The systems use an individual injection pump mounted on the engine block for each cylinder so it is primarily designed for OHV or "cam in the block" engines.[3] The fuel pumps can be either driven by an extra camshaft lobe or by an electrical supply where each pump unit is connected to the injector via a short precise length high-pressure fuel line as opposed to unit Injector systems which combines both a pump and an injector element in a compact unit.
Both systems feature electronically controlled fuel solenoids for precise timing and the injection of fuel quantity is variably adjusted for each cylinder.