Wolseley Viper

Viper
Rear view of preserved Wolseley Viper
Type	Piston inline aero-engine
Manufacturer	Wolseley Motors
First run	1918
Major applications	Royal Aircraft Factory S.E.5

The Wolseley Viper is a British-built, high-compression derivative of the Hispano Suiza HS-8 liquid-cooled V8 engine, built under licence by Wolseley Motors during World War I.

It powered later models of the S.E.5a, SPAD VII and other British or British-built aircraft designed for the Hispano-Suiza.

• Wolseley W.4A Python I (1917)
  150 hp (110 kW) – licence produced version of the Hispano-Suiza 8Aa with minor structural changes and the weight increased to 455 lb (206 kg), retained the original's low compression 1.8 in (45 mm) pistons and compression ratio of 4.7:1. Only 100 built.¹²
• Wolseley W.4A Python II
  180 hp (130 kW) – high compression version of the Python I with high compression 2 in (50 mm) pistons and compression ratio increased to 5.3:1.²
• Wolseley W.4A* Viper (1918)
  200 hp (150 kW) – broadly the equivalent of the Hispano-Suiza 8Ab, compression ratio of 5.3:1 (19 early production engines had a higher compression ratio of 5.6:1), with 200 hp English Hispano propeller hubs.³
• Wolseley W.4B Adder I (1918)
  200 hp (150 kW) – modified version of the Hispano-Suiza 8B.³⁴
• Wolseley W.4B* Adder II
  200 hp (150 kW) – modified and improved version of the Adder I.³
• Wolseley W.4B* Adder III
  200 hp (150 kW) – modified and improved version of the Adder II with balanced crankshaft.³

• Airco DH.9
• Avro 552
• Bristol M.R.1
• Bristol Tourer
• Cierva C.8
• Martinsyde F.6
• Royal Aircraft Factory S.E.5a
• Sopwith Antelope
• Sopwith Cuckoo

A Wolseley Viper powered Royal Aircraft Factory S.E.5a is owned by, and on display at The Shuttleworth Collection, Old Warden Aerodrome in the UK.⁵

• A preserved Wolseley Viper is on public display at the Science Museum, London.
• A preserved Wolseley Viper is on public display at the Museo Nacional de Aeronáutica de Argentina

Data from Gunston¹ and Lumsden³

General characteristics

• Type: Upright, 90 degree V8
• Bore: 4.72 in (120 mm)
• Stroke: 5.12 in (130 mm)
• Displacement: 716.8 cu in (11.7 L)
• Length: 46.2 in (1,170 mm)
• Width: 33.5 in (850 mm)
• Height: 35.4 in (900 mm)
• Dry weight: 455 lb (206 kg)

Components

• Fuel system: Twin Zenith-Duplex carburettors
• Cooling system: Liquid-cooled
• Reduction gear: Direct drive, Right-hand tractor

Performance

• Power output: 200–210 hp (150–160 kW)
• Compression ratio: 5.3:1