The BMW 8 Series Convertible (G14) 840d xDrive Steptronic, produced from 2019 to 2020, represents a compelling blend of luxury, performance, and efficiency within the broader 8 Series (G14) convertible lineup. Positioned as a mid-range offering, it slotted between the entry-level 840i gasoline variant and the higher-performance M850i. This model aimed to provide a refined grand touring experience with the added benefit of diesel fuel economy, appealing to buyers prioritizing long-distance comfort and reduced running costs. The G14 generation marked the revival of the 8 Series nameplate after a nearly two-decade hiatus, and the 840d played a significant role in establishing the model’s presence in the luxury convertible market, particularly in Europe where diesel engines remained popular.
Technical Specifications
| Brand | BMW |
| Model | 8 Series |
| Generation | 8 Series Convertible (G14) |
| Type (Engine) | 840d (320 Hp) xDrive Steptronic |
| Start of production | 2019 |
| End of production | 2020 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Cabriolet |
| Seats | 4 |
| Doors | 2 |
| Fuel consumption (urban) | 7.3-7.4 l/100 km (32.2 – 31.8 US mpg, 38.7 – 38.2 UK mpg, 13.7 – 13.5 km/l) |
| Fuel consumption (extra urban) | 5.1-5.6 l/100 km (46.1 – 42 US mpg, 55.4 – 50.4 UK mpg, 19.6 – 17.9 km/l) |
| Fuel consumption (combined) | 5.9-6.3 l/100 km (39.9 – 37.3 US mpg, 47.9 – 44.8 UK mpg, 16.9 – 15.9 km/l) |
| CO2 emissions | 155-166 g/km |
| Fuel Type | Diesel |
| Acceleration 0 – 100 km/h | 5.2 sec |
| Acceleration 0 – 62 mph | 5.2 sec |
| Acceleration 0 – 60 mph | 4.9 sec |
| Maximum speed | 250 km/h (155.34 mph) |
| Emission standard | Euro 6d |
| Weight-to-power ratio | 6.1 kg/Hp, 163.7 Hp/tonne |
| Weight-to-torque ratio | 2.9 kg/Nm, 347.8 Nm/tonne |
| Power | 320 Hp @ 4400 rpm |
| Torque | 680 Nm @ 1750-2250 rpm (501.54 lb.-ft. @ 1750-2250 rpm) |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | B57D30B |
| Engine displacement | 2993 cm3 (182.64 cu. in.) |
| Number of cylinders | 6 |
| Engine configuration | Inline |
| Cylinder Bore | 84 mm (3.31 in.) |
| Piston Stroke | 90 mm (3.54 in.) |
| Compression ratio | 16.5:1 |
| Number of valves per cylinder | 4 |
| Fuel injection system | Diesel Commonrail |
| Engine aspiration | Twin-power turbo, Intercooler |
| Engine oil capacity | 6.5 l (6.87 US qt | 5.72 UK qt) |
| Coolant | 9.5 l (10.04 US qt | 8.36 UK qt) |
| Kerb Weight | 1955 kg (4310.04 lbs.) |
| Max. weight | 2485 kg (5478.49 lbs.) |
| Max load | 530 kg (1168.45 lbs.) |
| Trunk (boot) space – minimum | 350 l (12.36 cu. ft.) |
| Fuel tank capacity | 66 l (17.44 US gal | 14.52 UK gal) |
| Length | 4843 mm (190.67 in.) |
| Width | 1902 mm (74.88 in.) |
| Width including mirrors | 2137 mm (84.13 in.) |
| Height | 1339 mm (52.72 in.) |
| Wheelbase | 2822 mm (111.1 in.) |
| Front track | 1619 mm (63.74 in.) |
| Rear (Back) track | 1642 mm (64.65 in.) |
| Ride height (ground clearance) | 118 mm (4.65 in.) |
| Drag coefficient (Cd) | 0.30 |
| Minimum turning circle | 11.9 m (39.04 ft.) |
| Drive wheel | All wheel drive (4×4) |
| Number of gears and type of gearbox | 8 gears, automatic transmission Steptronic |
| Front suspension | Double wishbone |
| Rear suspension | Independent multi-link suspension |
| 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 | 245/45 R18 100Y; 275/40 R18 103Y |
| Wheel rims size | 8J x 18; 9J x 18 |
Powertrain & Engine Architecture
The heart of the 840d xDrive Steptronic is BMW’s B57D30B 3.0-liter inline-six diesel engine. This engine is a member of the modular B-series engine family, known for its robust construction and advanced technology. The B57 features a common-rail direct injection system operating at extremely high pressures (2,500 bar) for optimized fuel atomization and combustion efficiency. A sophisticated twin-turbocharger setup – employing a variable geometry turbocharger (VGT) and a conventional turbocharger – provides a broad torque curve and minimizes turbo lag. The engine also incorporates an intercooler to further enhance intake air density. The engine produces 320 horsepower at 4,400 rpm and a substantial 680 Nm (501.54 lb-ft) of torque between 1,750 and 2,250 rpm. This torque output is a key characteristic of the engine, providing effortless acceleration and strong in-gear performance. The engine is paired with BMW’s 8-speed Steptronic automatic transmission, known for its smooth and quick shifts. The Steptronic transmission offers both automatic and manual shift modes, allowing the driver to tailor the driving experience to their preferences. The xDrive all-wheel-drive system distributes power between the front and rear axles as needed, enhancing traction and stability in all weather conditions.
