The RAF 3 was a British liquid-cooled, V-12 engine developed for aircraft use during World War I. Based on the eight–cylinder RAF 1 it was designed by the Royal Aircraft Factory but produced by the two British companies of Armstrong Whitworth and Napier & Son. The RAF 7 was a high compression version of the same engine.
RAF 31914 - Prototype engine, 200
horsepower (150 kW).
RAF 3a1914 - Main production variant, increased
bore, 260 horsepower (194 kW). 29 built by Armstrong Whitworth, 260 built by Napier & Son.
RAF 7300 horsepower (224 kW) high compression version with high-lift
camshafts.
Airco DH.4Royal Aircraft Factory R.E.7Data from Lumsden
Type: 12-cylinder, upright, 60-degree Vee engineBore: 4.5 in (114.3 mm)Stroke: 5.5 in (140 mm)Displacement: 1,049.4 cu in (17.24 L)Dry weight: 780 lb (354 kg)Valvetrain: Overhead valve, both valves operated by a single pushrodCooling system: Liquid-cooledReduction gear: 0.5:1, left-hand tractorPower output: 260 hp (194 kW) at 1,750 rpm (takeoff power)Specific power: 0.25 hp/cu in (11.25 kW/L)Compression ratio: 5.3:1Power-to-weight ratio: 0.33 hp/lb (0.54 kW/kg) 