Using the 930 Turbo as a basis, Porsche built the 934 for Group 4 GT racing. It replaced the outgoing Carrera RSR while winning GT Championships in Europe and performing very well in America for Trans Am.

Porsche built the 934 from a standard 930 bodyshell and production rear spoiler, but almost nothing else was left alone.

The suspension was converted to solid mounts and nylon bushings with adjustable anti-roll bars. New brakes from the 917 were fitted along with stronger hubs and BBS center-lock wheels which at 16 inches, were larger than the outgoing the RSR and required more drastic wheel arches.

Inside the was stripped and included an aluminum roll-cage as well as new gauges for fuel and turbo boost levels.

A 120 liter fuel tank filled the front trunk along with a oil tank and battery. The oil tank fed a front mounted oil cooler which was fed from a huge cut-out in the spoiler. Beside these were ducts that led to the rear intercoolers. This system added nearly 45 lbs to the car, but was necessary since an air-to-air intercooler could not fit under the standard engine hood which was mandated by the regulations.

Porsche took the standard 930/75 engine and fitted new pistons while the block, crankshaft and connecting rods were all production parts. Furthermore the standard ignition and mechanical injection system had to be used. With a large KKK turbocharger, around 485 bhp was possible at 1.4 bar of boost.

The first 934 prototype appeared in September of 1975 and it was instantly faster than the outgoing Group 5 Carrera RSR 3.0. This meant almost every team upgraded to the 934 including Kremer and Gelo. As a result the car was very sucessful in the European GT Championship which was won by Toine Hezemans in the Gelo car. The same could be said about the German GT Championship which effectively became a Porsche-only affair.

Later in production Porsche released a 934½ specification which included a larger rear wing and updated 930/73 engine which could produce 600 bhp. These were primarily raced in Group 5 and many were used in America for Trans Am duty under the Vasek Polak banner. They dominated the 1976 season with George Folmer behind the wheel and in 1977 Peter Gregg won the championship. By 1977 the 934 was finally accepted by IMSA and many of those cars were updated to Group 5 spec.

At Le Mans, the 934 was a regular fixture and competed against the Ferrari 512 BB LM. They took class honors in 1977, 1979 and 1981.

Racer Nick Faure recalls getting insights from Ickx: “The single-turbo cars, whether 934 or 935, were a handful with all that turbo lag. Jackie Ickx told me to commit the car to the corner and saw away at the steering wheel to scrub off the speed whilst not lifting your right foot.”