01 · Overview
The Gran Turismo that came too early
In September 1989, BMW presented the 850i at the IAA: a coupé without a B-pillar, with pop-up headlights, a twelve-cylinder engine and a drag coefficient of 0.29 — the best a full-fledged coupé in this performance class achieved at the time. The E31 was the brand’s flagship model and, at 135,000 marks, more expensive than any BMW before it.
It was not the first BMW with a V12 — that had existed since 1987 in the 750i. But it was the first production car in the world to combine a twelve-cylinder engine with a six-speed manual gearbox, and it introduced the newly developed Integral rear axle. Technically, it was BMW’s showcase.
Commercially, it never became that. Recession, the Gulf War and rising energy prices hit the model line immediately after launch; in 1993 BMW added the cheaper eight-cylinder 840Ci, withdrew from North America in 1997 and ended production in May 1999. 30,603 vehicles in ten years — the predecessor 6 Series had managed 86,216 in fourteen years. There was no successor for almost twenty years.
02 · History
Ten years in ten steps
From the IAA premiere to discontinuation without a successor.
- 1989 World premiere of the 850i at the IAA in Frankfurt in September, production start in May. Base price 135,000 marks.
- 1990 Series production begins at the Dingolfing plant. From spring, Electronic Damper Control EDC becomes available.
- 1991 Three Convertible prototypes are built and abandoned: too heavy, not stiff enough, too expensive. An open-top 8 Series never happened.
- 1992 The 850CSi arrives as the flagship model — 5.6 litres, 380 hp, manual transmission only, 180,000 marks. In parallel, 18 test vehicles of the 830i are built, which are never sold.
- 1993 With the 840Ci, an eight-cylinder entry-level model arrives in July for 129,000 marks. The base model is now called 850Ci.
- 1994 Facelift: the new 5.4-litre V12 M73 replaces the M70 in the 850Ci, 326 hp instead of 300 hp. The M70 era ends in October.
- 1995 David Hockney designs the fifteenth BMW Art Car based on an 850CSi.
- 1996 The 840Ci receives the 4.4-litre M62 — same power, more torque. The 850CSi is discontinued in November.
- 1997 BMW withdraws the 8 Series from the North American market.
- 1999 End of production in May after 30,603 series vehicles. A successor does not arrive until 2018 with the G15.
03 · Model overview
From the 840Ci to the 850CSi
Six production variants, two engine families. Caution with two designations: depending on the model year, “850Ci” refers to two different twelve-cylinder engines, and the four-litre V8 is listed as 840i in parts catalogues, while in sales it was called 840Ci.
Source: factory and literature data · verified
Technische Daten anzeigen — komplette Modellmatrix
| Modell | Motor | Hubraum | Leistung | Bauzeit |
|---|---|---|---|---|
| 840Ci | M60B40 · V8 | 3.982 cm³ | 286 PS (210 kW) | 1993–1996 |
| 840Ci | M62B44 · V8 | 4.398 cm³ | 286 PS (210 kW) | 1995–1999 |
| 850i | M70B50 · V12 | 4.988 cm³ | 300 PS (220 kW) | 1989–1992 |
| 850Ci | M70B50 · V12 | 4.988 cm³ | 300 PS (220 kW) | 1993–1994 |
| 850Ci | M73B54 · V12 | 5.379 cm³ | 326 PS (240 kW) | 1994–1999 |
| 850CSi | S70B56 · V12 | 5.576 cm³ | 380 PS (280 kW) | 1992–1996 |
| 830i (test vehicle) | M60B30 · V8 | 2.997 cm³ | 218 PS (160 kW) | 1992 · 18 units, never sold |
04 · Body variants
Body variants
Coupé
The only production body: two-door, without B-pillar, with frameless windows that automatically lower slightly when the door is opened.
Convertible (prototype)
Three prototypes were built in 1990/91 and abandoned — too heavy, not stiff enough, too expensive. There was never a production Convertible of the E31.
05 · Engines
Two engine families, four twelve-cylinder stages
The E31 launched with the M70, the first German post-war twelve-cylinder engine in large-scale production, which had debuted a year earlier in the 750i. M GmbH developed the S70 of the 850CSi from it. From 1993, the eight-cylinder M60 was added, and from 1994 the final V12 stage, the M73. No E31 engine has a timing belt — all run on a timing chain.
M70B50 — 850i and 850Ci up to 1994 verified
BMW's first production twelve-cylinder engine, introduced in 1987 in the 750i. Deliberately conservative design: two valves per cylinder, timing chain instead of belt, Alusil cylinder bores. Two separate Motronic control units, one per bank.
