The BMW E31 is the first generation of the BMW 8 Series. It is a grand tourer built by BMW from 1990 to 1999 as a 2-door coupé, powered by either a V8 or V12 engine. Whilst it did supplant the original E24 based 6 Series in 1990, it was not a direct successor, but a new model class with a substantially higher price and performance than the 6 Series.
As a top-of-the-range variant of the 8 Series, the 850CSi took over from the prototype M8 variant. The 850CSi used the same engine as the 850i, which was tuned so significantly that BMW assigned it a new engine code: S70B56. The modifications included Bosch Motronic 1.7 fuel injection, a capacity increase to 5,576 cc (5.6 L) and power increase to 280 kW (381 PS) at 5,300 rpm and 550 N⋅m (406 lbf⋅ft) of torque at 4,000 rpm. Road & Track recorded a 0–60 mph (0–97 km/h) time for the 850CSi of 5.9 seconds.
The 850CSi's modified suspension included stiffer springs and dampers that reduced the car's ride height. The recirculating ball steering ratio was dropped 15% over the standard E31 setup. The model also sported staggered throwing star wheels. The front and rear bumpers were reshaped for improved aerodynamic performance. Four round stainless steel exhaust tips replaced the square tips found on other models. The 6-speed manual gearbox was the only transmission option. In Europe, all 850CSi's came with four-wheel steering (AHK - Aktive Hinterachs-Kinematik, Active rear axle Kinematics), upgraded and ventilated brakes with floating front discs, rear differential oil cooler, engine oil cooler, two-tone interior, sports seats, and reshaped mirrors. In the United States, the cars instead received "BMW Motorsport" writing on the doorhandles.
Production ended in late 1996 because the S70 engine could not be modified to comply with new emission regulations without substantial re-engineering.
