The radial piston pump should inject a specific amount of fuel, at a specified time, under high pressure, through the injectors, into the combustion chamber.
The most important component in the high pressure development is the central pump element. It consists of a cylinder which is rotating at the same RPMs as the pump, in which two - or more - small radial pistons (yellow) are moved inwards for a short time, against the cetrifugal forces, by a cam ring through roller tappets. Holes between the rotary cylinder and the casing provide for the supply and the correct distribution of the fuel to the respective cylinders. The volume regulation is controlled in various ways, depending on the manufacturer. Thanks to the principle of radial pistons and cam ring, higher pressures are possible for the modern direct injection. 11/10