Technische Daten anzeigen
| Bauart | V12, 60 degrees, OHC, 2 valves per cylinder |
| Hubraum | 4.988 cm³ |
| Bore × stroke | 84,0 × 75,0 mm |
| Verdichtung | 8,8 : 1 |
| Gemischaufbereitung | 2 × Bosch Motronic, bank-separated |
| Leistung | 300 hp (220 kW) at 5,200 rpm |
| Drehmoment | 450 Nm at 4,100 rpm |
BMW Group Classic, Wikipedia · Dyno: verified
M73B54 — 850Ci ab 1994 verified
The final development stage of the large twelve-cylinder, used in parallel in the 7 Series E38 and later in the Rolls-Royce Silver Seraph. More displacement, more torque, same basic architecture.
Technische Daten anzeigen
| Bauart | V12, 60 degrees, SOHC, 2 valves per cylinder |
| Hubraum | 5.379 cm³ |
| Bore × stroke | 85,0 × 79,0 mm |
| Leistung | 326 hp (240 kW) at 5,000 rpm |
| Drehmoment | 490 Nm at 3,900 rpm |
BMW Group Classic, Wikipedia · Dyno: verified. Compression ratio of 10.0 : 1 documented by only one source.
S70B56 — 850CSi verified
The M development stage of the M70: larger bore, longer stroke, higher compression, electronic throttle. Not to be confused with the S70/2 of the McLaren F1 — that is a different engine with four valves per cylinder and 6,064 cm³.
Technische Daten anzeigen
| Bauart | V12, 60 degrees, OHC, 2 valves per cylinder |
| Hubraum | 5.576 cm³ |
| Bore × stroke | 86,0 × 80,0 mm |
| Verdichtung | 9,8 : 1 |
| Gemischaufbereitung | 2 × Bosch Motronic, electronic throttle |
| Leistung | 380 hp (280 kW) at 5,300 rpm |
| Drehmoment | 550 Nm at 4,000 rpm |
BMW Group Classic, BMW M, Wikipedia · Dyno: verified. Figures of 375 and 381 hp in secondary sources are rounding variants of 280 kW.
M60 and M62 — 840Ci verified
The eight-cylinder made the 8 Series more accessible in 1993: the same power as at its replacement in 1996, but more torque and a noticeably lighter front end than with the twelve-cylinder.
Technische Daten anzeigen
| Bauart | V8, 90 degrees, DOHC, 4 valves per cylinder |
| M60B40 | 3.982 cm³ · 286 PS (210 kW) · 400 Nm |
| M62B44 | 4.398 cm³ · 286 PS (210 kW) · 420 Nm |
| Steuertrieb | Steuerkette |
| Laufbahnen | M60 early Nikasil, later Alusil |
BMW Group Classic, Wikipedia · Dyno: verified. The English Wikipedia states 400 Nm for the M62B44 — the correct figure is 420 Nm.
06 · Weak points
Reliability & weak points
- Electronics are the core risk. The V12 has two separate engine control units along with dual fuel pumps and sensors, plus body, climate control, transmission and chassis control units. Individual components cost four figures, some are no longer available.
- Pixel failure in the instrument cluster and on-board computer is to be expected on virtually every vehicle. Repair is significantly cheaper than replacement.
- Nikasil in the early eight-cylinder: the M60 in the 840Ci from 1993 to 1995/96 can lose compression with high-sulphur fuel. Mainly affected were the US and the UK, while continental Europe is considered largely spared. Detectable via compression test and the block’s casting number.
- Cooling system in the twelve-cylinder: cracking expansion tanks, failing water pumps and viscous couplings. Overheating here leads to follow-on costs that can exceed the vehicle’s value.
- Hydraulic brake booster with ball-type pressure accumulator in early vehicles. After thirty years, the seals are worn out, and the original part costs four figures.
- Suspension bushings are wear items under two tonnes of mass — six to seven joints per side, an overhaul beyond 150,000 kilometres is the norm.
- The Active Rear-Axle Kinematics of the 850CSi is expensive and partly no longer available; many vehicles have a deactivated system.
07 · Engineering
Chassis, drivetrain, brakes, electronics
Fahrwerk
Antrieb
Bremsen
Elektronik
Technical data — final drive ratios & gearboxes
- Transmission 850i with M70
- six-speed manual Getrag 560G or four-speed automatic ZF 4HP24
- Transmission 850Ci with M73 from 1994
- five-speed automatic ZF 5HP30, the six-speed manual remained in the lineup
- Transmission 840i and 840Ci
- six-speed manual Getrag 420G or torque converter automatic; automatic only in the US
- Transmission 850CSi
- exclusively a six-speed manual with its own gear ratios and separate transmission oil cooling
- Final drive ratio 850CSi
- 2.93 with limited-slip differential
Except for the 850CSi, all E31 final drive ratios rely on a single source; no leading source publishes E31 axle data. For this reason, only the documented value is given here.
For the 840i, the figures for the automatic transmission are contradictory: one source states four speeds, while the English Wikipedia states a five-speed automatic ZF 5HP24 for the V8.
