Rolls-Royce Merlin exhaust flow and waste-gates, meant that this option was rejected in favour of the two-stage supercharger. Fitted with the two-stage two-speed supercharger, the Merlin 60 series gained 300 horsepower (224 kW) at over the Merlin 45 series, at which altitude a Spitfire IX was nearly faster than a Spitfire V. The two-stage Merlin family was extended in 1943 with the Merlin 66 which had its supercharger geared for increased power ratings at low altitudes, and the Merlin 70 series that were designed to deliver increased power at high altitudes. While the design of the two-stage supercharger forged ahead, Rolls-Royce also
Rolls-Royce Derwent Rolls-Royce Derwent The Rolls-Royce RB.37 Derwent is a 1940s British centrifugal compressor turbojet engine, the second Rolls-Royce jet engine to enter production. Essentially an improved version of the Rolls-Royce Welland, itself a renamed version of Frank Whittle's Power Jets W.2B, Rolls inherited the Derwent design from Rover when they took over their jet engine development in 1943. Performance over the Welland was somewhat increased and reliability dramatically improved, making the Derwent the chosen engine for the Gloster Meteor and many other post-World War II British jet designs. When Rover was selected for production of Whittle's designs in 1941 they set