Compression and the fuel system are the most important factors for the efficient operation of the diesel engine. The preheating system heats the compression air necessary for cold engine starting.
The diesel engine compresses the air to attain the heat necessary for the fuel to self-ignite. Therefore, compression in the diesel engine performs the same role as ignition in the gasoline engine. Also as with the gasoline engine, a great explosive pressure can be attained by compressing the air.
2. Fuel system
The diesel engine does not have a throttle valve for controlling engine output like the gasoline engine. The output of the gasoline engine is controlled by opening and closing the throttle valve, thereby controlling the amount of air-fuel mixture taken in. However, the diesel engine controls engine output by adjusting the fuel injection volume. Furthermore, as combustion starts with fuel injection, it also adjusts fuel injection timing. This corresponds to the ignition timing of the gasoline engine.
For various purposes, some engines are equipped with an intake shutter for decreasing noise, engine stopping, or decreasing engine vibrations while engine stopped.
3. Preheating system
The preheating system is particular to the diesel engine. The preheating system heats the compression air by electrically for cold engine starting. There are two typesThe glow plug type, which heats the air inside the combustion chamber, and the intake heater type, which directly heats the air coming from the air cleaner.