The 924 began as a Porsche design and engineering project that Weissach undertook for the Vertriebsgesellschaft (VG)- a joint sales and marketing company funded by both Porsche and Volkswagen. VW had made the decision to change its product direction, abandoning the air-cooled rear-engine design that had endured since the beginnings of the company to make way for front-engined vehicles with water cooling. Going back to the 1940s, Porsche had been doing the bulk of the development for Volkswagen as VW lacked the internal research and design divisions to develop sports cars. Volkswagen was on a path to end its reliance on Porsche, but before gave them one last contract and two years to develop a new two-seat sports car to replace the 914. The project was code-named EA425, and was originally intended to be the flagship sports car for Volkswagen and the entry-level sports car for Porsche.
After extensive deliberation among management at VW, the project was scrapped entirely and Porsche struck up a deal to buy the design back. In 1976 the 924 began to roll off of the production lines and quickly became one of Porsche’s best selling models despite criticism for its performance. Naturally, a higher-performing model was in the works and the 924 Turbo with 170 horsepower was released for the 1979 model year.
When it came time for Porsche to plan its racing program for the 1981 season, it was faced with an unusual dilemma. The 936 was outdated and deemed obsolete, and the 911 based 935 was still being raced extensively by privateers, especially in IMSA. The 924 presented a new challenge to the race team who was already itching for a new project: Porsche’s first front-engined, water-cooled race car ready to compete in Group 4. The FIA mandated that 500 examples were required for homologation, although by the time the 924 Carrera GT was in development the requirements had been relaxed to 400.
Four racing versions went to Le Mans in June 1980 as 2-liter 924s and designated as the Carrera GTP. Overall weight was reduced further over 500 lbs to just 2,046 lbs, and power was increased substantially to 320 hp. Three of the four finished the race and the best finish of the group was by Jurgen Barth and Manfred Schurti, who worked their way up through the field from qualifying 46th of 50 cars to a 6th place overall finish. They were bested by only four purpose-built prototypes and one 700 hp 935, making the finish all the more impressive.
The Carrera GTS, was produced as an evolution model of the 924 Carrera GT within Group 4 regulations and intended strictly for competition. The FIA only required 50 new examples, and according to historian and racer Jurgen Barth, Porsche stopped production at 59 GTS examples with a price tag of $55,900 in 1981- nearly double the price of the earlier 924 Carrera GTs.
Like the 924 Carrera GT, the GTS was lowered 15mm and its track widened by 59mm at the front and 79mm in the rear. 7 and 8 inch wide forged aluminum Fuchs were fitted, wider plastic fenders with dramatically flared arches and a new front spoiler give it a menacing appearance over the stock 924 Turbo. The GTS can easily be identified by the Perspex covers in place of the pop-up units, the plastic molded GTS badge at the rear, and an even more aggressive front spoiler, Aluminum was used for the hood and doors, reducing the overall weight of the GTS by 128 lbs. Boost pressure was increased from 11 psi to 14.5 psi, raising horsepower to 245hp at 6,250 rpms and 247 ft-lb of torque at 3,000 rpms. 0-60 times were quoted at six-seconds flat and a top speed of 155 mph, making it significantly faster than the 911 SC of the era.
The ultimate evolution of the 924 was the 924 GTS Clubsport. This car is one of just 15 of the 59 924 GTSs to feature the Clubsport package. The package further reduced weight with plastic door windows with sliding panels, thinner and lighter front windshield and a molded clear Plexiglas rear hatch. The fiberglass hood features a functional air intake and racing hold-down pins instead of conventional latches. The suspension was upgraded from torsion bars and steel shocks to Bilstein coil-overs at all four corners, the stock steel rear semi-trailing arms replaced with cast light-alloy, and the ventilated and cross-drilled disc brakes came from the 930 Turbo parts bin. The uprated GTR five-speed transaxle with a 40 percent limited-slip was cooled with an additional radiator. Inside, the interior features a Matter-fabricated alloy roll cage, 935 racing seats with full harnesses and a suede-wrapped steering wheel.
Most importantly, the Clubsport option added even more power to take advantage of the trimmed weight. The bore was increased slightly to 2,093 cc and a larger intercooler helped to produce 280 horsepower. It was capable of 0-60 in 5.2 seconds and reached a top speed of 160mph. At the time, it was rumored to be the fastest production car Porsche had ever built.