The BMW 4 Series Convertible (F33), specifically the 420d variant produced from 2017 to 2020 following the facelift, represents a compelling blend of sporty aesthetics, diesel efficiency, and open-air driving enjoyment. Positioned as a mid-range offering within the 4 Series Convertible lineup, the 420d aimed to provide a more economical alternative to the higher-performance gasoline models, while still delivering a premium driving experience. This generation of the 4 Series Convertible, built on the F33 chassis, continued BMW’s tradition of offering a luxurious and engaging convertible experience, appealing to buyers seeking style and practicality in equal measure.
Technical Specifications
| Brand | BMW |
| Model | 4 Series |
| Generation | 4 Series Convertible (F33, facelift 2017) |
| Type (Engine) | 420d (190 Hp) |
| Start of production | 2017 |
| End of production | 2020 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Cabriolet |
| Seats | 4 |
| Doors | 2 |
| Fuel consumption (urban) | 5.7-6.1 l/100 km (41.3 – 38.6 US mpg, 49.6 – 46.3 UK mpg, 17.5 – 16.4 km/l) |
| Fuel consumption (extra urban) | 4.3-4.5 l/100 km (54.7 – 52.3 US mpg, 65.7 – 62.8 UK mpg, 23.3 – 22.2 km/l) |
| Fuel consumption (combined) | 4.8-5.1 l/100 km (49 – 46.1 US mpg, 58.9 – 55.4 UK mpg, 20.8 – 19.6 km/l) |
| CO2 emissions | 127-134 g/km |
| Fuel Type | Diesel |
| Acceleration 0 – 100 km/h | 8.1 sec |
| Acceleration 0 – 62 mph | 8.1 sec |
| Acceleration 0 – 60 mph | 7.7 sec |
| Maximum speed | 235 km/h (146.02 mph) |
| Emission standard | Euro 6 |
| Weight-to-power ratio | 8.9 kg/Hp, 111.8 Hp/tonne |
| Weight-to-torque ratio | 4.3 kg/Nm, 235.3 Nm/tonne |
| Power | 190 Hp @ 4000 rpm |
| Torque | 400 Nm @ 1750-2500 rpm (295.02 lb.-ft. @ 1750-2500 rpm) |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | B47D20A |
| Engine displacement | 1995 cm3 (121.74 cu. in.) |
| Number of cylinders | 4 |
| 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 | Direct injection |
| Engine aspiration | Twin-power turbo, Intercooler |
| Engine oil capacity | 5 l (5.28 US qt | 4.4 UK qt) |
| Coolant | 7 l (7.4 US qt | 6.16 UK qt) |
| Kerb Weight | 1700 kg (3747.86 lbs.) |
| Max. weight | 2170 kg (4784.03 lbs.) |
| Max load | 470 kg (1036.17 lbs.) |
| Trunk (boot) space – minimum | 370 l (13.07 cu. ft.) |
| Fuel tank capacity | 57 l (15.06 US gal | 12.54 UK gal) |
| Permitted trailer load with brakes (12%) | 1600 kg (3527.4 lbs.) |
| Permitted trailer load without brakes | 745 kg (1642.44 lbs.) |
| Permitted towbar download | 75 kg (165.35 lbs.) |
| Length | 4640 mm (182.68 in.) |
| Width | 1825 mm (71.85 in.) |
| Height | 1384 mm (54.49 in.) |
| Wheelbase | 2810 mm (110.63 in.) |
| Front track | 1544 mm (60.79 in.) |
| Rear (Back) track | 1593 mm (62.72 in.) |
| Ride height (ground clearance) | 130 mm (5.12 in.) |
| Drag coefficient (Cd) | 0.28 |
| Minimum turning circle (turning diameter) | 11.3 m (37.07 ft.) |
| 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, manual transmission |
| Front suspension | Independent coil spring |
| 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 | 225/50 R17; 225/45 R18; 255/40 R18; 225/40 R19; 255/35 R19 |
| Wheel rims size | 7.5J x 17; 8J x 18; 8.5J x 18; 8J x 19; 8.5J x 19 |
Powertrain & Engine Architecture
At the heart of the 420d Convertible lies the BMW B47D20A, a 2.0-liter inline-four cylinder diesel engine. This engine is a member of BMW’s modular engine family, known for its efficiency and refinement. The B47 utilizes a sophisticated common-rail direct fuel injection system, delivering fuel at extremely high pressures for optimized combustion. A twin-scroll turbocharger, coupled with an intercooler, provides a significant boost in power and torque. The engine boasts 190 horsepower at 4,000 rpm and a substantial 400 Nm (295 lb-ft) of torque available from a low 1,750 to 2,500 rpm. This broad torque curve contributes to strong acceleration and effortless cruising. The 420d was typically paired with a 6-speed manual transmission, although an 8-speed automatic transmission was also available as an option. The automatic transmission offered smoother shifts and enhanced convenience, particularly in urban driving conditions.
