The Alpina B6 Cabrio (E64) 4.4 V8 S, produced between 2007 and 2010, represents a high-performance iteration of the BMW 6 Series Convertible, meticulously engineered by the independent German automaker Alpina. Positioned as the flagship convertible within Alpina’s lineup during its production run, the B6 Cabrio blended luxurious open-top motoring with exhilarating performance. It was based on the E64 6-Series platform, benefitting from Alpina’s signature enhancements to the engine, suspension, and interior. This model aimed to deliver a more refined and powerful experience than the standard BMW 6 Series convertibles, appealing to drivers seeking exclusivity and a heightened level of performance.
Technical Specifications
| Brand | Alpina |
| Model | B6 |
| Generation | B6 Cabrio (E64) |
| Type (Engine) | 4.4 V8 S (530 Hp) |
| Start of production | 2007 |
| End of production | 2010 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Cabriolet |
| Seats | 4 |
| Doors | 2 |
| Fuel consumption (economy) – urban | 22.6 l/100 km (10.4 US mpg, 12.5 UK mpg, 4.4 km/l) |
| Fuel consumption (economy) – extra urban | 9.3 l/100 km (25.3 US mpg, 30.4 UK mpg, 10.8 km/l) |
| Fuel consumption (economy) – combined | 18.9 l/100 km (12.4 US mpg, 14.9 UK mpg, 5.3 km/l) |
| Fuel Type | Petrol (Gasoline) |
| Acceleration 0 – 100 km/h | 4.8 sec |
| Acceleration 0 – 62 mph | 4.8 sec |
| Acceleration 0 – 60 mph | 4.6 sec |
| Maximum speed | 313 km/h (194.49 mph) |
| Emission standard | Euro 4 |
| Weight-to-power ratio | 3.6 kg/Hp, 274.6 Hp/tonne |
| Weight-to-torque ratio | 2.7 kg/Nm, 375.6 Nm/tonne |
| Power | 530 Hp @ 5500 rpm |
| Power per litre | 120.5 Hp/l |
| Torque | 725 Nm @ 4750 rpm (534.73 lb.-ft. @ 4750 rpm) |
| Engine layout | Front, Longitudinal |
| 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 | 9:1 |
| Number of valves per cylinder | 4 |
| Fuel injection system | Multi-port manifold injection |
| Engine aspiration | Supercharger, Intercooler |
| Valvetrain | DOHC |
| Kerb Weight | 1930 kg (4254.92 lbs.) |
| Max. weight | 2190 kg (4828.12 lbs.) |
| Max load | 260 kg (573.2 lbs.) |
| Trunk (boot) space – maximum | 450 l (15.89 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 | 1371 mm (53.98 in.) |
| Wheelbase | 2780 mm (109.45 in.) |
| Front track | 1558 mm (61.34 in.) |
| Rear (Back) track | 1598 mm (62.91 in.) |
| 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 | 6 gears, automatic transmission |
| Front suspension | Independent, type McPherson with coil spring and anti-roll bar |
| Rear suspension | Independent multi-link suspension, Transverse stabilizer |
| Front brakes | Ventilated discs |
| Rear brakes | Ventilated discs |
| Assisting systems | ABS (Anti-lock braking system) |
| Steering type | Steering rack and pinion |
| Power steering | Hydraulic Steering |
| Tires size | Front wheel tires: 255/35 R20 Rear wheel tires: 285/30 R20 |
Powertrain & Engine Architecture
At the heart of the B6 Cabrio 4.4 V8 S lies Alpina’s heavily modified version of the BMW N62 V8 engine. Displacing 4.4 liters (4398 cc), this engine featured a supercharger, adding significant boost to the naturally aspirated BMW unit. The addition of an intercooler further enhanced performance by cooling the intake air. Alpina engineers also refined the engine management system, cylinder heads, and pistons to handle the increased power output of 530 horsepower at 5500 rpm and 725 Nm (534.73 lb-ft) of torque at 4750 rpm. The engine utilized multi-port fuel injection and a double overhead camshaft (DOHC) valvetrain with four valves per cylinder. Power was delivered to the rear wheels through a six-speed automatic transmission, specifically tuned by Alpina for smooth and responsive shifts. This transmission differed from the standard BMW automatic in its shift programming and torque converter lockup behavior, optimized for both performance and comfort.
Driving Characteristics
The B6 Cabrio 4.4 V8 S offered a distinctly different driving experience compared to the standard 6 Series convertibles, and even to other variants like the 650i. The supercharged V8 provided immediate and substantial power, resulting in a 0-60 mph time of approximately 4.6 seconds and a top speed of 313 km/h (194.49 mph). The Alpina-tuned automatic transmission contributed to this performance, offering quick and precise gear changes. While the standard 6 Series models prioritized a more relaxed grand touring experience, the B6 Cabrio emphasized performance and driver engagement. The suspension, while still comfortable, was firmer and more controlled, reducing body roll during cornering. The added weight of the supercharger and reinforced components did slightly impact fuel economy, but the performance gains were considered worthwhile by enthusiasts.
Equipment & Trim Levels
The B6 Cabrio was exceptionally well-equipped, reflecting its premium positioning. Standard features included leather upholstery, heated and ventilated front seats, a premium sound system, navigation system, and automatic climate control. Alpina-specific touches were evident throughout the interior, including unique badging, Alpina-branded steering wheel, and bespoke interior trim options. Customers could further personalize their B6 Cabrio with a range of optional extras, such as extended leather trim, active steering, and various driver assistance systems. Exterior features included Alpina’s signature aerodynamic body kit, including a front spoiler, rear diffuser, and unique alloy wheels.
Chassis & Braking
The B6 Cabrio retained the BMW 6 Series’ independent suspension setup, but with Alpina-specific modifications. The front suspension utilized a McPherson strut design with coil springs and an anti-roll bar, while the rear featured a multi-link setup with a transverse stabilizer. Alpina recalibrated the suspension geometry and damper settings to improve handling and reduce body roll. Braking duties were handled by ventilated disc brakes on all four wheels, coupled with an Anti-lock Braking System (ABS). The braking system was designed to provide ample stopping power and fade resistance, even under demanding driving conditions.
Market Reception & Comparison
The Alpina B6 Cabrio 4.4 V8 S was generally well-received by automotive critics, who praised its exceptional performance, luxurious interior, and exclusivity. Compared to the standard BMW 650i Convertible, the B6 offered a significant increase in power and a more focused driving experience. However, it came at a higher price point. Fuel economy was a common criticism, given the engine’s large displacement and supercharging. Reliability was generally good, benefiting from Alpina’s meticulous engineering and quality control.
Legacy
The Alpina B6 Cabrio (E64) 4.4 V8 S remains a sought-after vehicle among collectors and enthusiasts. The combination of a powerful supercharged V8 engine, luxurious interior, and exclusivity has ensured its enduring appeal. While maintenance costs can be higher than those of a standard BMW 6 Series, the B6 Cabrio offers a unique and rewarding driving experience. Well-maintained examples command premium prices in the used car market, reflecting their rarity and desirability. The powertrain, while complex, has proven relatively durable when properly serviced, making it a viable option for those seeking a high-performance luxury convertible.
