Legends at the Porsche Museum: 911 RSR 2.1 Turbo

By Marcel Hundscheid / Speed-O-Graphica

During our visit to the Porsche Museum in 2020, we came eye-to-eye with another 911 that wrote history – the 911 RSR 2.1 Turbo, Porsche’s first racing 911 equipped with a turbo. In 1974 Porsche competed with this car in the Group 5 category of the FIA’s World Championship for Makes. Let’s take a look around.

FIA Group 5 at the time was a silhouette class, in which racing cars appeared with the goal of stimulating the sale of road cars. Therefore, the intention for Porsche was to make the RSR Turbo look like a 911, and the huge rear spoiler was painted black to make it less noticeable. This car was created to help the development of Porsche’s new 911 Turbo ahead of its launch for the 1975 model.

The marque had already pioneered turbocharged race engines in 1972 and 1973 with the Porsche 917, however the FIA had decided that engine capacity should not exceed 3.0 litres. To comply with Group 5 regulations, Porsche developed a 2.14-litre engine equipped with a magnesium crankcase, polished titanium rods, enlarged oil pumps, dual ignition, mechanical injection and sodium cooled valves.

An additional challenge, was that a car intended for the prototype class had to be equipped with an atmospheric power source of up to 3 litres. Using the equivalence factor of 1.4, the final engine to be used could not exceed 2143 cc. However, the street version of the 911 Turbo would have a 3.0-litre engine. Porsche mounted a mighty KKK ’33’-turbocharger that generated between 450 and 500 hp at 7600 rpm using a 1.4 bar boost. Porsche has achieved that displacement by reducing the bore and stroke of the naturally aspirated 3.0-litre RSR engine.

As Porsche would run the 911 RSR 2.1 Turbo in the prototype class, it faced relatively few restrictions regarding aerodynamics. Porsche only built four RSR 2.1 Turbos, all of which have a chassis number with an R. Three of the four were used for racing, while the fourth was a development car.

Porsche immediately scored a second place in the general classification during its debut at the 24 Hours of Le Mans in 1974 with Gijs van Lennep and Herbert Müller. Despite their reputation at that time, this was a phenomenal achievement, as it was the first turbocharged car ever to start at Le Mans. The achievement took on even more significance when the 911 RSR 2.1 Turbo was found to have beaten sports prototypes from Matra, Lola, Gulf Mirage, Chevron, Ligier and the Porsche 908.

By Marcel Hundscheid / Speed-O-Graphica