contd...

injector nozzle and the fuel is injected. Opening of the solenoid valve releases the fuel pressure and the injection ends. Another design of EUI developed by Cummins Engine Company, Inc. consists of two plungers in the same unit injector, one controls injection timing and the other controls the injection quantity. As the dead volume between the pumping plunger and injector nozzle is very small, very high injection pressures can be used with a high reliability and injection efficiency. Operation of the EUI at more than 2500 bars has been demonstrated.

The EUI can be used to provide pilot injection. A constant fuel temperature at each injector must be kept so that each injector delivers the same mass of fuel to each engine cylinder. A number of sensors provide input data on the engine speed, load, camshaft position, inlet manifold air temperature and pressure, coolant temperature etc., to the electronic control unit (ECU) for control of fuel injection quantity and injection timing. For small high-speed diesel engines, EUI is not employed due to its large size and high cost. Instead, electronic distributor pumps are used. Now,  the common rail injection systems are finding wider application in the small size, high speed multicylinder  diesel engines.