You can say that the function of an Otto engine and a Diesel engine are very similar. Four strokes are required just like in the Otto engine. At least one inlet valve and one outlet valve are also required for each cylinder. The crankshaft rotates two revolutions to complete a work cycle, and the camshaft one revolution. but because the fuel is different from petrol, a spark plug is not required. The diesel is ignited by the high heat in the cylinder. The high heat is achieved by the fact that a Diesel engine has significantly higher compression than an Otto engine. The compression is approximately 20-30 bar.