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 Motor Cars most likely buyer was BMW, which already supplied engines and other components for Rolls-Royce and Bentley cars, but BMW's final offer of £340 million was beaten by Volkswagen's £430 million. A stipulation in the ownership documents of Rolls-Royce dictated that Rolls-Royce plc, the aero-engine maker, would retain certain essential trademarks, including the Rolls-Royce name and logo if the automotive division was sold. Although Vickers plc sold the vehicle designs, nameplates, administrative headquarters, production facilities, Spirit of Ecstasy and Rolls-Royce grille shape trademarks to Volkswagen AG, Rolls-Royce plc chose to license the Rolls-Royce name and logo to BMW AG for £40