How does the flow of a Bosch 044 fuel pump compare to a Walbro 255HP?
Independent test results show the where the popular Walbro 255HP fuel pump flows 256 LPH at 30 psig 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. An interesting fact is that the Bosch 044 at 90 psi is flowing about as much the Walbro 255HP at 30 psi.
