Editing Diesel engine (section)

=== Overview ===
The characteristics of a diesel engine are<ref name="Pischinger_2016_348" />
* Use of [[compression ignition]], instead of an ignition apparatus such as a [[Spark-ignition engine|spark plug]].
* Internal mixture formation. In diesel engines, the mixture of air and fuel is only formed inside the combustion chamber.
* Quality torque control. The amount of torque a diesel engine produces is not controlled by throttling the intake air (unlike a traditional spark-ignition petrol engine, where the airflow is reduced in order to regulate the torque output), instead, the volume of air entering the engine is maximised at all times, and the torque output is regulated solely by controlling the amount of injected fuel.
* High [[Air–fuel ratio#Air–fuel equivalence ratio (λ)|air-fuel ratio]]. Diesel engines run at global air-fuel ratios significantly leaner than the [[Stoichiometry#Stoichiometric ratio|stoichiometric ratio]].
* [[Diffusion flame]]: At combustion, oxygen first has to diffuse into the flame, rather than having oxygen and fuel already mixed before combustion, which would result in a [[premixed flame]].
* [[Heterogeneous]] air-fuel mixture: In diesel engines, there is no even dispersion of fuel and air inside the cylinder. That is because the combustion process begins at the end of the injection phase, before a homogeneous mixture of air and fuel can be formed.
* Preference for the fuel to have a high ignition performance ([[Cetane number]]), rather than a high knocking resistance ([[octane rating]]) that is preferred for petrol engines.