The automobile is far from the end of its development potential: as Porsche demonstrates with its Type 959. Two years ago it was only a "Group B" study at the IAA, today road tests are underway to prepare for the small series of 200, due for delivery to buyers during 1986. The car shown in September 1985 at the IAA in Frankfurt represents the most advanced state of development but detail changes must still be expected.

Race car technology has been consequently translated into driving safety for a road car. Performance and handling exceed every known yardstick. "Nonetheless," in the words of Porsche Development Chief Helmuth Bott, "the result is a car which provides every comfort, with the smooth running and low interior noise expected of a road car, while offering high safety reserves.

Thus the 959 has an engine which, despite massive power of 450 HP, can be driven elastically in its owerrev ranges. The 959 offers unusual acceleration reserves under all driving conditions, yet it also achieves shorter braking distances than would be possible for a normal automobile. Shock absorber stiffness and ground clearance are adjusted automatically to the most varied demands of low - or high-speed travel.

All-wheel drive with electronic regulation and variable torque division permits optimal driving safety in summer or winter, on dry, wet or slippery surfaces. The anti-block brake system (ABS) is designed for the special conditions of all-wheel drive with differential locks.

Whereas automobile aerodynamics normally aim for minimum coefficient of drag (C_d), the most important criterion in developing 959 bodywork was avoidance of lift. The result is a no-lift vehicle which has virtually the same downforce on its wheels whether speeds are high or low. Even so the coefficient of drag could be reduced to 0.32. In conjunction with a low frontal area this gives very Iow wind resistance. This favorable relationship of C_d to C_L and F has a great deal to do with unusual directional stability as well as ride and braking safety.

Descent From Automobile Racing

Impetus for development of this 959 came from the Group regulations introduced to automobile racing in 1980. These concern competition vehicles of which at least 200 have been built. Porsche wanted to build a car closely related to its production autos, unlike the expensive one-offs of Group C, one equally at home in rallies, races or on the open road. "We couldn't expect to sell 200 cars to active sports drivers alone," Helmuth Bott said. Therefore they made an early decision not to build an expensive special vehicle but to spin the Group B car off an existing model range.

The 911 was ideal for this purpose, as a car which had proven its potential in road use and rallying as well as providing the basis for race sport cars of the earlier Groups 4 and 5. The rear-engine concept was decisive here: Bott explains, "We saw no chance for front-engined cars in Group B, which applies to the Rallye Championship for instance. It has become obvious in rallying that you can only be competitive with an all-wheel-drive vehicle. Thus it was evident at an early date that the requirements were all-wheel drive and descent from a rear - rather than front-engined concept.'

Unlike previous 911 race versions, 934 and 935, development was aimed at a vehicle which could become a test bed for new technology, beyond its roadability. "We decided to fill this car with technical systems which would offer more than any previously known. A series of 200 is an outstanding realm for new developments which might become interesting later for production cars. The all-wheel-drive 911, already planned in any case was included in our discussions from the start. At this point the Board decided to present its project at Frankfurt in 1983 to elicit an echo from the public and Porsche customers. This proved so positive that work went forward at an intensive pace.

First result was the entry of an all-wheel-drive 911 in the 1984 Paris-Dakar Rallye. Unhomologated vehicles are allowed in this extremely difficult rallye, whereas Group B entries are only possible once the series of 200 has been completed. Following an unexpected win in 1984, 1985 provided a further test opportunity for 959 prototypes in the Dakar Rallye. Even though these vehicles didn't reach the finish line this time, having come into violent contact with large boulders, encouraging experience was gained.

New Driving-Safety Technology

Alongside these stiff off-road experiments, road use occupied the foreground of development. Wind tunnel tests ran parallel to design work - first with 1 : 5 models, then 1 : 1 - combined with research into new materials combinations of galvanized sheet steel, aluminum and plastic. This multiple construction style is not only important for development of an optimum aerodynamic and aesthetically beautiful shape, it also keeps body weight as low as possible, necessary in the interests of high performance with Iow fuel consumption.

During this work a path was found, leading to increased driving safety through lift-free aerodynamics. At the same time, the drag coefficient was held to 0.32 through careful detailing, without having to accept lift. Porsche even manages without a separate spoiler: the form of nose and undertray as well as a rear wing integrated into the overall shape, determine aerodynamics and appearance of the 959.

