The Diesel engine runs on the Diesel Cycle. All you have to do is compare the P-V curves of the Otto and Diesel Cycles, and you will see the link. If you extend the 'compression' curve of the Otto cycle past the usual 'ignition point', you'll get exactly the curve of the Diesel Cycle. (Not quite that simple, to be sure.)sid_galt said:But the diesel cycle engine runs on the brayton cycle. I am talking about the Otto cycle which is more efficient since the pressure rises while combustion and further energy can be extracted from the exhaust if it is not fully expanded to atmospheric pressure.