Injection nozzles for diesel engines inject the fuel into the combustion chamber, atomize it and seal the combustion chamber by means of the nozzle needle. In the Common Rail System, the injection nozzle is part of the injector.

The injection nozzle consists of the nozzle body the cone of which protrudes into the combustion chamber. The injection orifices through which the fuel is injected are bored in the nozzle cone. The number, configuration, length and diameter of these injection orifices permit the shape of the injection spray to be formed in a way that is ideally matched to the engine cylinder.

Inside the nozzle body is the nozzle needle which, when closed, blocks the injection orifices. For fuel injection, the nozzle needle is raised by the hydraulic servo system of the injector so that the injection orifices are opened. The faster the nozzle needle can be opened and re-closed, the more precisely the injection rate can be controlled.

The injection rate and the shape of the injection spray have a decisive influence on fuel consumption and raw emissions from the engine.