The BMW M635CSi, produced from 1984 to 1987, represents the high-performance variant of the E24 6 Series coupe. Positioned as the flagship of the 6 Series range, it was BMW’s answer to grand touring cars like the Porsche 911. The “M” designation signified its development by BMW’s Motorsport division, resulting in significant upgrades over the standard 635CSi. This model is particularly notable for its sophisticated engine technology and balanced handling, establishing a benchmark for sporting coupes of its era. It was a key model in cementing BMW’s reputation for building driver-focused luxury vehicles.
Technical Specifications
| Brand | BMW |
| Model | 6 Series |
| Generation | 6 Series (E24, facelift 1982) |
| Type (Engine) | M 635CSi (286 Hp) |
| Start of production | 1984 |
| End of production | 1987 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Coupe |
| Seats | 4 |
| Doors | 2 |
| Fuel consumption (economy) – urban | 16.5 l/100 km (14.3 US mpg, 17.1 UK mpg, 6.1 km/l) |
| Fuel consumption (economy) – extra urban | 7.8 l/100 km (30.2 US mpg, 36.2 UK mpg, 12.8 km/l) |
| Fuel consumption (economy) – combined | 11.3 l/100 km (20.8 US mpg, 25 UK mpg, 8.8 km/l) |
| Fuel Type | Petrol (Gasoline) |
| Acceleration 0 – 100 km/h | 6.4 sec |
| Acceleration 0 – 62 mph | 6.4 sec |
| Acceleration 0 – 60 mph | 6.1 sec |
| Maximum speed | 255 km/h (158.45 mph) |
| Weight-to-power ratio | 5.2 kg/Hp, 190.7 Hp/tonne |
| Weight-to-torque ratio | 4.4 kg/Nm, 226.7 Nm/tonne |
| Power | 286 Hp @ 6500 rpm |
| Power per litre | 82.8 Hp/l |
| Torque | 340 Nm @ 4500 rpm (250.77 lb.-ft. @ 4500 rpm) |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | M88 |
| Engine displacement | 3453 cm3 (210.71 cu. in.) |
| Number of cylinders | 6 |
| Engine configuration | Inline |
| Cylinder Bore | 93.4 mm (3.68 in.) |
| Piston Stroke | 84 mm (3.31 in.) |
| Compression ratio | 10.5:1 |
| Number of valves per cylinder | 4 |
| Fuel injection system | Multi-port manifold injection |
| Engine aspiration | Naturally aspirated engine |
| Engine oil capacity | 5.8 l (6.13 US qt | 5.1 UK qt) |
| Coolant | 12 l (12.68 US qt | 10.56 UK qt) |
| Kerb Weight | 1500 kg (3306.93 lbs.) |
| Max. weight | 1850 kg (4078.55 lbs.) |
| Max load | 350 kg (771.62 lbs.) |
| Trunk (boot) space – minimum | 335 l (11.83 cu. ft.) |
| Fuel tank capacity | 70 l (18.49 US gal | 15.4 UK gal) |
| Length | 4755 mm (187.2 in.) |
| Width | 1725 mm (67.91 in.) |
| Height | 1355 mm (53.35 in.) |
| Wheelbase | 2625 mm (103.35 in.) |
| Front track | 1430 mm (56.3 in.) |
| Rear (Back) track | 1464 mm (57.64 in.) |
| Drag coefficient (Cd) | 0.39 |
| Drivetrain Architecture | The Internal combustion engine (ICE) drives the rear wheels of the vehicle. |
| Drive wheel | Rear wheel drive |
| Number of gears and type of gearbox | 5 gears, manual transmission |
| Front suspension | Independent, type McPherson with coil spring and anti-roll bar |
| Rear suspension | Independent coil spring |
| Front brakes | Ventilated discs |
| Rear brakes | Disc |
| Steering type | Cone worm with recirculation balls |
| Tires size | 195/70 R14 |
| Wheel rims size | 6.5J x 14 |
Powertrain & Engine Architecture
The heart of the M635CSi is the M88 inline-six engine, a direct descendant of the engine used in the BMW M1 supercar. Displacing 3.5 liters (3453 cc), this engine featured a cast iron block and an aluminum cylinder head. It utilized a Bosch Motronic fuel injection system and four valves per cylinder, contributing to its high output. The M88 produced 286 horsepower at 6500 rpm and 340 Nm (250.77 lb-ft) of torque at 4500 rpm. This engine was known for its smooth power delivery and willingness to rev. The M635CSi was exclusively offered with a five-speed manual transmission, providing precise control and enhancing the driving experience. The transmission was robustly built to handle the engine’s power and torque.
Driving Characteristics
The M635CSi offered a compelling blend of performance and refinement. Acceleration from 0 to 60 mph was achieved in approximately 6.1 seconds, and it could reach a top speed of 158.45 mph. The car’s handling was precise and balanced, thanks to its well-tuned suspension and rear-wheel drive layout. The McPherson strut front suspension and independent coil spring rear suspension provided a comfortable ride while maintaining excellent body control. Compared to the standard 635CSi, the M635CSi felt significantly more responsive and engaging, with noticeably stronger acceleration and improved handling. The manual transmission allowed for full control over the engine’s power, making it a rewarding car to drive on both the road and the track.
Equipment & Trim Levels
The M635CSi came standard with a comprehensive list of features, reflecting its status as a premium grand tourer. Interior appointments included leather upholstery, power windows, central locking, and an upgraded sound system. Sport seats provided excellent support during spirited driving. Optional extras included a sunroof, air conditioning, and a limited-slip differential, further enhancing the car’s performance and comfort. The exterior featured unique aerodynamic enhancements, including a rear spoiler and revised front and rear bumpers, distinguishing it from the standard 6 Series models.
Chassis & Braking
The M635CSi’s chassis was reinforced compared to the standard 6 Series to handle the increased power and stresses of high-performance driving. It featured ventilated disc brakes on all four wheels, providing ample stopping power. The steering was a recirculating ball system, offering precise control and feedback. The suspension was tuned for a balance between comfort and handling, with stiffer springs and dampers than the standard 635CSi. The car rode on 6.5J x 14 inch wheels with 195/70 R14 tires.
Market Reception & Comparison
The M635CSi was widely praised by automotive journalists for its performance, handling, and refinement. It was considered a worthy competitor to the Porsche 911 and other high-performance coupes of the era. Critics noted its smooth engine, precise handling, and comfortable interior. Compared to the standard 635CSi, the M635CSi offered a significant performance upgrade, but it also came with a higher price tag. Fuel economy, while not a primary concern for buyers of this type of vehicle, was reasonable for a high-performance coupe of its time, averaging around 20.8 US mpg combined.
Legacy
The BMW M635CSi remains a highly sought-after classic car today. Its combination of performance, refinement, and timeless styling has made it a favorite among collectors and enthusiasts. The M88 engine is known for its durability and reliability, although regular maintenance is essential to keep it in top condition. Well-maintained examples of the M635CSi command high prices in the used car market, reflecting their rarity and desirability. The M635CSi is considered a landmark vehicle in BMW’s history, representing the pinnacle of 1980s grand touring performance.
