The engine was designed by
Nakajima Aircraft Company with code name NAM, as a scaled-down and advanced version of the previous NAL design (Army Type 97 850 hp radial engine,
Nakajima Ha5). The
Imperial Japanese Army Air Force called the first of the series the Ha25 (ハ25) and later versions were designated Ha105 and Ha115, in the Hatsudoki designation system and Ha-35 in the unified designation system, while the
Imperial Japanese Navy Air Service designation was Nakajima NK1, with sub-types identified by Model numbers; thus Nakajima NK1 Sakae 10, 20 and 30 series. A total of 21,166 were made by Nakajima; 9,067 were manufactured by other firms. ==Variants==