961 – Porsche’s forgotten jewel

The Porsche 961 was a special racing car. Based on the roadgoing technical showcase, the Porsche 959, the Type 961 showed that it had the stamina to go the distance in endurance racing on both sides of the Atlantic. Sadly though, its competition life was restricted to just twelve months, and as such, it is often regarded as Porsche’s forgotten jewel.
Even though the Type 961 race car saw action on the track well before the 959 road car was delivered to its first lucky customer in March 1987, the two models shared the same DNA. While the racing records and history books will show that the 961 did not set the world alight with multiple victories, the racer is held in very high regard by those who both worked on it and those who drove it in competition.

The story of Porsche’s 961 began with the public viewing of the four-wheel drive 959 which was unveiled at the Frankfurt Motor Show in September 1983.
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Initially a production run of 200 Type 959s was envisaged in order to have the car homologated for Group B racing, but when the rules governing that class of circuit racing did not materialise, the cars were prepared for sale to customers for road use, in order to minimise the financial damage to the company. But Porsche wanted to show what the 959 might have been capable of delivering on the track and to this end, one chassis was held back by the factory (#10016) for development into a full race car, the Type 961. This racer was both visually and technically very close to the 959 road car.

The problem with this plan was that there wasn’t a class in which a four-wheel drive car could compete on the international stage, and so the ACO created an invitational category for the 961 to compete at Le Mans. The resultant IMSA GTX class allowed the 961 to compete in the Le Mans 24 Hours as an experimental model, which it did in 1986. This classification also allowed it to compete in the Daytona 3-Hours that same year. With such a limited number of eligible events open to the 961, its career was always going to be a short one, in fact the list of races extended to just three – Le Mans and Daytona in 1986, and again Le Mans in 1987.
And so it was, thirty-five years after the company’s first outing at Le Mans in 1951 with the 356 SL, that Porsche entered the 961 in the 1986 Le Mans 24 Hours. The result in the French endurance classic astounded not only the press and public, but Porsche themselves. But where the 356 SL that developed 40 bhp in 1951 giving it a top speed of around 100 mph, the 961 pushed out 640 bhp and propelled the modern Porsche to a speed of more than 200 mph.

Type 961 development

Developed in the Experimental Department at Weissach, the 961 was a very different car, as it wasn’t a modified road car and nor was it the forerunner of a racing series like the 934 or 935. It was in fact an experimental race car – a one off. All the body panels were formed from either aluminium or composite materials such as fibreglass or lightweight Kevlar panels that were reinforced with steel frames. Even the 911-derived steel roof was replaced by a lightweight panel.

The engineer responsible for the car’s design and testing, Roland Kussmaul, revealed some of the 961’s design origins, “Admittedly it always had a wing similar to the street car. For me this was integrated into the design and it worked well, but the 961 had a bigger wing so that suitable [aerodynamic] balance could be established. The drag coefficient was approximately 0.46.”

The 961’s experimental status was confirmed by the FIA ruling which classified the car for racing in the IMSA GTX class. The FIA still laid down the law in terms of the car’s engine as their ruling stated that the block had to be air-cooled as in the normal 911 production engine. However, the 911 engine is divided into three sections, head, cylinder and crankcase (it had its origins in the 930 Turbo) compared with the head and block in a traditional water-cooled engine. The original French wording from the FIA, however, did not clarify the meaning of the word ‘block’, and so Porsche asked for further clarity on this as Günther Steckkönig explained, “We asked them what do you mean when you say ‘cylinder blocks’ when you have an air-cooled engine like the 911, and so they said after a few days, we had to keep the air-cooled cylinders.”

This presented Porsche with some problems because the 961’s engine had to be based on the production 911 engine, while at the same time producing significantly greater performance. Although the heads could be water-cooled, they could not be in the form of the individual cylinder heads as found in the Group C 962, and so Steckkönig’s race engine department was called on to develop a water-cooled one-piece head for each bank of cylinders.
Chief Engineer of the Racing Engine and Chassis department from 1965, Günther Steckkönig clarifies, “The engineers were told that the 959 engine, or 961 engine, had to be close to or very similar to the Group C engine, but with the big difference, it was to have a one-piece cylinder head.”

The twin overhead camshaft 961 engine was in the meantime being put together by a group of engineers within the 911 production engine department. However, another problem reared its head said Steckkönig, “There were problems with the chain drive and the housing. As you know on the standard 911 engine there is a separate housing for the chain and that had to be sealed on the cylinder head. But the camshaft housing and cylinder block [of the 961] had to be made in one piece and so we helped them by designing the one-piece cylinder head.”
Roland Kussmaul said of his work on the 961, “We used 959 parts used as much as possible, however, the intake system as well as the complete exhaust system were special to the 961.”

The racing 961 literally knocked the socks off the roadgoing 959, which itself developed an impressive 450 bhp from its twin turbocharged 2849 cc engine. With the 961 pushing out a barnstorming 640 bhp, Steckkönig offered the following explanation, “With turbocharging you could do this more easily than if it was a normally aspirated engine. And there was a lot of experience in turbocharging [at Porsche].”

Putting this power on the road was a new high-tech four-wheel drive layout. Known as the clutch-controlled all-wheel drive system, the rear axle in the 959 is driven directly from the gearbox, while the front axle is driven from the rear axle via a controlled clutch. The advantages of the all-wheel drive system included improved straight-line stability when encountering crosswinds, and better acceleration out of corners under slippery road conditions. The ability to convert a hundred percent of the car’s tractive capability greatly improved wheel traction, and although the system did carry with it a weight penalty, the advantages in road holding were thought to outweigh the disadvantages.