Driving Characteristics
The 420d Convertible, with its 190 hp and ample torque, offered a balanced driving experience. While not as overtly sporty as the gasoline-powered 430i or 440i models, the 420d provided sufficient power for confident overtaking and enjoyable cruising. The diesel engine’s low-end torque made it particularly well-suited for everyday driving, offering strong pull from a standstill. The 0-60 mph sprint took approximately 7.7 seconds, and the car could reach a top speed of 146 mph. The manual transmission provided a more engaging driving experience, allowing for greater control over gear selection, while the optional automatic transmission prioritized comfort and ease of use. The rear-wheel-drive configuration contributed to the car’s balanced handling characteristics, although it required careful throttle control in slippery conditions.
Equipment & Trim Levels
The 420d Convertible typically came standard with a generous array of features, including leather upholstery, automatic climate control, a BMW iDrive infotainment system with a central display screen, and a power-operated soft top. Optional extras included features such as navigation, premium sound systems (Harman Kardon), heated seats, parking sensors, and advanced driver-assistance systems like lane departure warning and adaptive cruise control. Trim levels varied depending on the market, but generally offered packages that bundled together popular options for added convenience and luxury. Interior color schemes and trim materials could also be customized to suit individual preferences.
Chassis & Braking
The F33 4 Series Convertible featured a sophisticated chassis design aimed at maximizing rigidity and handling performance. The suspension system consisted of independent coil springs at the front and an independent multi-link suspension at the rear. This setup provided a comfortable ride while maintaining good control and stability. Braking duties were handled by ventilated disc brakes on all four wheels, providing ample stopping power. Anti-lock Braking System (ABS) was standard, enhancing safety and control during emergency braking situations. The car’s weight distribution was carefully optimized to contribute to its balanced handling characteristics.
Market Reception & Comparison
The 420d Convertible was generally well-received by automotive critics, who praised its fuel efficiency, comfortable ride, and stylish design. It was often seen as a sensible alternative to the more expensive and less economical gasoline models. Compared to the 430i, the 420d offered significantly better fuel economy, but lacked the same level of outright performance. Against the 440i, the performance gap was even more pronounced. However, the 420d’s lower running costs and strong torque made it an attractive option for drivers who prioritized practicality and efficiency. Reliability reports generally indicated that the B47 engine was a robust and dependable unit, although some owners reported issues with the diesel particulate filter (DPF) system, particularly on vehicles used primarily for short trips.
Legacy
The BMW 420d Convertible (F33) remains a popular choice in the used car market, offering a compelling combination of style, comfort, and efficiency. The B47 engine has proven to be relatively reliable, although regular maintenance and adherence to BMW’s recommended service intervals are crucial for long-term durability. The car’s timeless design and engaging driving experience continue to appeal to buyers seeking a premium open-top experience. As with any used vehicle, prospective buyers should carefully inspect the car’s history and condition before making a purchase, paying particular attention to the condition of the soft top, the DPF system, and the overall mechanical health of the engine and transmission.
