Rolls Royce Merlin Specifications

Rolls-Royce Merlin with some components labelled.

Merlin II

General characteristics

  • Type: 12-cylinder supercharged liquid-cooled 60° "Vee" piston aircraft engine
  • Bore: 5.4 in (137.2 mm)
  • Stroke: 6 in (152.4 mm)
  • Displacement: 1,648.96 in³ (27.04 L)
  • Length: 69 in (175.3 cm)
  • Width: 29.8in (75.7 cm)
  • Height: 41.2 in (104.6 cm)
  • Dry weight: 1,375 lb (623.7 kg)

Components

  • Valvetrain: Overhead camshaft-actuated, two intake and two exhaust valves per cylinder, sodium-filled exhaust valve stems
  • Supercharger: Centrifugal, 8.588:1 reduction.
  • Fuel system: Twin-choke updraft SU carburetor with automatic mixture control
  • Fuel type: 87 octane rating gasoline
  • Oil system: Dry sump with one pressure pump and two scavenge pumps.
  • Cooling system: 100% ethylene glycol, pressurised.
  • Reduction gear: Spur, 0.477:1

Performance

  • Power output:
    Note: Maximum boost pressures = 87 Octane +6.25lb; 100 Octane fuel +9 lb boost.
    • 880 (656 kW) at 3,000 rpm at take-off.
    • 1,030 hp (768 kW) at 3,000 rpm at 16,000 ft (4,877 m) (+6.25 lb)
    • 1,160 hp (865 kW) at 3,000 rpm at 12,250 ft (3,734 m) (+9 lb) (bmep = 185.7psi)
  • Specific power: 0.70 hp/in (42.9 kW/L)
  • Compression ratio: 6:1
  • Specific fuel consumption: 0.63 lb/(hph) (382 g/(kWh))
  • Power-to-weight ratio: 0.844 hp/lb (1.86 kW/kg)

Merlin 66

General characteristics

  • Type: 12-cylinder supercharged liquid-cooled 60° "Vee" piston aircraft engine
  • Bore: 5.4 in (137.2 mm)
  • Stroke: 6 in (152.4 mm)
  • Displacement: 1,648.96 in³ (27.04 L)
  • Length: 88.7 in (225.3 cm)
  • Width: 30.8 in (78.1 cm)
  • Height: 40 in (101.6 cm)
  • Dry weight: 1,645 lb (746.5 kg)

Components

  • Valvetrain: Overhead camshaft-actuated, two intake and two exhaust valves per cylinder, sodium-cooled exhaust valve stems
  • Supercharger: Two-speed two-stage, boost pressure automatically linked to the throttle, water-air aftercooler installed between the second stage and the engine.
  • Fuel system: Twin-choke updraft carburettor with automatic mixture control
  • Fuel type: 100 Octane from mid 1944 100/150 Grade Aviation fuel
  • Oil system: Dry sump with one pressure pump and two scavenge pumps.
  • Cooling system: 70% water and 30% ethylene glycol coolant mixture, pressurised.

Performance

  • Power output:
    Note: 100 Octane fuel, +12 lb boost.
    • 1,315 hp (981 kW) at 3,000 rpm at take-off.
    • 1,705 hp (1,271 kW) at 3,000 rpm at 5,750 ft (1,753 m) (MS gear)
    • 1,580 hp (1,178 kW) at 3,000 rpm at 16,000 ft (4,877 m) (FS gear)
    Note: 100/150 Grade fuel, +25 lb boost
    • 2,000 hp (1,481 kW) at 5,250 ft (1,600 m) (MS gear) (bmep = 320.2psi)
    • 1,860 hp (1,387 kW) at 11,000 ft (3,353 m) (FS gear)
  • Specific power: 0.95 hp/in (43.3 kW/L)
  • Compression ratio: 6:1
  • Power-to-weight ratio: 0.80 hp/lb (1.76 kW/kg) take-off; 1.21 hp/lb (2.69 kW/kg) 100/150 grade fuel/MS gear.