Porsche 959 1987-1988

 At the 1983 IAA Frankfurt Motor Show, Porsche unveiled a Concept car with the designation "Group B". Introduced in 1982, the Group B was defined under FIA racing rules as competition vehicles in sportscar racing and rallyes regulated by the Federation Internationale de l'Automobile. The Group B regulations resulted in some of the most powerful and quickest machines for official racing events. It was a replacement for Group 4 dedicated to modified grand touring and Group 5 for touring prototypes.

The Porsche Group B will go through intense development by participating in most demanding racing events like Paris Dakar Rallye Raid (1986 overall win)  and Pharaoh Rallye (1985 win)  or Le Mans 24 Hours (7th overall in 1986- under designation Porsche 961).

It will enter in limited production starting in 1987.

Initially conceived for motor racing in Group B, this supersports 911 was designed and built without any economic restraints, the brief being to use the very best components and mate­rials in every respect regardless of cost. The result was a four-wheel drive high-performance sports car, a cutting-edge achievement in technology with 450 bhp engine output and a top speed of 315 km/h or 195 mph. This, obviously, came at a price, 292 units in this small production series selling in the market for a hefty but fully justified DM 420,000.–.

Porsche 959 Biturbo engine description

Biturbo multistage supercharging - This variant based on the 911 short block was developed for use according to the Class B sporting rules. Based on the handicap factor of 1.4 that applied here for turbo engines, the displacement was specified at 2849.5 cc, in order to be eligible to line up in the 4-litre class. The reduced displacement compared with the Porsche 911 turbo 3.3, which in particular significantly influenced the torque characteristic, was more than compensated for by the use of two identically sized turbochargers arranged in series. The new multistage supercharging design not only assured greater output, but in particular also smooth and powerful acceleration from low engine speeds.

The multistage arrangement solved the conflict between excellent acceleration with a small exhaust-gas turbine and high maximum output with a large exhaust-gas turbine. The first supercharger is in operation throughout the entire engine speed range. In the lower engine speed range the entire exhaust-gas flow is routed over it. Basically the two additional components, turbine sequence valve and compressor sequence valve, regulate the transition from single charger operation to double charger operation.

The process is controlled by microprocessor. In the regulated single charger mode the turbine sequence valve acts as a charge-air pressure controller, by routing excess exhaust-gas energy to the second turbine thus inducing this to run up. During this transition phase the compressor sequence valve however, ensures that the air supplied by this second compressor is routed over the vent valve upstream of the first compressor, whereupon it is then aspirated by it. Not until at high speed, when the exhaust-gas energy is sufficient for both exhaust-gas turbochargers, are both the turbine sequence valve and the compressor sequence valve fully opened, whereupon the two exhaust-gas turbochargers then share the workload equally. The charge-air pressure control is then performed conventionally by means of a bypass valve. Charge air is routed by way of a cooler each to the water-cooled four-valve cylinder heads. The difficult space conditions prevalent in the four-valves per cylinder technology not only require water cooling, but also renders the use of spark plugs with smaller diameters necessary. Ignition and injection timing is performed by a pressure-controlled Bosch Motronic, i.e. a piezoelectric pressure sensor provides the load signal without any loss of throttle, which is then corrected by the charge-air temperature. The forged titanium conrods of this power unit developing 450 hp/ 331 kW at 6500 rpm are fully polished and the seven-bearing steel crankshaft is gas nitrated. Built: 1987 to 1988

Wallpapers of the Porsche 959 1987-1988 (click on image to enlarge)