1981 - 1991 Porsche 959

In the mid-1980s, Porsche created a stunning supercar called 959. Not only rewrote all the world records for top speed and acceleration, the car also featured many advanced technologies, such as computer-controlled 4-wheel drive, 4-valve engine, sequential turbochargers, self-leveling suspensions, carbon-fiber body and advanced aerodynamics. No supercar in before had ever got so much technology breakthrough as the 959, nor any subsequent supercar did that.

Philosophy And Development

Unlike Ferrari and Lamborghini, Porsche did not build 959 for clinching the title "World’s Fastest Car". Since Ferry Porsche created the first 356, Porsche always makes practical sports cars. Porsche’s cars will never sacrifice handling for top speed, never pursuit acceleration over braking, never place lightness above reliability. Therefore supercar had never been Porsche’s subject.

From the beginning the Porsche 959 project was intended to be a technology study rather than just another supercar. As the company was earning more and more profit from the success of 924 / 944 series, Porsche generously poured in excess of $100 million US dollars into the project, most went to the development of advanced 4-wheel drive, engine, aerodynamics and advanced materials. Porsche believed most of these technologies would benefit production models in the future, or at least keep their engineers state-of-the-art. Now we know only the 4WD system was simplified and applied to the 911 Carrera 4 of 1989.

Anyway, because time and cost were not constraints during the development of 959, no wonder it could be so sophisticated and so well developed.

Development

Basically, the 959 was based on 911’s monocoque chassis but with tracks widened and covered with advanced materials such as Kelvar. The flat six engine was derived from 962’s racing engine. 4WD was a completely new development and was then tested in a 911 Carrera 4x4 in the 1984 Paris-Dakar rally.

The first prototype, named "Group B" rather than "959", was unveiled in the ’83 Frankfurt motor show. It stunned the whole world by its radical specifications but actually it was more a show car than a running prototype. It was called Group B because Porsche designed it to comply with the requirements of FIA Group B racing category. This was, however, never applied.

In the 1985 Frankfurt show, Porsche unveiled a final prototype whose appearance would be carried over to the production car. Most mechanical development was completed, except the complex PSK 4-wheel drive system which met some difficulties. After one year of delay, the first production-ready car was unveiled to journalists in 1986. In April 1987, the first 959 was delivered to Dr. Wolfgang Porsche, the youngest son of Ferry Porsche.

In order to satisfy the minimum requirements of Group B homologation, a limited run of 200 cars was originally planned, but eventually 230 went out of the factory due to strong demand.

Cost

Porsche sold every 959 for $225,000 USD, which could buy a Lamborghini Countach plus a Ferrari Testarossa. Nevertheless, that was still a bargain considering the long list of technology involved - sources estimated the cost of every 959 was $530,000. This means Porsche might made a loss of some $70 million in the production run of 230 cars.

Chassis And Body

Strangely, Porsche 959 was built on a steel monocoque essentially the same as the 911’s. Since all its less expensive rivals like Lamborghini Lamborghini Countach and Ferrari Testarossa Ferrari Testarossa were using the inherently lighter tubular space frame chassis, one can inevitably doubt the effort Porsche had spent on weight reduction. Perhaps Porsche thought any new chassis advancer than steel monocoque could hardly be applied economically to its future production models, so why should it spend money in this subject?

Instead of developing a radical chassis, Porsche pursued lightness by using lightweight materials for body panels.

Styling And Aerodynamic

In fact, 959 was never purposely-styled. Because the chassis came from 911, all the important dimensions and hard points were fixed - the wheelbase was exactly the same as 911, the width exceeded 911 Turbo by 2.5 inches, mostly for accommodating wider tyres. The exterior shape of the cockpit section was nearly identical to its cousin, in which the doors, windows, windscreen and roof even had exactly the same dimensions. No wonder many car tuners could easily modify a 911 into a fake 959!

Initially, it was quite difficult for me to accept its styling - perhaps we were too used to 911’s classical shape so that anything looks half-911 and half-others would be perceived as strange. Honestly speaking, even if we ignored the "911 effect", it still failed to deliver the pure beauty and emotion like any Ferrari Ferrari s. In terms of design philosophy, 959 has none, because it was styled by functional requirements rhater than artistic sense.

