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G.W. Dale Ltd
139 Newcastle Street
Burslem
Stoke on Trent
Staffordshire
ST6 3QJ

Phone: +44 (0) 1782 837 665
Fax: +44 (0) 1782 839 550

The Diesel Engine


Rudolf Diesel developed the idea for the diesel engine and obtained the German patent for it in 1892. His goal was to create an engine with high efficiency . Petrol engines had been invented in 1876 and, especially at that time, were not very efficient.

The main differences between the petrol engine and the diesel engine are:

  • A petrol engine intakes a mixture of gas and air, compresses it and ignites the mixture with a spark. A diesel engine takes in just air, compresses it and then injects fuel into the compressed air. The heat of the compressed air lights the fuel spontaneously.

  • A petrol engine compresses at a ratio of 8:1 to 12:1, while a diesel engine compresses at a ratio of 14:1 to as high as 25:1. The higher compression ratio of the diesel engine leads to better efficiency.

  • Petrol engines generally use either carburetion , in which the air and fuel is mixed long before the air enters the cylinder, or port fuel injection , in which the fuel is injected just prior to the intake stroke (outside the cylinder). Diesel engines use direct fuel injection -- the diesel fuel is injected directly into the cylinder.


©Image courtesy Baris Mengutay

Note that the diesel engine has no spark plug, that it intakes air and compresses it, and that it then injects the fuel directly into the combustion chamber (direct injection). It is the heat of the compressed air that lights the fuel in a diesel engine.