Abstract: This invention refers to an engine that has the advantage over the internal combustion engines currently in use, that it substantially reduces the emission of contaminants of carbon monoxide, unburned fuel, nitrogen oxides, lead compounds and solid particles, with increased efficiency. This is accomplished by performing the combustion externally to the engine cylinders, in a combustion chamber especially designed to obtain a complete combustion, while maintaining its temperature at a value sufficiently low to reduce the formation of nitrogen oxides by means of an adequate distribution of the combustion air, and by the injection of the water that cools the jackets of the engine into the combustion chamber.