One of the functional requirements was aerodynamics. The big front air dam, huge rear spoiler and wide skirts were created step by step in wind tunnel. They contributed to the superb drag coefficient of 0.31 - the best among all supercars (only to be equalled by McLaren F1 and Lamborghini Diablo). This was very crucial to its record-breaking top speed.

Engineers could have reduced the drag further, but they did not want to sacrifice the zero aerodynamic lift they had already achieved. For a supercar running in excess of 300 km/h, any aerodynamic lift could cause serious problems in stability. Obviously 959’s air dam and the fiberglass-Kelvar flat undertray contributed a lot to that.

However, 959 did not create any downforce either, unlike Ferrari F40 and today’s 911 GT1. This explain why it was later discovered as lack of track-racing potential.

Engine

The 2849 c.c. flat-six shared virtually nothing with the 911, because it was derived from the racing unit that powered the 956 and 962 Group C racers. Unlike the famous air-cooled engine using by the contemporary 911, it was water-cooled because the excessive heat generated was impossible to be cooled by air. The basic structure was anything predictable: aluminium alloy head and block, aluminium forged pistons finished with polishing, titanium con-rods, 2 camshafts in each bank driving 4 valves per cylinder, dry sump lubrication .... all operation managed by Bosch’s latest version of Motronic management system.

As in 956 / 962’s engines, it got a pair of small KKK turbochargers. However, they were arranged to operate sequentially for the benefit of responsiveness - below 4,000 rpm, since exhaust gas was not enough for driving both turbines efficiently, all the exhaust gas was fed to a single turbo. This made the turbo operated earlier than conventional turbochargers. Between 4,000 and 4,200 rpm, the second turbo "pre-spin", that is, prepared for engaging very soon. Above 4,200 rpm, two turbos operated simultaneously to provide full boost up to 0.9 bar (12.8 psi). At this moment, or 6,500 rpm, the engine developed the maximum power of 450 hp, which was the highest record for a road car if you do not believe the figure quoted by Lamborghini Countach QV (455 hp).

In contrast, torque seemed to be a little bit disappointed. At 5,500 rpm you got only 369 lbft, well below the 425 lbft of Ferrari F40 Ferrari F40 . Luckily, at least the delivery of torque was quite linear. Since the first turbo started operating hard at 2,500 rpm, no less than 296 lbft was available. It gradually increased until the second phase of boost started at 4,200 rpm, then jumped to the maximum in 5,500 rpm. In short, it had a very good manner for a turbocharged engine of this level of performance.

In order to compensate the lack of torque, as well as to cope with the near-200 mph top speed, Porsche developed a 6-speed gearbox with Borg-Warner.

PSK 4-wheel Drive

This is the highlight of 959’s technology breakthrough.

While other supercar makers insisted to remain rear-wheel drive (mainly for cost and weight concern), Porsche demonstrated the superiority of 4WD with the 959. Those who have ever driven the 959, Bugatti EB110, Ferrari F40, F50, Jaguar XJ220 and McLaren F1 agreed that the first 2 provided much better "real world performance", that is, running on wet or slippery surfaces, or rough twisty roads. Undoubtedly, this is the inherent advantage of 4-wheel drive.

Porsche 959’s PSK (Porsche-Steuer Kupplung) system was like no others. Even in today, it is still regarded as the most sophisticated 4WD system ever made. What made it so unique and so superior? Among all 4WD designs, PSK is the only one which could vary the front / rear torque split ratio under normal running condition, while other designs can only vary when tire slip occurs.

In most of the time, torque split between front and rear was 40 : 60, that is, the same as the car’s weight distribution. This made the best use of traction.

In hard acceleration, PSK transferred up to 80% torque to the rear wheels. Why? Because hard acceleration leads to rearward weight transfer, which reduces traction at front wheels and increases traction at rear wheels. By transferring more torque to the rear wheels, the traction can be optimally used.

On slippery road, 50 : 50 torque slit was used. In any time, computer determined the most suitable torque split ratio by analysing parameters such as throttle position, steering angle, g force and even turbo boost. Therefore PSK system provided near perfect traction that was not comparable by other 4WD systems.

