The BMW 4 Series Convertible (F33), specifically the 435d xDrive Steptronic variant produced from 2017 to 2020, represents a mid-cycle refresh (LCI – Life Cycle Impulse) of the F33 generation. Positioned as a premium offering within the 4 Series lineup, this model combined a potent diesel engine with BMW’s xDrive all-wheel-drive system and the Steptronic automatic transmission. It aimed to deliver a blend of performance, efficiency, and open-air driving enjoyment, appealing to buyers seeking a sophisticated grand tourer. The F33 generation itself was the convertible counterpart to the F32 4 Series Coupe, replacing the previous 3 Series Convertible (E93) and establishing a distinct identity for the 4 Series as a more style-focused and dynamically oriented vehicle.
Technical Specifications
| Brand | BMW |
| Model | 4 Series |
| Generation | 4 Series Convertible (F33, facelift 2017) |
| Type (Engine) | 435d (313 Hp) xDrive Steptronic |
| Start of production | 2017 |
| End of production | 2020 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Cabriolet |
| Seats | 4 |
| Doors | 2 |
| Fuel consumption (urban) | 6.8-7.0 l/100 km (34.6 – 33.6 US mpg, 41.5 – 40.4 UK mpg, 14.7 – 14.3 km/l) |
| Fuel consumption (extra urban) | 5.2-5.3 l/100 km (45.2 – 44.4 US mpg, 54.3 – 53.3 UK mpg, 19.2 – 18.9 km/l) |
| Fuel consumption (combined) | 5.7-5.9 l/100 km (41.3 – 39.9 US mpg, 49.6 – 47.9 UK mpg, 17.5 – 16.9 km/l) |
| CO2 emissions | 151-155 g/km |
| Fuel Type | Diesel |
| Acceleration 0 – 100 km/h | 5.7 sec |
| Acceleration 0 – 62 mph | 5.7 sec |
| Acceleration 0 – 60 mph | 5.4 sec |
| Maximum speed | 250 km/h (155.34 mph) |
| Emission standard | Euro 6 |
| Weight-to-power ratio | 5.9 kg/Hp, 169.2 Hp/tonne |
| Weight-to-torque ratio | 2.9 kg/Nm, 340.5 Nm/tonne |
| Power | 313 Hp @ 4400 rpm |
| Torque | 630 Nm @ 1500-2500 rpm (464.66 lb.-ft. @ 1500-2500 rpm) |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | N57D30B |
| 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 | 7.2 l (7.61 US qt | 6.34 UK qt) |
| Kerb Weight | 1850 kg (4078.55 lbs.) |
| Max. weight | 2290 kg (5048.59 lbs.) |
| Max load | 440 kg (970.03 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%) | 1800 kg (3968.32 lbs.) |
| Permitted trailer load without brakes | 750 kg (1653.47 lbs.) |
| Permitted towbar download | 75 kg (165.35 lbs.) |
| Length | 4640 mm (182.68 in.) |
| Width | 1825 mm (71.85 in.) |
| Height | 1399 mm (55.08 in.) |
| Wheelbase | 2810 mm (110.63 in.) |
| Front track | 1543 mm (60.75 in.) |
| Rear (Back) track | 1593 mm (62.72 in.) |
| Ride height (ground clearance) | 145 mm (5.71 in.) |
| Drag coefficient (Cd) | 0.30 |
| Minimum turning circle (turning diameter) | 11.8 m (38.71 ft.) |
| Drive wheel | All wheel drive (4×4) |
| Number of gears and type of gearbox | 8 gears, automatic transmission Steptronic |
| 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
The heart of the 435d xDrive Steptronic is BMW’s N57D30B inline-six diesel engine. This engine, a mainstay of BMW’s diesel offerings for many years, is renowned for its smooth operation and strong torque output. The ‘D30’ designation indicates a displacement of 3.0 liters (2993 cc). The N57 featured a common-rail direct injection system, delivering fuel at extremely high pressures for optimized combustion. A sophisticated twin-turbocharger setup – one low-inertia turbo for quick response and a larger turbo for peak power – contributed to the engine’s broad torque curve. The engine also incorporated variable valve timing (VANOS) and variable turbine geometry (VTG) on the turbochargers to further enhance efficiency and performance. The Steptronic 8-speed automatic transmission, a BMW staple, was paired with the engine. This transmission offered smooth, quick shifts and adaptive shift programs, optimizing for either fuel economy or performance. The xDrive all-wheel-drive system distributed power between the front and rear axles as needed, enhancing traction and stability, particularly in adverse weather conditions.
