BMW M history
BMW M 850CSi / M8 E31
The BMW 850CSi is the the BMW Motorsport-developed version of the E31 8 Series coupe. It is powered by the S70 V12 engine, a BMW Motorsport-enhanced version the standard production M70 powerplant. In addition, the 850CSi features a BMW Motorsport-tuned chassis and several unique cosmetic items.
|1993-1996 BMW 850CSi E31 Coupe|
S70 B56 Kat
280kW | 381HP
250km/h | 155mph
|Fuel Consumption (l/100km | mpg)|
27.2 | 8.6
12.6 | 18.6
18.0 | 13.0
Source for technical specifications: BMWheaven.
The 850CSi was introduced at the 1991 Frankfurt International Motor Show. The 850CSi was built on the regular 8 Series assembly line at BMW's Dingolfing factory.
Although not badged as as an M car, the 850CSi was developed by BMW Motorsport (later renamed BMW M) and is therefore a true M car.
BMW M8 E31 Prototype
BMW Motorsport did develop a prototype 8 Series with a lightweight body that was known as the M8. Originally envisioned as a Ferrari competitor, 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 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 euro S50B30 BMW M3 engine. The project was eventually scrapped because BMW decided that there was no market for an M8. The only prototype ever produced (one that was reportedly not even road safe) was locked away by BMW in the company's Giftschrank (poison storage) and has reportedly been destroyed.
Instead, a more mild 8 Series with a 24-valve version of the V12 and normal steel body panels was chosen for production. This model was named 850CSi, perhaps because it was more closely related to the regular 850Ci coupe than the M8 prototype or perhaps because BMW did not wish to attach the M badge to a rather large and heavy grand touring coupe.
The "CSi" suffix was first used in 1971 on the E9 3.0 CSi coupe to denote "Coupe Sport injection". It was carried over by the 3.0 CSi's successor, the E24 633CSi (and its successors, the 628CSi, 635CSi and M635CSi). However, in the case of the 8 Series, the CSi suffix is unique to the M-powered version (all other 8 Series models have either an "i" or "Ci" suffix).
Versions and Production Numbers
Three versions of the 850CSi were developed: Two European-spec models (left-hand drive and right-hand drive) and a United States-spec version.
- ECE (LHD): 1,125 built from 08/92 thru 10/96
- ECE (RHD): 160 built from 06/93 thru 06/96
- US (LHD): 225 built from 10/93 thru 06/95
There were no major mechanical changes to the 850CSi during the three and a half years that it was produced. However, the 850CSi did receive a myriad of smaller running changes that affected all 8 Series models. These included the addition of Coded Driveaway Protection (1/95 producton) and revisions to the ABS braking system, door locking system, audio system, on-board computer and other minor equipment changes.
European version vs. U.S. Version
Though lagely similar in specification and appearance, the U.S.-spec 850CSi was denied the following items, largely for cost reasons:
- Engine oil cooler
- Transmission oil cooler
- Active Rear-Axle Kinematics (AHK)
- Upgraded 13.6-inch front brakes rotors, all rotors with "floating" design
- Smoked front turn signal lenses
- M aerodynamic rear-view mirrors
However, U.S. models do include exterior door handles embossed with BMW Motorsport and Extended Yew wood interior trim, both items not normally found on the European-spec version.
When creating the 850CSi's S70 V12 motor, BMW Motorsport began with the standard 24-valve SOHC M70 engine and instituted the following changes:
- Increased bore (from 85mm to 86mm) and stroke (from 79mm to 80mm) for a new total displacement of 5,576cc (from 4,988cc)
- Lighter pistons
- Increased compression (from 8.8:1 to 9.8:1)
- More aggressive valve timing for increased high-rpm power
- Larger diameter exhaust pipes
- Variable rpm limit (6,400 in 1st+2nd, 6,200 in 3rd, 6,100 in 4th. 6,000 in 5th+6th)
- Adjustable throttle sensitivity via dual mode (Sport or Komfort) console-mounted switch
- Engine oil cooler (European-spec models only)
These modifications resulted in an increase in maximum power from 300 hp (DIN) or 296 hp (SAE) at 5,200 rpm to 380 hp (DIN) or 372 hp (SAE) at 5,300 rpm. In addition, maximum torque was increased from 332 lb/ft at 4,100 rpm to 402 lb/ft at 4,000 rpm.This engine can be identified by the "Powered by M" inscription on the central cam cover between the two banks of cylinders.
The sole gearbox offered for the 850CSi was the Getrag Type E six-speed manual with the following ratios: 4.25 (1), 2.53 (2), 1.68 (3), 1.24 (4), 1.00 (5), 0.83 (6). This is mated to a 2.93:1 rear end with limited slip differential. In addition, Automatic Stability Control plus Traction (ASC+T), which can apply the brakes and/or reduce engine power in the event of traction loss, is fitted as standard to the 850CSi. Finally, European-spec models are equipped with a transmission oil cooler.
