In general, engines using the Diesel cycle are usually more efficient, than engines using the Otto cycle. The diesel engine has the highest thermal efficiency of any practical combustion engine. Low-speed diesel engines (as used in ships) can have a thermal efficiency that exceeds 50%. The largest diesel engine in the world peaks at 51.7%.
How gas and diesel engines work. At their core, gasoline- and diesel-powered engines work under the same principles. Both convert chemical energy from fuel into mechanical energy to produce movement.
This discussion of engines is limited to power plants involving the combustion of a fuel inside a chamber that results in the expansion of the air/fuel mixture to produce mechanical work. These internal combustion engines are of two types: gasoline spark-ignition and diesel compression-ignition.
In theoretical terms they are the same. Horsepower is a measure of power and is equal to 550 foot pounds per second or about 700 watts. Typically engine companies rate their engines by peak horsepower, which may not be at a speed the engine typically runs at. What really does the work is torque, reason being the force generated in a rotating Furthermore, a diesel engine does not require spark plugs. When a gasoline engine compresses its fuel/air mixture, it does so at a ratio ranging from roughly 8:1 to 12:1, with some racing engines .