1988: All-wheel drive
Porsche gained extensive experience of using all-wheel drive in a sports car with the Type 959, a technology demonstrator in every respect. Produced in low numbers as a special series, its influence could be seen in its successor, Porsche’s first series production all-wheel drive sports car, the 911 Carrera 4, which was introduced in 1988. For excellent driving dynamics, the 959 had an electronic, infinitely variable centre-differential lock, and torque was distributed to the two axles depending on the wheel-load distribution and the friction coefficients of the wheels on the road. For the same purpose, the engineers then set up the Carrera 4 with a basic torque distribution of 31 to 69 per cent (front axle to rear axle) via a planetary transfer gear. The car also featured a hydraulically operated centre and axle differential lock for virtually infinite adjustment of the distribution ratio. Their function was controlled by an electronics system integrated into the ABS control unit. The next Carrera 4, introduced in 1994, represented the next evolutionary stage of the Porsche all-wheel drive. For example, it was fitted with an optimally adapted, very light viscous multi-plate clutch as the axle clutch.