Hiro Type 91

This article is about the engine. For the Hiro Type 91 flying boat, see Hiro H4H.

The Hiro Type 91, (full designation Hiro Type 91 520 hp water-cooled W-12), was a 12-cylinder, water-cooled, W engine developed for aircraft use by the Imperial Japanese Navy in the mid-1930s. Power was in the 450 kW (600 hp) range. Its design was derived from the Hiro Type 90. An enlarged more powerful engine, the Hiro Type 90 600 hp water-cooled W-12 had also been developed, producing 600 hp.

Type 91
Type	W-12 water-cooled piston engine
National origin	Japan
Manufacturer	Hiro Naval Arsenal
Developed from	Hiro Type 90

Applications

• Aichi E10A
• Aichi E11A
• Hiro H4H
• Kawanishi E7K
• Mitsubishi Ka-9

Specifications (Type 91 500hp-1)

General characteristics

• Type: 12-cylinder water-cooled W-block (3 banks of 4 cylinders) aircraft piston engine
• Bore: 135 mm
• Stroke: 160 mm
• Displacement: 27.5 L

Components

• Cooling system: Liquid-cooled

Performance

• Power output:
  
• 620 PS for takeoff
• 520 hp for max continuous

See also

Related lists

• List of aircraft engines

References

• Gunston, Bill (1986). World Encyclopedia of Aero Engines. Wellingborough: Patrick Stephens. p. 74.
• Goodwin, Mike & Starkings, Peter (2017). Japanese Aero-Engines 1910-1945. Sandomierz, Poland: MMPBooks. ISBN 978-83-65281-32-6.