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 Allison is now known as Rolls-Royce Corporation, part of Rolls-Royce North America. In 1999 Rolls-Royce acquired Vickers plc for its marine businesses. The portion retained is now Vinters Engineering Limited. Rolls-Royce sold Vickers Defence Systems (the other major Vickers area of business) to Alvis plc in 2002, which then became Alvis Vickers. Rolls-Royce has established a leading position in the corporate and regional airline sector through the development of the Tay engine, the Allison acquisition and the consolidation of the BMW Rolls-Royce joint venture. In 1999, BMW Rolls-Royce was renamed Rolls-Royce Deutschland and became a 100% owned subsidiary of Rolls-Royce