The BMW 6 Series Convertible (E64) 645Ci, produced from 2003 to 2005, represented BMW’s foray into the luxury roadster market with a focus on grand touring. Positioned as a premium offering within the E64 generation, which spanned from 2003-2010, the 645Ci aimed to blend performance, luxury, and open-air driving enjoyment. It was built on the BMW E63/E64 platform, sharing underpinnings with the 5 Series (E60) sedan but distinguished by its two-door convertible body style and more powerful engine options. The 645Ci served as a stepping stone to the higher-performance 650i, offering a compelling balance of power and refinement for discerning buyers.
Technical Specifications
| Brand | BMW |
| Model | 6 Series |
| Generation | 6 Series Convertible (E64) |
| Type (Engine) | 645Ci (333 Hp) |
| Start of production | 2003 |
| End of production | 2005 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Cabriolet |
| Seats | 4 |
| Doors | 2 |
| Fuel consumption (urban) | 18.5 l/100 km (12.7 US mpg, 15.3 UK mpg, 5.4 km/l) |
| Fuel consumption (extra urban) | 9.6 l/100 km (24.5 US mpg, 29.4 UK mpg, 10.4 km/l) |
| Fuel consumption (combined) | 12.9 l/100 km (18.2 US mpg, 21.9 UK mpg, 7.8 km/l) |
| Fuel Type | Petrol (Gasoline) |
| Acceleration 0 – 100 km/h | 6.1 sec |
| Acceleration 0 – 62 mph | 6.1 sec |
| Acceleration 0 – 60 mph | 5.8 sec |
| Maximum speed | 250 km/h (155.34 mph) |
| Emission standard | Euro 4 |
| Weight-to-power ratio | 5.5 kg/Hp, 183.5 Hp/tonne |
| Weight-to-torque ratio | 4 kg/Nm, 247.9 Nm/tonne |
| Power | 333 Hp @ 6100 rpm |
| Power per litre | 75.7 Hp/l |
| Torque | 450 Nm @ 3600 rpm (331.9 lb.-ft. @ 3600 rpm) |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | N62B44 |
| Engine displacement | 4398 cm3 (268.38 cu. in.) |
| Number of cylinders | 8 |
| Engine configuration | V-engine |
| Cylinder Bore | 92 mm (3.62 in.) |
| Piston Stroke | 82.7 mm (3.26 in.) |
| Compression ratio | 10:1 |
| Number of valves per cylinder | 4 |
| Fuel injection system | Multi-port manifold injection |
| Engine aspiration | Naturally aspirated engine |
| Valvetrain | DOHC |
| Engine oil capacity | 8 l (8.45 US qt | 7.04 UK qt) |
| Coolant | 13.8 l (14.58 US qt | 12.14 UK qt) |
| Kerb Weight | 1815 kg (4001.39 lbs.) |
| Max. weight | 2215 kg (4883.24 lbs.) |
| Max load | 400 kg (881.85 lbs.) |
| Trunk (boot) space – minimum | 300 l (10.59 cu. ft.) |
| Trunk (boot) space – maximum | 350 l (12.36 cu. ft.) |
| Fuel tank capacity | 70 l (18.49 US gal | 15.4 UK gal) |
| Length | 4820 mm (189.76 in.) |
| Width | 1855 mm (73.03 in.) |
| Height | 1373 mm (54.06 in.) |
| Wheelbase | 2780 mm (109.45 in.) |
| Front track | 1558 mm (61.34 in.) |
| Rear (Back) track | 1592 mm (62.68 in.) |
| Drag coefficient (Cd) | 0.32 |
| Minimum turning circle | 11.4 m (37.4 ft.) |
| Drivetrain Architecture | Rear wheel drive |
| Drive wheel | Rear wheel drive |
| Number of gears | 6 gears, manual transmission |
| Front suspension | Coil spring |
| Rear suspension | Coil spring |
| Front brakes | Ventilated discs |
| Rear brakes | Disc |
| Assisting systems | ABS (Anti-lock braking system) |
| Steering type | Steering rack and pinion |
| Power steering | Hydraulic Steering |
| Tires size | 245/45 R18 |
| Wheel rims size | 8J x 18 |
Powertrain & Engine Architecture
The heart of the 645Ci is the N62B44, a 4.4-liter naturally aspirated V8 engine. This engine is a significant departure from the inline-six engines traditionally associated with BMW. The N62 featured all-aluminum construction, double overhead camshafts (DOHC) with four valves per cylinder, and a sophisticated multi-port fuel injection system. The engine produced 333 horsepower at 6100 rpm and 331.9 lb-ft of torque at 3600 rpm. The 645Ci was initially offered with a six-speed manual transmission, but a six-speed automatic transmission was also available, and became the more common choice for buyers prioritizing comfort and ease of use. The automatic transmission featured adaptive shift programs designed to optimize performance or fuel efficiency based on driving conditions.
Driving Characteristics
The 645Ci offered a refined and engaging driving experience. While not as overtly sporty as some of its competitors, the V8 engine provided ample power for confident acceleration and effortless highway cruising. The 0-60 mph sprint took approximately 5.8 seconds. The automatic transmission, while smooth, could sometimes feel hesitant during quick downshifts. The suspension, tuned for comfort, provided a compliant ride, but body roll was noticeable during aggressive cornering. Compared to the later 650i, the 645Ci offered a slightly lighter feel and a more manageable power delivery, making it a more approachable grand tourer for some drivers. The manual transmission version offered a more direct connection to the engine and a more engaging driving experience, but was less common in the US market.
Equipment & Trim Levels
The 645Ci came standard with a generous array of features, including leather upholstery, power-adjustable seats with memory function, automatic climate control, a premium sound system, and xenon headlights. Optional extras included a sport package (adding sport seats, a sport suspension, and unique exterior trim), a navigation system, active steering, and a head-up display. Interior trim options included various wood veneers and aluminum accents. The convertible top was a fully automatic, multi-layer fabric design that could be raised or lowered in around 20 seconds.
Chassis & Braking
The E64 645Ci utilized a MacPherson strut front suspension and a multi-link rear suspension, providing a good balance of ride comfort and handling. The braking system consisted of ventilated disc brakes at all four corners, with ABS (Anti-lock Braking System) standard. The steering was a rack-and-pinion system with hydraulic power assistance. The car’s weight distribution was close to 50/50, contributing to its balanced handling characteristics.
Market Reception & Comparison
The 645Ci was generally well-received by automotive critics, who praised its luxurious interior, powerful engine, and comfortable ride. However, some critics noted the car’s relatively high price and its tendency towards body roll during aggressive cornering. Compared to the 650i, the 645Ci offered a more affordable entry point into the 6 Series range, but with slightly less power and prestige. Fuel economy was a concern for some, with combined fuel consumption averaging around 18.2 US mpg. Reliability was generally good, but some owners reported issues with the cooling system and electronic components.
Legacy
The BMW 645Ci remains a desirable grand tourer in the used car market. The N62 V8 engine, while known for some potential cooling system issues (often related to the water pump), is generally considered reliable if properly maintained. The car’s elegant styling and luxurious interior continue to appeal to enthusiasts. Values have remained relatively stable, with well-maintained examples commanding a premium. The 645Ci represents a significant chapter in BMW’s history, showcasing the brand’s commitment to blending performance, luxury, and open-air driving enjoyment.
