Hi! According to Gakken's The IJA aircraft, Nakajima Ki-82 was a twin engine 4 crew high speed heavy bomber called heavy bomber Otsu(乙)planned in 1940. Ki-82 project had following two plans.
(1) Noaral design with Nakajima Ha-45 engine(take off power 1,800hp). Maximum speed was 580km/h.
(2) Radical design with Nakajima inverse W18 liquid cooling Ha-39 engine(take off power 2,100hp/2600rpm, single stage two speed mechanical supercharged) and skin cooler. Maximum speed was 650~670km/h.(if use normal radiator, maximum speed was 610~620km/h)
Nakajima Ki-82 was abandoned because Mitsubishi Ki-67(called heavy bomber Kou(甲)) with Ha-214(Ha-42, take off power : 2,500hp) engine had high maximum speed(630~640km/h) possibility. Ki-82 full scale mockup was made.(Ha-45 engine version?)
Nakajima Ha-39(Nakajima domestic name : NLH-11) engine's base were Nakajima NWA and NWE(Ha-15,take off power : 2,000hp), normal W18 51.2L engine)
Ha-39 specification
Displacement : 51.2L, Bore : 146mm, Stroke : 170mm, Compression ratio : 7, 1960hp/2000m/2500rpm, 1780hp/5500m/2500rpm
Nakajima Ha-39 engine development terminated at the beginning of Pacific war,Nakajima concentrated Homare engine development.
