In a diesel engine, what initiates and controls the combustion?

In a diesel engine, the timing of fuel injection is crucial because it determines when and how the fuel is introduced into the combustion chamber relative to the piston’s position and the intake of air. Unlike gasoline engines that rely on spark plugs to ignite the air-fuel mixture, diesel engines operate on the principle of compression ignition; the air is compressed to a high temperature and pressure which ignites the fuel once it is injected.

By controlling the timing of the fuel injection, the engine can optimize combustion for efficiency and power output. If injection occurs too late, the combustion process will not be as effective, causing power loss and potentially increasing emissions. If it happens too early, it can result in knocking or engine damage. Hence, the precise timing of fuel injection directly influences the combustion process and engine performance in diesel engines.