These models, valued by collectors, are considered by many to be the greatest classic 911s of all-time. RS stands for Rennsport in German, meaning race sport in English. The Carrera name was reintroduced from the 356 Carrera which had itself been named after Porsche's class victories in the Carrera Panamericana races in Mexico in the 1950s. The RS was built so that Porsche could enter racing formulae that demanded that a certain minimum number of production cars were made. Compared with a standard 911S, the Carrera 2.7 RS had a larger engine (2687 cc) developing 210 PS (150 kW; 210 hp) with Bosch (Kugelfischer) MFI, revised and stiffened suspension, a "ducktail" rear spoiler, larger brakes, wider rear wheels and rear fenders. In RS Touring form it weighed 1075 kg (2370 lb), in Sport Lightweight form it was about 100 kg (220 lb) lighter, the saving coming from the thin-gauge steel used for parts of the body shell and also the use of thinner glass. In total, 1580 were made, comfortably exceeding the 500 that had to be made to qualify for the vital FIA Group 4 class. 49 Carrera RS cars were built with 2808 cc engines producing 300 PS (221 kW).
Model year 1974 saw three significant changes. First, the engine size was increased to 2687 cc giving an increase in torque. Second, was the introduction of impact bumpers to conform with low-speed protection requirements of US law, these bumpers being so successfully integrated into the design that they remained unchanged for 15 years. Thirdly, the use of K-Jetronic CIS Bosch fuel injection in two of the three models in the line up— the 911 and 911S models, retaining the narrow rear arches of the old 2.4, now had a 2.7-liter engine producing 150 PS (110 kW; 150 hp) and 175 PS (129 kW; 173 hp), respectively.