Aerodynamics are closely related to handling in a road vehicle. Such qualities can only achieve full effect. For instance, when ground clearance is adjusted to airflow conditions and held constant. You want minimum ground clearance for driving on a smooth, last surface, while offroad work makes greater clearance necessary. When maneuvering close to curbs or in parking garages one wants to avoid bottoming and possible damage to the floor pan. This was the starting point for development of a speed-related, ride-height control system for the 959. Al high speeds it automatically lowers the car to a value required for safety, while a driver can select his ride height at lower speeds. An additional, top position is provided for special situations such as freeing the car from heavy terrain. This leveling control is handled by an electronically regulated hydraulic system. To ensure driving safety and straight-line stability at high speeds, one must accept firm shock absorber settings. On the other hand, vehicles with sporting shocks are not satisfactory in ride comfort at lower speeds, so an adjustable shock absorber system was included in the 959 Here too, optimum adjustment is maintained automatically at higher speeds. When driving more slowly, a driver can select his adjustment.

Automatic, speed-related control is handled electronically from the speedometer, with function monitored by a warning light. This system is a joint development by Porsche and shock absorber manufacturer Bìlstein.

Variable All-Wheel Drive

When only two wheels are driven in a vehicle with high engine output, they should be loaded wi th the maximum possible share of overall car weight. Even so, it can happen that the drive wheels spin when starting or accelerating, particularly with reduced adhesion. High performance can only be put onto the road safely, despite unfavorable condi- tions, when power is distributed among all four wheels.

This is one of the most important reasons for all-wheel drive gaining ground steadily for rallye cars in recent years. The victory of an all- wheel-drive Porsche 911 in the 1984 Paris-Dakar Rallye proved that even a road-going sports car could compete successfully under the difficult driving conditions of desert and jungle. For this reason, all-wheel drive was a firm part of the Porsche Group B project from the first. All-wheel drive offers clear advantages in competition as well as on the road.

Unlike the Paris-Dakar car, however, a drive system is planned for the 959 which doesn't maintain a constant 50 : 50 power split between front and rear axles at all times. This ratio can be varied to suit changing conditions. Maneuverability under difficult conditions or in winter can be measurably improved with such variable torque split. An additional automatic control also ensures that optimum drive split is available at all times, dependent on dynamic axle loading, meaning changes during acceleration or braking.

To ease parking, drive to the front wheels is reduced at very low speeds. A driver can select positions for conditions such as dry or wet roads ice and snow or difficult terrain. The function of load distribution between the axles is handled by a laminated clutch in the front axle drive housing at the front of the transaxle tube which encloses the drive shaft. This is regulated electronically, delivers corrected torque to the front wheels and functions as a longitudinal lock-up. The rear axle drive unit includes another laminated clutch as transverse lock-up. In the position for difficult terrain, both are locked, giving rigid drive between front and rear wheels as well as within the rear axle. This clutch and its regulation are in-house Porsche developments.

Brakes Wheels, Tires

The braking system of the 959 with vented, four- piston disc brakes parallels Porsche race technology. In addition, these are adjusted to the special conditions of all-wheel operation. The standard anti-block system provides effective balance to the possibilities of all-wheel drive in the acceleration and climbing ranges. It is laid out to remain operational even with a differential locked an important improvement for driving under difficult conditions.

Magnesium wheels with center-lock hubs are another result of race car safety technology. They are designed with hollow spokes whose cavities are directly connected to the air chambers of their tires. The warning light of the tire pressure unit, which lights individually for each wheel in case of pressure loss, thus indicates rim damage as well as a faulty tire. This system was developed in collaboration with Bosch. The Dunlop Denloc, high-speed safety tires provide so much lateral support when pressure is lost that the car remains directionally stable. They are laid out for speeds well above 300 km/h and still offer sufficient slow-driving comfort, in conjunction with adjustable shocks.

This wheel-tire-brake system makes a considerable contribution to the unusual safety reserves of a 959, even in top-speed realms. Low wind resistance makes it possible to accelerate strongly, even from better than 200 km/h. Straight-line stability and short brake distances are comparable to values other vehicles achieve at speeds below 200 km/h.

From Race Engine To Road Power Plant

The technology of turbocharged racing engines has been developed to such a high standard of reliability and smooth operation by Porsche that it suggested a carryover to road use. Further-developed turbo techniques are applied to the 959, allowing unusual elasticity and pulling power even from low revolutions. This 450 HP, 2.85 liter six with four-valve cylinder heads and four camshafts with hydraulic valve lash adjustment, is as quiet mechanically as a touring car engine. It is undemanding in service and meets all legal requirements for normal traffic (augmented EG standard R 15/04) in running manners as well as noise and exhaust emission specifications. It can also be operated on the new, unleaded fuel of 95 octane called Euro-Super with no loss of power.

