These models, valued by collectors, are considered by many to be the greatest classic 911s 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 (207 hp/154 kW) with 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 bodyshell 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).
In 1974, Porsche created the Carrera RS 3.0 with K-Jetronic Bosch fuel injection producing 230 PS (169 kW). It was almost twice as expensive as the 2.7 RS but offered a fair amount of racing capability for that price. The chassis was largely similar to that of the 1973 Carrera RSR and the brake system was from the Porsche 917. The use of thin metal plate panels and a spartan interior enabled the shipping weight to be reduced to around 900 kg (1984 lb).
The Carrera RSR 3.0 was sold to racing teams, and scored outright wins in several major sports car races of the mid 1970s. Also, a prototype Carrera RSR Turbo (with 2.1 L engine due to a 1.4x equivalency formula) came second at the 24 Hours of Le Mans in 1974 and won several major races, a significant event in that its engine would form the basis of many future Porsche attempts in sportscar racing. Save for the earlier Porsche 917, it can be regarded as Porsche's start of its commitment to turbocharging also in road cars.