72.5 PSI.

Bosch 910 Fuel Pump Specs:
Bosch Part Number: 0 580 254 910
Minimum Current: 12 Volts
Operating Pressure: 72.5 PSI (5 Bar)
Minimum Flow @ Outlet: 34 GPH (130 LPH)

Fuel Pump Connections:
Inlet: 15MM
Outlet: M12 x 1.5
Electrical: Positive M5 / Negative M4

It's a baby compared to the 044! (see below)

Each Bosch 044 inline fuel pump provides 300LPH of flow and operate at 72.5 PSI.

Bosch 044 Fuel Pump Specs:
Bosch Part Number: 0 580 254 044
Minimum Current: 12 Volts
Operating Pressure: 72.5 PSI (5 Bar)
Minimum Flow @ Outlet: 80 GPH (300 LPH)
Fuel Pump Location: In-Line
High Temperature Reduction: 8 GPH (30 LPH)
Weight: 1030 Grams (2.27 Pounds)

Fuel Pump Connections:
Inlet: M18 x 1.5
Outlet: M12 x 1.5
Electrical: Positive M6 / Negative M5

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Very interesting. I knew that the Bosch is a better pump but that's a pretty big difference! So there is a reason to put up with the extra noise haha.

Correct me if I'm wrong but you would only notice a difference between the two on heavily modified / high flow applications, right? Ie: it doesn't matter how much more than 100lph they flow if your injectors only spray 100lph? The key is to prevent fuel pressure drops and not overload your fuel pump to the point of failure?

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MY99 WRX (Sold)
MY06 WRX 241hp 430nm atw (Sold)
MY09 BMW 135i 247kw atw (Current)

Hmmm interesting. The 910 does seem very small in comparrison. Wonder if im starting to punch for the 250kw+ if its going to cause issues. Spose we'll see :P thanks Rosso.

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Honda Hannspree Edition CBR 600 RR - SOLD
Yamaha FZ1N - Purchased

it's all about headroom in regard to pressure v flow.

have you read about pot#4 going lean on the oem system?

The fuel absorbs heat from the rails, injectors and lines under the manifold...hot fuel is less dense = slightly leaner mixtures in pot # 4.
The higher the flow through the rail the lower the heat picked up by the fuel, the lower the chance of the last injector on the fuel rail loop leaning off through latent heat absorbtion.....Apparently!

440cc/minute sti injectors x 4 = 1750 cc/m wide open...that's a fair bit of fuel to move with zero pressure drop.

plus on boost the pressure is rasied to keep the fuel pressure in the rail a set amount (1 psi higher for every 1 psi of boost iirc).

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Thanks for the explanation RS! I have heard about cylinder 4 running lean on the stock system. I've also heard that a manual boost controller magnifies this problem - is this due to the same reason (hotter fuel, not compensating for boost)?

Just for the people out there, you can get a Walbro online (if you're game) for around $160 and that's all you need to do the install. The Bosch can be acquired for $260 and how much more are the required fittings? And is the Bosch really that loud? (my Walbro is pretty much silent - have heard it prime a couple of times when I've had the window down in the garage at start up).

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MY99 WRX (Sold)
MY06 WRX 241hp 430nm atw (Sold)
MY09 BMW 135i 247kw atw (Current)

The Bosch's vary.. some are quiet, some aren't.

The Bosch 044 fits with a bit of cutting of the feed tube, and either running a universal fuel sock or modifying the stock one to fit (via threading it into a speedflow fitting or running a rubber hose between it and the pump), as well as an outlet fitting and a piece of bigger hose to suit. It needs to be rubber mounted with nitrile rubber to keep the noise down too.

I’m running an 044 now but am going to a Walbro GSS342 because its much quieter. If I ever need the fuel capacity (and I don’t think I will with my power targets of 350-360 at the hubs), I’ll go with an external 044 mounted under the car with one of those ProcessWest surge tank setups.

is this going to be happening soon? i sense a driveway thread/update!!!!

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JDM version 3 STi RA