The BMW 4 Series Convertible (G23) 430d, produced from 2021 to January 2024, represents a compelling blend of performance, efficiency, and open-air driving enjoyment within the broader G23 generation. Positioned as a mid-range offering in the 4 Series Convertible lineup, the 430d distinguishes itself through its potent diesel engine, mild-hybrid technology, and refined driving experience. This variant caters to drivers seeking a balance between spirited performance and respectable fuel economy, making it a popular choice in European markets where diesel engines remain prevalent. The G23 chassis, sharing its underpinnings with the 3 Series (G20), provides a solid foundation for the convertible’s dynamic capabilities.
Technical Specifications
| Brand | BMW |
| Model | 4 Series |
| Generation | 4 Series Convertible (G23) |
| Type (Engine) | 430d (286 Hp) Mild Hybrid Steptronic |
| Start of production | 2021 |
| End of production | January, 2024 |
| Powertrain Architecture | MHEV (Mild Hybrid Electric Vehicle) |
| Body type | Cabriolet |
| Seats | 4 |
| Doors | 2 |
| Combined fuel consumption (WLTP) | 5.3-6 l/100 km (44.4 – 39.2 US mpg, 53.3 – 47.1 UK mpg, 18.9 – 16.7 km/l) |
| CO2 emissions (WLTP) | 139-156 g/km |
| Fuel Type | Diesel |
| Acceleration 0 – 100 km/h | 5.8 sec |
| Acceleration 0 – 62 mph | 5.8 sec |
| Acceleration 0 – 60 mph | 5.5 sec |
| Maximum speed | 250 km/h (155.34 mph) |
| Emission standard | Euro 6d |
| Weight-to-power ratio | 6.6 kg/Hp, 152.1 Hp/tonne |
| Weight-to-torque ratio | 2.9 kg/Nm, 345.7 Nm/tonne |
| Gross battery capacity | 0.4 kWh |
| Battery voltage | 48 V |
| Battery technology | Lithium-ion (Li-Ion) |
| Battery location | Under the front hood |
| Electric motor power | 11 Hp |
| Electric motor Torque | 25 Nm (18.44 lb.-ft.) |
| Electric motor location | Front, Longitudinal |
| Power | 286 Hp @ 4000 rpm |
| Torque | 650 Nm @ 1500-2500 rpm (479.42 lb.-ft. @ 1500-2500 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 |
| Valvetrain | DOHC |
| Engine oil capacity | 7 l (7.4 US qt | 6.16 UK qt) |
| Coolant | 7.7 l (8.14 US qt | 6.78 UK qt) |
| Kerb Weight | 1880 kg (4144.69 lbs.) |
| Max. weight | 2380 kg (5247 lbs.) |
| Max load | 500 kg (1102.31 lbs.) |
| Trunk (boot) space – minimum | 300 l (10.59 cu. ft.) |
| Trunk (boot) space – maximum | 385 l (13.6 cu. ft.) |
| Fuel tank capacity | 59 l (15.59 US gal | 12.98 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 | 4768 mm (187.72 in.) |
| Width | 1852 mm (72.91 in.) |
| Height | 1384 mm (54.49 in.) |
| Wheelbase | 2851 mm (112.24 in.) |
| Front track | 1573 mm (61.93 in.) |
| Rear (Back) track | 1612 mm (63.46 in.) |
| Ride height (ground clearance) | 124 mm (4.88 in.) |
| Drag coefficient (Cd) | 0.28 |
| Minimum turning circle (turning diameter) | 11.4 m (37.4 ft.) |
| Drive wheel | Rear wheel drive |
| Number of gears and type of gearbox | 8 gears, automatic transmission Steptronic |
| Front suspension | Spring Strut, Transverse stabilizer |
| Rear suspension | Independent multi-link spring suspension with stabilizer |
| 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 |
| Wheel rims size | 7.5J x 17 |
Powertrain & Engine Architecture
At the heart of the 430d Convertible lies BMW’s B57D30B 3.0-liter inline-six diesel engine. This engine is a member of the modular BMW engine family, known for its robust construction and sophisticated technology. The B57 features a common-rail direct injection system, delivering fuel at extremely high pressures for optimized combustion. A twin-scroll turbocharger, coupled with an intercooler, enhances power output and responsiveness. The engine also incorporates variable valve timing (VANOS) and Double-VANOS technology for improved efficiency and reduced emissions. The mild-hybrid system, utilizing a 48V lithium-ion battery and an integrated starter generator, provides a power boost during acceleration and enables smoother start-stop operation. The Steptronic 8-speed automatic transmission is standard, offering quick and precise gear changes. This transmission is programmed for both efficiency and performance, adapting to the driver’s style and road conditions.
Driving Characteristics
The 430d Convertible delivers a refined and capable driving experience. While not as overtly sporty as the gasoline-powered 440i, the 430d offers ample torque – 650 Nm (479 lb-ft) – available from a low 1500 rpm. This provides strong acceleration in everyday driving situations and effortless overtaking. The 0-60 mph sprint takes approximately 5.5 seconds. The Steptronic transmission contributes to smooth power delivery, and the mild-hybrid system provides a noticeable boost during acceleration. The rear-wheel-drive configuration enhances handling balance, although it can be less forgiving in slippery conditions compared to all-wheel-drive variants. The convertible top, a fabric soft top, adds weight compared to the coupe, but the chassis is well-tuned to minimize body roll and maintain composure in corners.
Equipment & Trim Levels
The 430d Convertible typically came well-equipped as standard. Features included BMW’s iDrive infotainment system with a touchscreen display, navigation, Apple CarPlay and Android Auto compatibility, leather upholstery, automatic climate control, and a premium sound system. Optional extras included heated seats, a head-up display, adaptive cruise control, parking assist, and various cosmetic enhancements. Trim levels varied by market, but generally offered options for upgraded interior materials, exterior styling packages, and advanced driver-assistance systems. The convertible-specific features included wind deflector and neck warmers for enhanced open-top comfort.
Chassis & Braking
The G23 4 Series Convertible utilizes a sophisticated chassis design. The front suspension employs a spring strut setup with a transverse stabilizer, while the rear features an independent multi-link suspension, also with a stabilizer bar. This configuration provides a good balance between comfort and handling. The braking system consists of ventilated discs on all four wheels, providing ample stopping power. Anti-lock braking system (ABS) and electronic stability control (ESC) are standard safety features. The steering is an electric power-assisted rack-and-pinion system, offering precise and responsive control.
Market Reception & Comparison
The 430d Convertible was generally well-received by automotive critics. It was praised for its refined engine, comfortable ride, and stylish design. However, some reviewers noted that the diesel engine lacked the aural excitement of the gasoline alternatives. Compared to the 440i, the 430d offered superior fuel economy – typically around 5.3-6 l/100 km (44.4-39.2 mpg) – but slightly less outright performance. Against other diesel-powered convertibles in its class, the 430d stood out for its blend of luxury, performance, and technology. Its reliability has been generally good, with the B57 engine proving to be a durable and long-lasting unit.
Legacy
The BMW 4 Series Convertible (G23) 430d represents a significant step forward in diesel-powered convertible technology. The B57 engine, combined with the mild-hybrid system and Steptronic transmission, delivers a compelling driving experience. On the used car market, these models hold their value reasonably well, particularly those with low mileage and a comprehensive service history. The 430d’s blend of performance, efficiency, and luxury continues to appeal to drivers seeking a refined and versatile open-top experience. The powertrain is known for its longevity, making it a potentially reliable choice for buyers seeking a well-engineered and enjoyable convertible.
