The diesel principle

In a diesel engine, pure air is drawn into the cylinders and compressed to a very high pressure. This raises the temperature in the cylinders above the ignition temperature of diesel fuel.

When the piston is shortly before top dead centre, diesel fuel is injected into the highly compressed air, which is at approximately +600 °C. The diesel fuel ignites by itself, so spark plugs are not required.

When the engine is cold, compression alone does not reach the ignition temperature. In this case, glow plugs must be used to preheat the engine.

For this purpose, each swirl chamber contains a glow plug which heats the combustion chamber. In addition, the diesel engine has a wax expansion element which, when the engine is cold, moves the injection timing advance piston in the injection pump towards "early" via a Bowden cable. As a result, fuel is injected into the hot air earlier, the cold engine starts more quickly and runs more smoothly. As soon as the engine reaches operating temperature, the wax expansion element resets automatically.