These types of engine are chosen by manufacturers for various reasons – primarily where a low engine profile is desirable.

Similarly to EUI, each injector is fed fuel by a solenoid-controlled spill valve situated in the body of the EUP. This actuator is controlled by an electronic control unit (ECU) which receives continuous signals from various sensors situated around the engine. The information received is compared with the optimum values stored within the ECU memory. The appropriate signal is then sent to the actuator enabling it to deliver the precise amount of fuel at the exact timing point required by the engine.