The Alpina B4 Cabrio (facelift 2017) S Edition 99 3.0, producing 452 horsepower, represents a high-performance iteration of the BMW 4 Series Convertible, meticulously refined by the independent German automaker Alpina. Production of this specific variant spanned from 2018 to 2019. Positioned as a limited-edition model, the S Edition 99 sat at the pinnacle of the B4 Cabrio range, offering a significant performance upgrade over the standard B4 and other variants. It was built upon the F33 generation 4 Series platform, benefitting from the 2017 facelift which included styling revisions and updated technology. The “99” designation signified a limited production run, enhancing its exclusivity and collectibility.
Technical Specifications
| Brand | Alpina |
| Model | B4 |
| Generation | B4 Cabrio (facelift 2017) |
| Type | S Edition 99 3.0 (452 Hp) Switch-Tronic |
| Start of production | 2018 |
| End of production | 2019 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Cabriolet |
| Seats | 4 |
| Doors | 2 |
| Fuel consumption (urban) | 12.1 l/100 km (19.4 US mpg, 23.3 UK mpg, 8.3 km/l) |
| Fuel consumption (extra urban) | 7.3 l/100 km (32.2 US mpg, 38.7 UK mpg, 13.7 km/l) |
| Fuel consumption (combined) | 9.1 l/100 km (25.8 US mpg, 31 UK mpg, 11 km/l) |
| CO2 emissions | 207 g/km |
| Fuel Type | Petrol (Gasoline) |
| Acceleration 0 – 100 km/h | 4.3 sec |
| Acceleration 0 – 62 mph | 4.3 sec |
| Acceleration 0 – 60 mph | 4.1 sec |
| Maximum speed | 304 km/h (188.9 mph) |
| Emission standard | Euro 6 d-TEMP |
| Weight-to-power ratio | 4.1 kg/Hp, 245.7 Hp/tonne |
| Weight-to-torque ratio | 2.7 kg/Nm, 369.6 Nm/tonne |
| Power | 452 Hp @ 5500-6250 rpm |
| Power per litre | 151.7 Hp/l |
| Torque | 680 Nm @ 3000-4500 rpm (501.54 lb.-ft. @ 3000-4500 rpm) |
| Engine layout | Front, Longitudinal |
| Engine displacement | 2979 cm3 (181.79 cu. in.) |
| Number of cylinders | 6 |
| Engine configuration | Inline |
| Cylinder Bore | 84 mm (3.31 in.) |
| Piston Stroke | 89.6 mm (3.53 in.) |
| Compression ratio | 10.2:1 |
| Number of valves per cylinder | 4 |
| Fuel injection system | Direct injection |
| Engine aspiration | BiTurbo, Intercooler |
| Kerb Weight | 1840 kg (4056.51 lbs.) |
| Max. weight | 2300 kg (5070.63 lbs.) |
| Max load | 460 kg (1014.13 lbs.) |
| Trunk (boot) space – minimum | 220 l (7.77 cu. ft.) |
| Trunk (boot) space – maximum | 370 l (13.07 cu. ft.) |
| Fuel tank capacity | 60 l (15.85 US gal, 13.2 UK gal) |
| Permitted trailer load with brakes (12%) | 1700 kg (3747.86 lbs.) |
| Permitted trailer load without brakes | 750 kg (1653.47 lbs.) |
| Length | 4640 mm (182.68 in.) |
| Width | 1825 mm (71.85 in.) |
| Height | 1380 mm (54.33 in.) |
| Wheelbase | 2810 mm (110.63 in.) |
| Front track | 1552 mm (61.1 in.) |
| Rear (Back) track | 1576 mm (62.05 in.) |
| Drivetrain Architecture | Rear wheel drive |
| Drive wheel | Rear wheel drive |
| Number of gears and type of gearbox | 8 gears, automatic transmission Switch-Tronic |
| Front brakes | Ventilated discs |
| Rear brakes | Ventilated discs |
| Assisting systems | ABS (Anti-lock braking system) |
| Steering type | Steering rack and pinion |
| Power steering | Electric Steering |
| Tires size | 245/30 ZR20; 265/30 ZR20 |
| Wheel rims size | 8J x 20; 9J x 20 |
Powertrain & Engine Architecture
At the heart of the B4 S Edition 99 lies Alpina’s version of the BMW N55 engine. This 3.0-liter inline-six engine is extensively modified from the standard BMW unit. The key upgrades include twin turbochargers with larger compressors, a revised intercooler system for improved cooling efficiency, and a bespoke engine management system calibrated specifically for Alpina. The engine utilizes direct fuel injection and double-VANOS variable valve timing, contributing to its responsive power delivery. The engine code is closely related to BMW’s N55, but with significant Alpina-specific components and tuning. The Switch-Tronic 8-speed automatic transmission, based on the ZF 8HP series, is also uniquely calibrated by Alpina. This transmission features a faster shift response and optimized gear ratios for performance, along with Alpina’s signature “Sport+” mode for more aggressive shifting.
