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 Holdings the joint venture company, which also now incorporates Rolls-Royce's existing Bergen engine business, is listed on the Frankfurt Stock Exchange. Following the acquisition of Goodrich by United Technologies Corporation in July 2012, Rolls-Royce announced it would purchase Goodrich's 50% share of Aero Engine Controls to become wholly owned by Rolls-Royce Plc and a part of the Rolls-Royce Group. In May 2014, Rolls-Royce sold its energy gas turbine and compressor business to Siemens for £785 million. In 1990, BMW and Rolls-Royce established the BMW Rolls-Royce joint venture to produce the BR700 range of engines for regional and corporate jets, including the