There’s just something about Porsche racing turbos. When Porsche introduced the 917/30 to Can-Am racing, it almost single-handedly shut down the series. Only 3 years later, it introduced the 935 to FIA World Championship Group 5 racing.
Technically speaking, the 935 was an evolution of the Porsche Carrera RSR 2.1 Turbo prototype, which finished second overall at the 1974 24 Hours of Le Mans. But it was a pretty significant evolution. Under Group 5 rules, also known as 'Silhouette rules', several significant modifications were allowed. They included bodywork modifications, larger wings, wider axles and water cooling, as long as the basic silhouette of the car remain unchanged when viewed from the front. The 935's engine was a turbocharged version of the regular 3.0 L flat-6. Initially it produced 560 hp at 7900 rpm and 438lb-ft of torque at 5400 rpm. Boost was between 1.35 and 1.55 bar. Displacement was reduced to 2.85 liters, and with the turbo charging penalty multiplier of 1.4, it fit into the 4.0 L class - which had a minimum weight of only 2,140 pounds. The empty 935 tipped the scales at under 2000 pounds, so they could add the additional 200 as they pleased to improve balance and handling. The large turbocharger in conjunction with mechanical fuel injection caused serious turbo lag, followed by a large fireball spitting from the exhaust. Depending on the series and the rule allowances, the 935 was capable of an enormous amount of power - some claim up to 800 hp. In a more ‘pedestrian’ trim in that first year, at preseason testing at Paul Ricard circuit the 935 showed a top speed of nearly 185 mph.
In the 935’s first official race, the 6 Hours at Mugello, the the Martini Racing sponsored factory entry of Mass and Ickx won, and Porsches occupied the first seven places ahead of a BMW in eighth, which according to the points scheme meant that Porsche had now twenty points, and BMW three - after one race. The factory 935 also scored the pole, fastest lap and win at the 6 hour race at Vallelunga, where a BMW was second.
After the second race, the rule makers insisted that the 'whale tail' of the road-going 930 must fit on the race car. The air-to-air intercooler setup under the rear hood had to be altered to a more compact air-to-water layout, which cost Porsche several weeks of testing.
The hastily modified 935 again won the pole and fastest lap at the Silverstone 6-hour race, but only finished 10th due to a clutch problem at the start. A privately entered BMW 3.5 CSL won the race. Interestingly BMW Motorsport had entered a turbo 3.2 CSL in that race, driven by Ronnie Peterson and Gunnar Nilsson. That new BMW had qualified only one second behind the factory 935, and two seconds ahead of the third placed Kremer 935.
Due to a lack of serious competition in 1976, the Porsche factory decided not to defend its sportscar championship, leaving it to customer cars. But the factory continued to develop and occasionally race a single new 935 in the 1977 World Championship for Makes season, just to ensure they were still competitive against other turbo makes. Customers were not happy that the factory was beating them with a newer car, but since the 935/77 was much less reliable than it’s predecessor, it would be beaten in five of the nine WCM events. The new car body was changed significantly to lower drag, resulting in an added 6 mph higher top speed at Paul Ricard, where it lapped three to four seconds faster than the previous model. The front fenders, which in 1976 had followed the hood, now protruded above the hood line, and also accommodated the mirrors. The rear fenders were also altered, but the biggest change was the addition of a second rear window above the standard one. This allowed cleaner air flow to the rear wing, where the single turbo was replaced by two KKK units. This improved throttle response and power, but suffered several head gasket failures.
The factory 935/77 qualified sixth at the 1977 24 Hours of Le Mans, behind the Renault Alpines and the 936s, but engine troubles ended the race early. As in 1976, a 936 won, with a customer 935 finishing third overall. They’d have some work to do for 1978.
For 1978, they developed the third, and final version of the 935, the 935/78, and it was built for one purpose: Le Mans. At this point in Porsche’s history, they had recently introduced the water-cooled front engine Porsche 928 and Porsche 924models. Still reeling from the head gasket failures of the 1977 model, Porsche introduced water-cooled cylinder heads in the 1978 engine, and also equipped them with four valves per cylinder. Displacement was enlarged to 3.2 L, increasing output to a conservatively rated 750 hp. They even went to such lengths to move the driver seat to the right side, since Le Mans was run clockwise, for better weight distribution and sight in right-hand corners - a very distinctive feature of the 1978 model.
The new car took full advantage of a new loophole in the Group 5 rules - one introduced for BMW that allowed the floor to be cut to accommodate the exhaust pipes from the engine. As this rule applied for the rear engine Porsche, this allowed them to cut away the whole floor pan of the 911, and drop the body nearly 4 inches. The gearbox was mounted upside down to reduce the angle of the drive shafts. The rules did not limit the forward extension of the rear aerodynamic devices, so Porsche even added fairings to the doors, bridging the gap between the front and rear fenders. They were later shortened, covering only the front third of the doors. Because of its white color and long tail, built for low drag, the 935/78 is often referred to as Moby-Dick.
With this version, Mass and Ickx won the 6 hour race at the fast Silverstone Circuit, as well as taking pole and fastest lap, being only 4 seconds slower than the times of James Hunt in the 1977 British Grand Prix, which covered only a quarter of the distance.
At the 1978 24 Hours of Le Mans, the 935 qualified third, barely beaten by a Renault Alpine and a 936. The lap times were a substantial 15 seconds quicker compared to 1976. With its 3.2L engine, it was the fastest car on the straight in Le Mans at speeds aproaching 235 mph, easily passing the prototypes. The engine had to be replaced just before the race, though, and with added problems early in the race, Moby Dick was not a legitimate contender, finishing 8th behind three customer 935.
Awaiting significant rule changes coming for 1982, Porsche did not enter as a factory in 1979 or 1980, and granted only limited support to customer efforts. Factory racing was mainly in the form of the Porsche 924 turbo variants called the Carrera GT, with some success.
By 1984 the 935 had won over 150 races worldwide, including more than 20 class wins. It scored outright wins in the 1979 24 Hours of Le Mans, and won the 24 Hours of Daytona and the 12 Hours of Sebring six times each. It was also undefeated in the German DRM between 1977 and 1979, posted victories in the IMSA GTX class, and won three 1000km races at the Nürburgring. The 935 also took Porsche to victory in the FIA World Championship for Makes each year from 1976 to 1979.