title: Rolls-Royce Pennine
text: # Rolls-Royce Pennine
  
  The Rolls-Royce Pennine was a British 46-litre air-cooled sleeve valve engine with 24 cylinders arranged in an X formation. It was an enlarged version of the 22-litre Exe; a prototype engine was built and tested, but never flew. The project was terminated in 1945, being superseded by the jet engine.
  
  A 100-litre 5,000 hp X32 (twin-X16) version of the Exe/Pennine, originally known as the Exe 100, was to have become the Rolls-Royce Snowdon.
  
  Rolls-Royce air-cooled engines, intended for commercial transport aeroplane use, were named after British mountains, e.g. The Pennines and Snowdon.
  
  ## Specifications (Pennine)
  
  ### General characteristics
  
  * Type: 24-cylinder supercharged air-cooled 90 degree X layout aircraft piston engine
  * Bore: 5.4 in (137.1 mm)
  * Stroke: 5.0 in (127 mm)
  * Displacement: 2791 in³ (45.73 L)
  * Length: 106 in (2692 mm)
  * Width: 39 in (991 mm)
  * Height: 37.5 in (952 mm)
  * Dry weight: 2,850 lb (1,293 kg)
  
  ### Components
  
  * Valvetrain: Sleeve valve
  * Supercharger: Gear-driven centrifugal type supercharger, single stage, two speed
  * Fuel type: Petrol
  * Cooling system: Pressure air-cooled
  
  ### Performance
  
  * Power output: 2,740 hp (2,043 kW) at 3,500 rpm, +12 psi boost at sea level
  * Power-to-weight ratio: 0.96 hp/lb (1.58 kW/kg)
  