Mechanism

The PSK 4WD system used a multi-plate clutch instead of center differential to carry out the torque split. The clutch had 6 pairs of frictional plate, each pair was independently controlled by computer and actuated by hydraulic pressure. This was simply equal to 6 independent clutches.

To make this system work, the front and rear drive-shafts must run at different speed in normal condition. (so 959 adopted a pair of front tires with 1% larger diameter than the rear’s) Because of the speed difference between front and rear drive-shafts, the 2 frictional plates of each independent clutch were rotating relative to each other. When applied hydraulic pressure to the first clutch, a small amount of torque will transfer to the front axle. But note that the two drive-shafts cannot be fully locked up unless all the 6 clutches are locked simultaneously.

Now, you can see how it worked: locked up 2 clutches, 3 clutches... and the torque to front wheels would be increased, subsequently, torque split could be 50:50 if all the clutches are fully locked up. Of course, all these action was controlled by computer.

This is only for "normal" condition. Like many other 4WD systems, when tire slip occurred, most of the torque could be sent to either axle.

What about energy loss and wear due to the slipping clutches? As the speed difference was very small, Porsche claimed energy loss was no greater than 0.4% of the power developed by the engine. As for wear, the clutch was dimensioned that it was negligible and caused no problem during the whole life span.

Suspensions

The basic suspensions were nothing other than predictable: double wishbones in the front as well as the back. What amazed us were the adjustable ride height as well as the adjustable damping.

The adjustable ride height function was designed to achieve high speed stability without hurting low speed ride. The driver could select a ride height of 12 cm, 15 cm or 18 cm according to need. For example, if the car was traveling off-road, he might need the largest ride height to prevent the car from bottom out or damaging by rocks. If he was just traveling at ease, he might also expect a comfortable ride which was only achievable by the longest suspension travel. However, if he was going to have a 300 km/h excitement in Autobahn highway, he must want the lowest ride height which lowered the center of gravity and stiffened the suspensions (by the shorter suspension travel as well as the adjustable damping) thus enhanced cornering stability.

The 3 ride height settings could be selected manually in the dashboard, or it could be done automatically by the computer. According to Porsche, FOR SAFETY REASON, no matter in what setting the computer would lower the ride height to at most 15 cm when speed exceeded 50 mph and further lowered to 12 cm when exceeding 100 mph. Well, it seemed that Porsche was either regarding its customers as ordinary drivers or it wanted to add another gimmick for advertising purpose. "Computer-controlled self-leveling suspension", doesn’t it sound great?

The adjustable damping also had 3 settings. Of course they varied the damping rate thus result in different stiffness.

To implement the adjustable damping and adjustable ride height, each wheel employed 2 dampers. One of which had an electric motor to vary the damper’s valve system so to implement adjustable damping. Another damper, whose fluid was supplied by hydraulic pump from the engine, took care of the ride height adjustment.

Brakes

Porsche will never increase power without upgrading brakes, especially 959 was the heaviest member of the 911 family and was also by far the fastest. The ventilated discs (in Sport version, also cross-drilled) had diameters of 322 mm and 308 mm front and rear respectively, accompanied with a four-piston aluminum caliper which was yet to be matched then. The four-channel ABS, with sensors on all four wheels, was also the first ABS applied to supercars.

Tires

Strange, very strange .... a German sports car used Japanese tires as standard. Originally, Dunlop promised to development high performance tires specially for 959, but technical difficulties delayed that until the 959 was already launched. Bridgestone, on the other hand, was eager to take part in this project and created the standard rubber earlier than Dunlop.

Strange, very strange .... the rear tires were just 255 mm wide. Ferrari Testarossa was 280 mm, F40 was 335 mm, Lamborghini Countach was even 345 mm!!

One of the reasons was: the PSK 4-wheel drive could optimally use the traction from narrow tires. Another reason was: well, Porsche was actually too conservative. Remember the Bugatti Bugatti EB110 which was also 4-wheel drive and was praised even more in terms of grip? This car had a pair of 325 mm rear rubber.


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