Porsche had been racing a turbocharged 917 in the Can-Am series for around a year when it decided that its 911 needed to go turbo. In 1973, the company presented a concept for a turbocharged 911 road car, and later that year, got to work on a race car companion. The result, , was campaigned by the factory for the 1974 season, and set the stage for dominating race cars to come.
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In appearance, this Carrera RSR looks like a regular 911 with huge fender flares but it's actually quite different in reality. The suspension—with its boxed aluminum trailing arms, and titanium coil springs—is as much 917 as any Porsche street car, and the bodywork is mainly fiberglass.
The engine is a bit of a masterpiece too. For Group 5 racing, the FIA limited engine displacement to 3.0 liters, hence why Porsche went with a relatively small 2.1-liter capacity for this twin-plug flat-six. Like the 911 road car, the crankcase is magnesium, while its valves are titanium and Bosch mechanical fuel-injection is used. Thanks to the giant KKK turbocharger hanging off the back of the car, output was over 500 hp back in the day.
To provide downforce and airflow for the engine's giant intercooler, Porsche fitted the Carrera RSR Turbo with a huge rear wing. Interestingly, the factory painted it black, so it didn't look too big. This was an attempt to make the RSR look at least somewhat like its road-car counterpart, though we're not sure it works.
Porsche only built four turbo RSRs before switching its focus to the 935 for 1976. Of the four, two are in private collections, and one remains in the Porsche museum. This one, R13, will be at its Amelia Island auction next month and it represents the very rare chance to own a factory RSR turbo.
Any RSR turbo for sale would be a big deal, but this one is especially important. It's arguably the most famous of the four built, placing second overall at Le Mans in 1974. It also took home second at the Watkins Glen Six Hours that year, and was subsequently sold to legendary Porsche dealer Vasek Polak.
Gooding & Company expects that this car will sell for $6 million to $8 million. Buy it, and plan on heading to Rennsport Reunion later this year.