Beginning in the 1960s, Mazda was inspired by the NSU Ro 80, and decided to put a major engineering effort into development of the Wankel rotary engine as a way of differentiating itself from other Japanese auto companies. The company formed a business relationship with German company NSU, and began with the limited-production Cosmo Sport of 1967 and continuing to the present day with the Pro Mazda Championship, Mazda has become the sole manufacturer of Wankel-type engines for the automotive market mainly by way of attrition (NSU and Citroën both gave up on the design during the 1970s, and prototype Corvette efforts by General Motors never made it to production.)