Hiro Type 91
# Hiro Type 91

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 Napier Lion. An enlarged more powerful engine, the Hiro Type 90 600 hp water-cooled W-12 had also been developed, producing 600 hp.

## 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