Driving Characteristics
The 435d xDrive Steptronic offered a distinctly different driving experience compared to its gasoline-powered siblings, such as the 435i or 440i. While lacking the high-revving excitement of the petrol engines, the 435d excelled in providing effortless, muscular acceleration. The abundant 630 Nm (464.66 lb-ft) of torque, available from just 1500 rpm, meant strong pulling power in any gear. The 8-speed automatic transmission was well-matched to the engine’s characteristics, providing seamless gear changes and contributing to a relaxed cruising experience. Compared to a manual transmission equipped 4 Series, the automatic offered convenience but slightly diminished driver engagement. The xDrive system provided confident handling and stability, particularly on slippery surfaces, making it a capable all-weather performer. The weight distribution, typical of BMW’s longitudinal engine layout, contributed to balanced handling characteristics.
Equipment & Trim Levels
The 435d xDrive Steptronic typically came well-equipped as standard. Features included leather upholstery, power-adjustable seats with memory function, a premium sound system, automatic climate control, and BMW’s iDrive infotainment system with a central display screen. Optional extras were plentiful, allowing buyers to personalize their vehicles. These included features like adaptive LED headlights, a head-up display, a parking assist system, a Harman Kardon surround sound system, and various interior trim options. The convertible top was a fully automatic, retractable hardtop, offering good insulation and security when closed. Trim levels beyond the standard 435d xDrive Steptronic were often defined by option packages, such as the Luxury Line, Sport Line, or M Sport package, which added cosmetic and performance enhancements.
Chassis & Braking
The F33 4 Series Convertible utilized a sophisticated chassis design. The front suspension featured independent coil springs and struts, while the rear employed an independent multi-link suspension. This setup aimed to provide a balance between comfort and handling precision. The 435d, being a higher-spec model, typically featured larger stabilizer bars compared to lower-trim variants, further reducing body roll during cornering. Braking duties were handled by ventilated disc brakes on all four wheels, providing ample stopping power. The ABS (Anti-lock Braking System) and electronic stability control systems were standard, enhancing safety and control. The steering system was a rack-and-pinion setup with electric power assistance, offering precise and responsive steering feel.
Market Reception & Comparison
The 435d xDrive Steptronic was generally well-received by automotive critics. It was praised for its strong performance, refined ride quality, and fuel efficiency. The diesel engine’s torque output was a particular highlight, making it a capable long-distance cruiser. Compared to the gasoline-powered 4 Series models, the 435d offered superior fuel economy and a more relaxed driving experience. However, some critics noted that the diesel engine lacked the aural excitement of the petrol engines. Against competitors like the Audi A5 Cabriolet and Mercedes-Benz C-Class Cabriolet, the 435d offered a compelling combination of performance, luxury, and technology. Its xDrive all-wheel-drive system gave it an advantage in regions with inclement weather.
Legacy
The N57 engine family, including the N57D30B found in the 435d, has proven to be remarkably durable and reliable. While diesel engines can be susceptible to issues with the diesel particulate filter (DPF) and turbocharger, the N57 has generally demonstrated good longevity with proper maintenance. On the used car market, the 435d xDrive Steptronic remains a desirable option for buyers seeking a refined and capable convertible. Its combination of performance, fuel efficiency, and all-weather capability continues to appeal to a wide range of drivers. However, potential buyers should be aware of the potential maintenance costs associated with a diesel engine, including DPF regeneration and injector servicing. Overall, the 435d xDrive Steptronic represents a well-engineered and enjoyable grand tourer that has stood the test of time.
