Design of the 8 Series began in 1984, with construction starting in 1986. The 8 Series debuted at the Frankfurt Motor Show (IAA) in early September 1989. The 8 Series was designed to move beyond the market of the original 6 Series. The 8 and 6 Series cars had very different character: while the 6 Series was a solid Grand Touring car, the 8 Series was designed as a direct competitor to the upcoming Mercedes SL. It was BMW's flagship car while in production.
Over 1.5 billion Deutschmark were spent on total development (2005 USD $2.2 billion). BMW used CAD tools, still unusual at the time, to design an all-new body. Combined with wind tunnel testing, the resulting car had a drag coefficient of 0.29, a major improvement from the previous BMW M6/635CSi's 0.39.
M8One of BMWs best kept secrets is the cancelled BMW M8 Prototype. Originally envisioned as a Ferrari killer, only a single prototype was ever produced, equipped with a special 550 bhp (410 kW) version of the S70 engine, essentially a bored out version of the M70 with experimental multi valve cylinder heads. A very common misconception is that this engine eventually ended up in the McLaren F1. However when this was suggested to McLaren's designer Gordon Murray, the idea was rejected because the engine was overweight and too long for the McLaren F1. A whole new engine was designed which has a closer resemblance to the later S30B30 BMW M3 engine. The mix up occurs as the McLaren engine got the confusing engine code S70/2.
Details about the M8 prototype are very sketchy, the project was eventually scrapped because BMW have decided that a market for such a car as the M8 did not exist. The only prototype ever produced (one that was reportedly not even road safe) was locked away by BMW in their Giftschrank (poison storage) and has reportedly been destroyed[1].
While the M8 was never produced, it is interesting to note that the 850CSi was also tuned by the M division and aside from sporting an M-tuned engine (as identified by the S suffix instead of the M prefix that a true M car would wear), the car's VIN would identify the car as being built by BMW Motorsport (identified by the WBS prefix) instead of BMW AG (WBA prefix). This effectively identifies the 850CSi as a sort of detuned version of the M8[2].
There has been some confusion, as owners of standard 8-series occasionally have been seen to somehow procure realistic looking "M8" badges for their cars. No matter how professional it looks, the M8 was never produced and thus does not exist on the road.
Alpina B12BMW tuner Alpina produced a special version of the 8-Series dubbed the B12. Two versions were produced, both taken from the standard production line, the B12 5.0 Coupe was based on the 850i powered by the 5.0 liter M70 engine producing 350 bhp (260 kW) and available only with a 4-speed automatic gearbox meanwhile the larger B12 5.7 Coupe was based on the 850CSi with the 5.7 liter S70 engine producing 416 bhp with a 6-speed manual gearbox. All in all 97 5.0 Coupes and 57 5.7 Coupes were built, all were built from existing units and their numbers do not add up to the total number of E31s built. The last of these very rare and infamous Alpinas were created in 1999, only 12 units were produced in specially custom made shades of color and revamped interiors. Those 12 units were specifically made for the sheiks of the U.A.E. at their request and to locate one for sale would be quite amazing as it is known that a few units were damaged in accident.
Alpina B12 5.7
http://www.youtube.com/watch?v=0djoyLE1moUhttp://www.youtube.com/watch?v=1HjGTYNNEVo 
BMW E31- 8 Series, 830Ci, 840Ci, 850Ci/CSi, M8, Alpina B12.