Driving Characteristics
The 840d xDrive Steptronic delivers a refined and comfortable driving experience. The abundant torque from the diesel engine provides strong acceleration from low speeds, making it ideal for everyday driving and effortless highway cruising. While not as overtly sporty as the 840i or M850i, the 840d offers more than adequate performance, with a 0-60 mph time of around 4.9 seconds. The 8-speed automatic transmission contributes to the smooth driving experience, providing seamless gear changes. The xDrive all-wheel-drive system enhances stability and traction, particularly in inclement weather. Compared to the 840i, the 840d offers superior fuel economy, making it a more practical choice for long-distance travel. However, it lacks the higher engine output and more aggressive exhaust note of the gasoline-powered models. The gear ratios are tuned for a balance of acceleration and fuel efficiency, with taller gears for relaxed cruising and shorter gears for quicker response.
Equipment & Trim Levels
The 840d xDrive Steptronic came well-equipped as standard, reflecting its positioning as a luxury convertible. Standard features typically included leather upholstery, power-adjustable seats with memory function, a premium sound system, a navigation system, and a comprehensive suite of driver-assistance features such as lane departure warning, forward collision warning, and automatic emergency braking. Optional extras included upgraded leather options, a head-up display, a Bowers & Wilkins Diamond surround sound system, and active roll stabilization. The interior design emphasized luxury and sophistication, with high-quality materials and a minimalist dashboard layout. The convertible top was a fully automatic soft top, offering a quiet and comfortable cabin experience when raised.
Chassis & Braking
The 8 Series Convertible (G14) utilizes a sophisticated chassis design to deliver a comfortable yet engaging driving experience. The front suspension features a double-wishbone setup, while the rear suspension employs an independent multi-link design. This configuration provides excellent ride quality and precise handling. The 840d xDrive Steptronic is equipped with ventilated disc brakes on all four wheels, providing ample stopping power. The braking system is further enhanced by ABS (Anti-lock Braking System) and electronic brake-force distribution. The steering system is an electric power steering system, offering precise and responsive steering feel. The car’s weight distribution is carefully optimized to enhance handling balance.
Market Reception & Comparison
The BMW 840d xDrive Steptronic was generally well-received by automotive critics. It was praised for its refined driving experience, strong performance, and excellent fuel economy. Critics noted that the diesel engine provided ample torque for effortless cruising, and the xDrive all-wheel-drive system enhanced stability and traction. Compared to the 840i, the 840d offered a more practical and economical option, particularly for drivers who frequently undertake long journeys. However, some critics found the diesel engine to be less engaging than the gasoline-powered alternatives. In terms of reliability, the B57 engine has proven to be a robust and durable unit, with relatively few reported issues.
Legacy
The BMW 840d xDrive Steptronic represents a compelling combination of luxury, performance, and efficiency. The B57 diesel engine has established a reputation for reliability and longevity, making these models attractive on the used car market. While diesel engines have faced increasing scrutiny in recent years, the 840d remains a desirable option for buyers seeking a refined and economical grand tourer. Its blend of comfort, performance, and technology ensures its continued appeal for years to come. The G14 8 Series, and the 840d variant specifically, helped re-establish the 8 Series as a flagship luxury offering for BMW.
