Fuel line pressure is controlled by the FPR, however Bosch pumps have an internal FPR (a simple valve that allows fuel to recuirculate rather than get pumped out). This is set at a certain pressure to activate before the pump self destructs. Therefore the max pressure the pump will supply is governed by itself.
Hence you get a 3 bar pump, 5 bar pump, etc etc. – however even Bosch admit that the internal FPR is usually works way higher than that stated (safety margin for performance of stated output?). Therefore the standard pump, which is a 3 bar pump, will work right up 7.7 bar before the internal FPR activates and you get ‘LOCKOUT’.
However it is rated at 3 bar, so performs best at this output. It’s output for pressure above this drops off quickly, as we see by this:
Set FPR to 3bar, pump delivers 2.25ltr/min, and draws 5amps
Set FPR to 4bar, pump delivers 2.0ltr/min, and draws 6amps
Set FPR to 5bar, pump delivers 1.75ltr/min, and draws 6.5amps
Set FPR to 7.7bar, pump delivers sweet FA – you have reached LOCKOUT.
Ideally you need to know and check:
What fuel pressure you need to supply at (including any preesure increase if FPR is connected to vacum),
What volume of fuel you need supplied at that pressure,
Check the pump will get a constant 12v (or whatever the pump is rated at for the required output),
Check the wiring will be able to handle the amps that is being drawn by the pump at the required output.
Here endith the lesson.