Driving Characteristics
The B4 S Edition 99 delivers a distinctly refined yet potent driving experience. The 452 hp and 680 Nm (501.54 lb-ft) of torque provide effortless acceleration, with a 0-60 mph time of around 4.1 seconds. The Switch-Tronic transmission contributes to smooth and quick gear changes, enhancing both comfort and performance. Compared to the standard 4 Series Cabriolet or even the standard B4 Cabrio, the S Edition 99 offers a more immediate throttle response and a more engaging driving feel. While not as raw or track-focused as some dedicated sports cars, it strikes a compelling balance between grand touring comfort and spirited performance. The rear-wheel-drive configuration provides a traditional sports car feel, although traction control is essential to manage the power effectively.
Equipment & Trim Levels
The S Edition 99 was exceptionally well-equipped. Standard features included Alpina-specific exterior styling cues such as unique front and rear bumpers, aerodynamic side skirts, and a rear spoiler. Inside, the cabin featured Alpina sports seats upholstered in premium leather, an Alpina steering wheel, and unique interior trim elements. Additional standard equipment included a premium sound system, navigation, and a comprehensive suite of driver-assistance systems. Optional extras included a panoramic sunroof, upgraded interior trim materials, and bespoke paint options. The interior trim was generally more luxurious than the standard BMW 4 Series, with a focus on comfort and craftsmanship.
Chassis & Braking
The B4 S Edition 99 benefits from a revised suspension setup compared to the standard 4 Series. Alpina utilizes specifically tuned springs and dampers to provide a comfortable ride while maintaining excellent body control. The suspension geometry is also optimized for performance. Braking duties are handled by high-performance ventilated disc brakes on all four wheels, providing ample stopping power. The ABS system is calibrated to work effectively with the car’s performance capabilities. While the S Edition 99 doesn’t feature carbon-ceramic brakes, the standard braking system is more than adequate for most driving situations.
Market Reception & Comparison
The Alpina B4 S Edition 99 was generally well-received by automotive critics. Reviewers praised its blend of performance, luxury, and exclusivity. Compared to the standard BMW 4 Series Cabriolet, the Alpina offered a significant performance upgrade and a more refined driving experience. Compared to other high-performance convertibles in its class, such as the Porsche 911 Cabriolet, the B4 S Edition 99 offered a compelling value proposition, providing similar levels of performance at a lower price point. Fuel economy, while not a primary focus, was respectable for a high-performance vehicle, averaging around 25.8 US mpg in combined driving. Reliability was generally good, benefiting from Alpina’s meticulous engineering and quality control.
Legacy
The Alpina B4 S Edition 99 remains a desirable and collectible vehicle in the used car market. Its limited production run and unique specifications contribute to its enduring appeal. The N55 engine, while not the newest powerplant, is known for its durability and tunability. Regular maintenance, including oil changes and timely replacement of wear items, is crucial to ensure the long-term reliability of the powertrain. The Switch-Tronic transmission is also generally reliable, but requires proper fluid changes to maintain optimal performance. Today, the B4 S Edition 99 represents a unique and rewarding ownership experience for enthusiasts seeking a high-performance, luxurious, and exclusive convertible.
