Why is a diesel engine also called an self-ignition engine?

A diesel engine is referred to as a self-ignition engine because it relies on the high compression of air within the cylinder to ignite the fuel automatically when it is injected. This process occurs without the need for a spark plug, as found in gasoline engines.

In a diesel engine, when air is compressed, its temperature increases significantly. When the diesel fuel is injected into this highly compressed and hot air, it ignites spontaneously. This characteristic distinguishes diesel engines from other types, such as those that use spark ignition.

Understanding this principle is essential because it impacts vehicle maintenance, fuel choice, and performance. In Germany, specific regulations regarding emissions and vehicle efficiency are closely linked to the type of engine. Therefore, knowing the operational principles of engines helps in adhering to traffic laws and environmental standards.