Purpose and Function
Modern EFI fuel systems circulate as much as 200 litres per hour (~ 3 litres / min ) of fuel at pressures between 2.5 - 3.5 bar ( 250 - 350 kpa ) Modern electric fuel pumps are “Positive Displacement” type pumps, this means that the pump cannot produce pressure unless it is acting upon a restriction. The only restriction in the system should be the fuel pressure reg- ulator. The regulator controls the system pressure; the pressure abilityor flow volume capacity of the fuel pump will not alter the system pressure. Due to the high pressure and volume requirements placed upon these pumps, manufacturing tolerances are extremely fine. Motor speeds can be as high as 10,000 RPM and the clearances within the pumping elements down to microns. Cleanliness of the fuel system is vital, with an efficient high qual- ity filter as an essential part of the fuel system.

Important Note.
• Bosch Fuel Pumps have their flow rates defined in N-Heptane as part of their engineering specification. N-Heptane is a pure chemical and does not have the same viscosity and density as standard petrol. Hence the N-Heptane flow rate figures stated should be used as a general guide for comparison purposes only.
• Bosch Fuel Pumps are designed for use with standard grade petrol. Subject to statutory warranties, Bosch does not warrant the performance characteristics or specifications of these fuel pumps if they are used with Alcohol or Ethanol based fuels or fuel additives that are corrosive.