Kenichi Yamamoto, who led the engineering team that produced a commercially viable rotary engine at the company now known as Mazda Motor Company and later became its president and chairman, died on Dec. 20 in Kanagawa Prefecture, near Tokyo. He was 95.

His death was confirmed by Mazda, which was called Toyo Kogyo until 1984.

Mr. Yamamoto, a slim and intense mechanical engineer, began his career working in a Toyo Kogyo factory after World War II, but he soon shifted to engine design, which accelerated his rise in management.

Around 1961, Toyo Kogyo’s president asked Mr. Yamamoto to supervise a group of engineers who were trying to perfect the rotary engine that had been invented by a German engineer, Felix Wankel. With few moving parts, the rotary was a compact alternative to conventional engines, with their reciprocating pistons, connecting rods and crankshafts.

The rotary represented opportunity and risk for Toyo Kogyo. Like other small Japanese automobile manufacturers, the company was under pressure from the country’s powerful Ministry of International Trade and Industry to merge with larger companies to increase their overseas competitiveness. If the rotary engine succeeeded, it would allow Toyo Kogyo to maintain its independence.