08 · Top models
Top models
Each of these models gets its own subpage. Here are the short profiles.
850CSi
The flagship model from M: 5.6 litres, 380 hp, rear-axle steering, manual only, 1,510 units.
To the sub-page →
850i
The origin — and the world's first production car with a twelve-cylinder engine and six manual gears.
To the sub-page →
840Ci
The eight-cylinder entry-level model from 1993. Lighter, more economical, today the most accessible E31.
To the sub-page →
09 · Special Editions & Tuners
The M8 that never was — and the McLaren legend
A production M8 never existed. Around 1990, M GmbH built a single running example: body without pop-up headlights, carbon-fibre parts, plexiglass windows, racing seats, under 1,450 kilograms — and a twelve-cylinder engine of around six litres, four valves per cylinder and individual throttle butterflies. Recession and a sales slump ended the project; BMW brought the less radical 850CSi instead. The prototype disappeared for around two decades and was only shown publicly in 2010.
There are two figures for its output, and both come from BMW itself: the PressClub stated around 550 hp in 2014, while bmw-m.com states 640 hp at 7,500 rpm. The higher figure matches exactly the data set of the McLaren F1 engine — displacement, torque and rpm agree down to the decimal point. We therefore present both values without confirming either as definitive.
And with that, to the most persistent legend: the V12 of the McLaren F1 is not the engine of the 8 Series. The S70B56 of the 850CSi is a bored-out M70 with two valves per cylinder and 5,576 cm³. The S70/2 of the McLaren has four valves per cylinder, 6,064 cm³, a different compression ratio and a different rev range — a new design. What they share is the department, the engineer Paul Rosche and the technology concept. Not the construction.
Alpina built the B12 5.0 based on the E31 with 350 hp (97 units, 1990–1994) and the B12 5.7 based on the 850CSi with 416 hp and a carbon bonnet (57 units, from 1992).
10 · Buying guide
What matters: electronics before bodywork
The E31 reverses the usual classic-car logic. The body is comparatively rust-resistant, the risk lies in the electronics and hydraulics. And it is the textbook example of the cheap car becoming the most expensive one: vehicles at the lower end often need another purchase price’s worth of money to get right. The rust spots that do occur nonetheless:
Lower door edges and the rear corners of the doors
Bottom of the battery box in the boot, if the seals leak
Rear wheel arches, especially with flared or widened edges
Windscreen frame and roof edge
Sunroof frame, along with misaligned adjustment and sealing issues
Not bodywork, but expensive: corrosion on the high-pressure lines of the rear-axle steering
The parts situation is split in two. Much is available through BMW Classic and the club catalogue, at premium prices — but for V12-specific parts, CSi body parts and the rear-axle steering, certain items are no longer available from the manufacturer. Both major buyer’s guides arrive at the same advice: buy the best car you can find, not the cheapest.
11 · The competition
What the E31 had to measure up against
Mercedes-Benz SL (R129)
Introduced at the same time and likewise a technological showcase — the most direct German rival, explicitly named as such by BMW.
Mercedes-Benz S-Class Coupé (C140)
The true format equivalent: a two-door luxury GT with a twelve-cylinder engine, even heavier and even more expensive.
Jaguar XJS
The classic British twelve-cylinder GT that the 8 Series was meant to succeed — conceptually the closest relative, technically a generation older.
Porsche 928
The only German competitor with a comparable claim to driving dynamics, transaxle layout and front-mounted V8.
Aston Martin Virage
A hand-built British counter-design in the same price bracket, listed by BMW as a competitor.
12 · Galerie
An 850Ci in detail
Original photographs of a BMW 850Ci in Hellrot — body, wheels and the twelve-cylinder engine. The vehicle shown is an 850Ci, not the 850CSi from the flagship models section.
13 · Sources
Belege & Literatur
Every figure on this page is backed by a source and a dyno check. Basic rule: anything not from BMW or Wikipedia requires at least two independent sources. We flag contradictory values rather than smoothing them over — with the M8 prototype, BMW even contradicts itself.
- BMW Group Classic — 8 Series model line (E31) as well as the model pages 850i, 850Ci, 850CSi and 840Ci
- BMW PressClub — Timelessly fascinating: 25 years of the BMW 8 Series
- BMW M — The BMW 850 CSi (E31)
- BMW M — The BMW M8 (E31) Prototype
- Wikipedia — BMW E31
- Wikipedia — BMW M70, M60, M62 and M73
- Hagerty — BMW 8 Series are spiking in value (US market, 2018)
- classic.com — auction database BMW 8 Series (E31), US market
- Classic & Sports Car — Buyer's guide BMW 8 Series
- auto motor und sport — Buyer's guide BMW 8 Series (E31)
- e31.net — technical data for the E31 model line, final drive ratios by model and transmission