There are numerous companies working on hydrogen-fueled internal combustion engines, most notably BMW with its Hydrogen7. Mazda however, is uniquely positioned to take advantage of hydrogen as a combustion fuel. They are, after all, the only manufacturer currently building Wankel rotary engines. The nature of the rotary engine - where the intake and combustion chambers are separate - makes the design well suited to the rapid burn characteristics of hydrogen. Mazda is also using direct injection of the hydrogen to time the combustion more precisely. Piston engines can have issues with backfiring when fueled on H2 but Mazda has been running a fleet of over 30 hydrogen-fueled rotary RX-8s for several years with some success. Last week at the Paris Motor Show, James Muir, Mazda Europe's CEO, told AutoCar that the Japanese carmaker plans to mass produce hydrogen-fueled Wankel engines but it will take another half decade. The main stumbling block? Same as for everyone else: hydrogen storage.