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–Bentley L-series V8 engine the car manufacturing business, and Rolls-Royce plc were not prepared to allow Volkswagen to license this crucial intellectual property. Three way negotiations between Volkswagen Group, BMW and Rolls-Royce plc resulted in BMW purchasing the rights to the Rolls-Royce brand and badge from Rolls-Royce plc for £40m. Rolls-Royce plc, who had been involved in an aero engine joint venture with BMW since 1990 consistently supported their long time business partner during the bidding process for Rolls-Royce and Bentley Motors. German politicians brokered a deal between Volkswagen Group and BMW to ensure BMW would continue to supply engines, transmissions and key components