The 850CSi's chassis is based on that of a normal 8 Series and thus is made up of MacPherson struts in front and a multi-link system that comprises five components (upper transverse link, two lower transverse links, longitudinal link and integral link) in the rear. However, BMW Motorsport specified stronger front hubs, stiffer shocks and shorter springs (by 10mm) for the 850CSi.
In addition, all Euro-spec cars are fitted with Active Rear-Axle Kinematics (known by its German abbreviation AHK for Aktive Hinterachs-Kinematik). The system works by turning the rear wheels in the same direction as the fronts in order to facilitate change of direction and weight shift in a corner. The hydraulically-controlled AHK system activates at speeds above approximately 60 kph (37 mph) and can turn the rear wheels up to 2.5 degrees depending on the angle of the front wheels. See how the AHK systems works:
The 850CSi's steering system is based on the same recirculating ball design as the standard 8 Series but incorporates ZF Servotronic vehicle-speed-sensitive power assist (in place of the usual engine-speed-sensitive system) and a quicker rack (2.8 turns lock-to-lock instead of 3.3 turns).
There are two different braking systems for the 850CSi. European-spec cars are equipped with the same braking system that was fitted to the E34 M5 starting with May, 1994 production. This consists of 13.6-inch vented discs incorporating "floating" rotors and four-piston calipers in the front and 12.8-inch vented discs in the rear. U.S.-spec cars are fitted with the same brakes as the standard five-liter 850i/850Ci: 12.8-inch vented discs in the front and 12.8-inch solid discs in the rear.
Wheels and tires
There were two different wheel and tire packages for the 850CSi. Until early 1995 production, the 850CSi was equipped exclusively with three-piece M System II wheels consisting of a five-spoke forged alloy center and an outer cover in a "throwing star" design. These are sized 8x17-inch in the front and 9x17-inch in the rear with 235/45ZR17 and 265/40ZR17 tires, respectively. As of early 1995 production, 18-inch M Parallel Spoke forged alloy wheels became available, either as an option or as standard equipment depending on the market. The 8x18-inch front wheels are fitted with 245/40ZR18 tires, while the 9.5x18-inch rear wheels carry 285/35ZR18 tires.
Aside from its M-designed 17- or 18-inch wheels, the exterior of the 850CSi is distinguished by a unique front fascia that includes a deeper front airdam and air intake, more pronounced side sills and four round exhaust tips, two pairs on either side of a " diffuser" panel under the bumper. European-spec models also feature aerodynamic M rear-view mirrors, while U.S.-spec cars have unique door handles that are embossed with "BMW Motorsport" script. An "850CSi" badge appears on the trunk lid, but there are no M badges on the exterior of the car.
The interior of the 850CSi shares its basic architecture and design with all 8 Series coupes. The power and heated front seats are identical in shape and function to those fitted to other 8 Series models and include a three-position memory on the driver-side seat. Unlike other 8 Series models, however, the interior of the 850CSi could also be ordered in several two-tone or "Bicolor" Nappa leather combinations (Black/Dark Silvergray, Light Silvergray/Dark Silvergray, Black/Lotus White) in addition to all Black.
Three different airbag-equipped steering wheels were offered depending on the market and production date: a three-spoke design, a four-spoke design (through 8/93 production) and a four-spoke M design with tri-color stitching on the rim (from 9/93 production). A leather shift knob was fitted to every 850CSi while all U.S.-spec models and some later European-spec cars received the leather shift knob with M tri-color stripe.
Every 850CSi also features a special instrument cluster with red needles, a 300 kph/180 mph speedometer and a unique tachometer with a graduated redline (to reflect the variable rev limiter). There are also special plates with the "M" logo on both door sills. The U.S.-spec 850CSi is further distinguished by its standard Yew wood trim on the dashboard, front and rear center consoles, door panels and rear side panels. Several other types of wood trim could be ordered as an option in other markets.
The 850CSi was the flagship of the BMW range and was therefore fitted with most features as standard equipment. Options varied from market to market on Euro-spec cars but generally included various audio and phone systems, a power rear window sunshade, retractable headlight washers, wood trim and (from early 1995) 18-inch M Parallel Spoke wheels. There were no factory options for the U.S.-spec model.
There were no official factory special editions of the 850CSi. However, the 850CSi could be ordered in certain markets outside of North America with the rare "Color-Line" option consisting of coordinated paint and interior trim in one of three monochromatic color schemes (Calypso Red with Calypso Red + Black leather, Tobago Blue with Tobago Blue + Black leather or Barbados Green with Barbados Green + Black leather).
In addition, customers often requested paint, interior trim and/or special equipment from BMW Individual, the branch of BMW M responsible for tailoring vehicles to specific customer requests. Thus, it is fairly common to find examples with items not usually found on the normal equipment list. One extreme example is a special 850CSi built for the painter David Hockney (probably as a gift for having painted the 850CSi Art Car) with an integrated water bowl for his dog between the rear seats.