The hydrogen rotary engine inherits all the advantages of Mazda's gasoline rotary engine. It achieves true Zoom-Zoom performance as well as clean running. Since few modifications are required to adapt the engine to hydrogen fuel, it can be adopted without significant extra cost. In addition, a duel-fuel system that allows the engine to run on either hydrogen or gasoline makes this engine highly practical. The hydrogen rotary engine is a visionary power unit, leading towards a hydrogen-based eco-friendly society.