Japanese Aero Engines
First a word about Japanese engine names. Any given Japanese engine can have as many as 5-6 different names depending on whether it was an Army or Navy engine, if it was referred to in its experimental form or referred to in its company project code. Late in the war the Japanese tried to sort this out themselves and ended up creating yet another name! This 'unified type designation' is the one seen in the form of (Ha35-21) for Sakae Model 21. "Ha" is short for Hatsudoki which means engine. The "35" refers to a bore/stroke combination that defines the engine type and the "21" refers to the sub model in that bore stroke combo. Whenever you see Sakae 20, the 20 refers to the entire 20 series... in this case it only refers to the model 21 and 22. The Japanese gave engine model numbers to different variants of an engine for various reasons; Reduction gear redesign, supercharger redesign and sometimes very trivial reasons, like a change in the gear ratio for driving the generator. Frankly this complexity goes beyond my understanding so I’ve enlisted some help from Rob at NASM to achieve some basic order and structure in to this section. The aim of this section is not to list every preserved Japanese engine in the world, only to show some of the most well known types and a few locations where they can be viewed.
Type of engine	Country	Place	Status	Additional information
Ha26-II	Singapore	Fort Siloso	PV	Sentosa island
Ha31-21 Zuisei (Mitsubishi)	USA	NASM	S	For their Kawasaki Ki-45Kai “Nick”. Paul Garber storage facility
Ha31-21 Zuisei (Mitsubishi)	USA	NASM	S	For their Kawasaki Ki-45Kai “Nick”. Paul Garber storage facility
Ha32-21 Kasei (Mitsubishi)	USA	NASM	S	Paul Garber storage facility
Ha33-??	Japan	Kawaguchiko Motor Museum	PV	Tokyo
Ha33-62 Kinsei (Mitsubishi)	USA	NASM	S	Paul Garber storage facility
Ha33-62 Kinsei	USA	NASM	S	Paul Garber storage facility
Ha34-11	USA	NASM	S	Tentative identification. Paul Garber storage facility
Ha35-21 Sakae	England	RAFM Cosford	PV
Ha35-?? Sakae	Japan	Kawaguchiko Motor Museum	PV	Tokyo
Ha35-?? Sakae	Japan	Kawaguchiko Motor Museum	PV	Tokyo
Ha35-12 Sakae	Japan	Kawaguchiko Motor Museum	PV	Tokyo
Ha35-?? Sakae	USA	Museum of Flying	PV	Santa Monica, CA
Ha43-11 (Mitsubishi)	USA	NASM	S	Paul Garber Storage facility
Ha43-11 ru (Mitsubishi)	USA	NASM	S	”ru” significes turbocharged engine. Paul Garber Storage facility
Ha45-?? Homare	England	Science Museum	PV	London, possibly model 11, 12 or 21
Ha45-11 Homare	Japan	Kawaguchiko Motor Museum	PV	Tokyo
Ha45-?? Homare	USA	New England Air Museum	PV	Windsor Locks, CT
Aichi Atsuta Model 21 Text on Atsuta engine	Australia	The Cambden Museum of Aviation	PV	Narellan, N.S.W
Atsuta AE1	Australia	Treloar Centre	PV	Australian War Memorial, Canberra
Atsuta AE1	Japan	Kawaguchiko Motor Museum	PV	Tokyo
Atsuta AE1 with radiator	Japan	Kawaguchiko Motor Museum	PV	Tokyo
Atsuta AE1	Japan	Yasukuni Jinja Yushukan	PV	Tokyo
Aichi Atsuta Ha60-32	USA	NASM	PV	Paul Garber Collection, now inside the restored Aichi M6A1
Aichi Atsuta Ha60-31 (AE1P)	USA	NASM	S	Tentative identification. Paul Garber storage facility
Aichi Atsuta Ha60-31 (AE1P)	USA	NASM	PV	Tentative identification. Paul Garber storage facility
Kawasaki Atsuta Ha-40	USA	Weeks Air Museum	PV
Nakajima Mamoru 11 (NK7A)	USA	NASM	S	Tentative identification. Possibly a test example of this engine. Paul Garber storage facility
Nakajima Ha15 “Shi”	USA	NASM	S	Experimental engine not accepted in to Army service. Paul Garber storage facility
Shoda-Hikoki Shoda-Ken No 1	USA	NASM	S	Experimental inverted air cooled V-12, 2 stage supercharger. One of engine. Paul Garber storage facility
Toko Ro.2 (KR10)	USA	Planes of Fame	PV	Chino, CA
Toko Ro.2 (KR10)	Japan	Modern Transportation Museum	PV	Osaka
Ne-20	Japan	Ishikawajima-Harima Heavy Industry Tanashi Factory	RA	The factory museum is not open to the public.
Ne-20	USA	NASM	S	Paul Garber storage facility
Yokosuka Naval Arsenal Engine No3	USA	NASM	S	Experimental W-18 fuel injected, 2 stage supercharger with remote reduction gear. Paul Garber storage facility.