RE13REW

I have a goofy question about aftermarket fuel pump, i don't understand the PSI for the fuel pump; actually what is the meaning of the PSI in the fuel pump, is that mean the max psi it can pull at 13.5 volts ? or something ???

How about 255lph @80psi @ sth volts ???? will that happen ???
Will that be more PSI when my boost goes up ???
information from internet:
255 lph @ 40 PSI @ 13.5 volts - Wallbro 255 fuel pump
290 lph @ 42 PSI @ 13.5 volts - Supra fuel pump
230 lph @ 71 PSI @ 13.5 volts - Supra fuel pump

CCarlisi

The pressure reading refers to the psi that the pump's volume output is measured at. For example, the walbro 255 can move 230lph when the pump is fighting against 40psi of line pressure measured at the pump output. To compare the walbro to the supra pump the pressure would have to be raised to 71psi.

There are a couple factors to take into account when deciding what pressure to look at.
(1) The desired fuel pressure gradient (note, not simply fuel pressure). Most people use 40psi. The higher this number is the more fuel comes out with each duty cycle.
(2) Fuel line resistance. According to Max Cooper's trusty fuel system calculator there is approximately 15psi of fuel line resistance in the stock system. Therefore, for the injectors to see 40psi the pump must output 55psi.
(3) Manifold pressure/vacuum. If the goal is to have a pressure gradient of 40psi, then when the manifold is pressurized to 15psi the fuel pressure must be increased by 15psi to maintain the original gradient of 40psi. [(40+15)]-15psi=40psi. When the car is in vacuum the reverse happens. At idle my fpr drops the pressure by about 8psi to 32-33lbs.

Eg:
I have 550 primaries and 1680 secondaries. I'm running a pressure gradient of 40psi with a relatively mild afr. I do not want to exceed 85% duty on my injectors. The maximum amount of boost I want to run is 15lbs. According to Max's calculator I need a fuel pump that flows 218L/hr at 70psi (40psi gradient+15psi max boost+15psi line resistance).

Therefore, for my car I want to know the output of the above pumps at 70psi.

Hope this helps.