Porsche’s Weapon from the 70s, The Legendary 934: Part 1

By Marcel Hundscheid / Speed-O-Graphica

Over the next couple of weeks, we’re going to take a look back at Porsche’s weapon from the 1970s – the legendary 934.

In the early ’70s, Porsche planned a lightweight racing car for Group 4, powered by a turbocharged version of the 3.0-litre flat six used in the 911 Carrera RS 3.0. From 1976 to 1977, they produced the legendary 911 Turbo RSR 3.0, a race car based on the 930. Using the 930 Turbo as the base, the built the 934 for racing under Group 4 GT rules. This car was internally known as the 934 and was offered to private racing teams for racing under Group 4 FIA regulations.

Instead of the 935 and 936 that was exclusively raced by works teams, the 934 was entered by private teams in the World Sportscar Championship, Division 1 of the German DRM championship and the North American IMSA championship.

Although the 934 participated from 1976 to 1982 in the 24 hours of Le Mans, the more powerful 935 made it almost impossible for the 934 to fight for overall victory in the 24 hour race. As the FIA changed the minimum vehicle weight for Group 4 cars from 1976 in an attempt to reduce their chances of victory, Porsche decided to stop further development and focused on the 930.

In order to meet the homologation requirement for Group 4 GT cars Porsche had to manufacture at least 400 cars. Around 30 cars of the Turbo RSR were produced in 1976. Porsche aimed at the owners of the 911 Carrera RSR 3.0, who were offered a more powerful turbo version with the introduction of the 934.

Group 4 regulations limited changes to the body of the 934 compared to the 930. The 934 could be easily recognised by the 50 mm plastic extensions on the front and rear fenders. For the two water-air heat exchangers of the charge air cooling-system. air inlets on the left and right were mounted on the high front apron reaching to the lower edge of the bumper. The use of light plastic window panes were not allowed under Group 4 regulations. This meant that the 934 received the glass panes of the production model.

To keep the weight of the 934 as low as possible the interior was largely empty. Besides the racing bucket seat, the passenger set, rear emergency seats as well as the floor panels were omitted. The dashboard was only equipped with the standard instruments and additional gauges for turbo boost and fuel system. Remarkably, the brake system contained parts of the Porsche 917, introducing stronger hubs and BBS centre-lock wheels. The Porsche 934 used internally ventilated and perforated metallic brake discs, cooled by an air hose that was laid on the left and right from an opening in the front spoiler.

Porsche used the 3.0-litre flat six from the 930 and fitted it with new pistons and a large KKK turbocharger. Engineers developed this engine further from the 911 Carrera RSR Turbo 2.1, introducing a Bosch K-Jetronic fuel injection system. Initially, the engine developed a maximum 485 hp at 7000 rpm, almost twice as much as the engine of the Porsche 930. Combined with a four-speed gearbox, the 934 reached a top speed of 303 km/h in the longest gear ratio.

Ten 934s were delivered in 1977 to the USA with increased engine output of 540 hp at 7000 rpm. In 1979, further increased engine output gave the 934 a stunning 600 hp at 7200 rpm although the displacement remained unchanged at 2993 cc. This gave the 934 a maximum speed of 305 km/h.

Thirty 934s were issued by Porsche in 1976 (chassis numbers 930 670 0151 to 180), followed by a factory manufactured car (930 670 0540) and 006 0022 as a customer-built-up car. As the 934 was quite popular in the United States Porsche, built ten more cars in 1977 (chassis numbers 930 670 0951 to -0960) identified as 934 ½,  which gives a total of 42 manufactured cars.

The 934 ½ was made for the American IMSA championship only and featured wider wheels and wider fender flares. Porsche used the rear wing from the 935 and opted for a Bosch mechanical injection instead of the Bosch K-Jetronic system.

Group 4 Porsche 934s used in the world sports car championship scored many victories.  In the German Racing Championship (DRM) 934s were entered in Division 1 where the 934 was without a doubt superior to other cars like the Porsche 911 RSR 3.0 and Ford Capri RS 3100. 934s won nine of the ten races. Therefore it was more than remarkable that a Division 2 Ford Escort RS driven by Hans Heyer grabbed the overall title.

In the second part of our Porsche 934 retrospective we will focus on the 934/5.