For sport these 2.85 liters amount to a normally-aspirated displacement of 4 liters, once the turbo handicap factor is applied. This 959 engine is similar to large-volume, unsupercharged engines in power production: turbo lag cannot be detected pulling power is high even at low revs, and increases evenly. With acceleration from 0 to 100 km/h in less than 5 seconds, the 959 stands outside usual limits, yet the car can be driven in thick traffic with no trouble, thanks to its smoothness.

Supercharging by means of two turbochargers with electronic boost pressure regulation and intercoolers is Porsche's own development, electronic ignition and injection by Bosch Motronic has already been used successfully in Porsche race cars. Mixed cooling with water-cooled cylinder heads and proven axial-fan air cooling of the blocks permits useful water heating of the car's interior, as a by-product.

Comfortable Road-Sports Version

The task of the 959 as test bed for safety developments in high-speed realms is particularly obvious in the road-going version. Alongside sporting entries it was planned from the first to offer as many of the 200-series as possible to drivers who take pleasure in an unusual automobile.

The road-sport version of the 959 will meet highest demands in fittings and design: style and selection of materials reflect the clear sporting character of this vehicle, sound-proofing and perfected operational technology ensure pleasant, long-distance driving comfort. Heating and air conditioning are electronically controlled, electric seat adjustment, central locking and electric window lifts are all part of the standard package.

All interior surfaces are carefully designed to match, while only quality materials are used applied by superior handwork standards. Interiors are trimed in leather to match the exterior color, a central console runs forward from the rear seat unit, clear to the dashboard. Switches - among others for leveling, shock absorber adjustment and central locking - are incorporated in a switch panel while all-wheel-drive is pre-selected by a wand on the steering column.

Porsche under lines the purpose of the 959 as a comfortable, safe road-going car with carefully selected, quality fittings. Technical developments put into practice here will serve other Porsche products in the future as well.

MODEL DESCRIPTION: PORSCHE 959

BODYWORK

Aerodynamically optimized body with enclosed underbody. Exterior skin of plastic (Aramid fiber compound) bonded by the autoclave technique. Front skirt of polyurethane (PU). Front lid and doors of aluminum. Load-bearing body structure of fired-zinc sheet steel.

ENGINE

Engine type:	6 cylinder. four-stroke, Otto engine with light alloy crankcase, individual light alloy cylinders and one light alloy cylinder head for each bank.
Lubrication:	Dry sump lubrication with separate oil tank and oil cooler.
Cooling:	Fan-air colling for cylinders liquid cooling for cylinder heads.
Control:	4 overhead valves in vee per cylinder with hydraulic valve lash adjustment, two camshafts on each side. chain-driven
Fuel:	Lead-free gasoline Euro-Super (RON 95) or leaded super.
Fuel system:	Individual-cylinder injection via 2 injectors per cylinder with digital engine electronics. Mass flow sensing by pressure measurement in intake plenum.
Ignition system:	Digital engine electronics (engine map controlled).
Supercharging:	2 exhaust turbochargers with water-cooled bearing housing, staged turbo pickup, 2 air-air intercoolers, electronic absolute-pressure boost regulation with bypass valve and turbine cut-in valve

TECHNICAL ENGINE DATA

Cylinder count and arrangement:	6 boxer
Stroke:	67 mm
Bore:	95 mm
Displacement:	2.850 cc
Compression ratio:	8.0
Max output: at engine revs:	331 kW / 450 HP 6500 RPM
Max torque: at engine revs:	500 Nm 5500 RPM

GEARBOX

All-wheel drive with program switch transaxle construction style. Electronically controlled longitudinal clutch. Electronically controlled rear axle lock-up. 6 speed gearbox.

CHASSIS

Wheels:	Hollow-spoke, magnesium wheels with center-lock hubs
Tires:	Front: 8 J x 17 235/40 VR 17 Rear: 9 J x 17 255/40 VR 17
Suspension:	Dual transverse arms and dual shock absorbers front and rear
Shock stiffness:	Adjustable from driver's seat
Brakes:	4 piston brake calipers (race technology). Hydraulic brake boost and anti-block control system (Porsche Wabco).
Vehicle height:	Adjustable from driver's seat

FITTINGS

Seats adjusted electrically, electric window lifts, water heating with automatic regulation air conditioner with automatic regulation, radio with four loudspeakers, central locking.

PRICE

DM 420.000.-