The BMW 4 Series Convertible (G23) received a Life Cycle Impulse (LCI), or facelift, in March 2024. Among the updated variants, the M440d xDrive Steptronic represents a performance-oriented offering within the lineup. This model combines a 3.0-liter inline-six diesel engine with mild hybrid technology and BMW’s xDrive all-wheel-drive system, paired with an eight-speed Steptronic automatic transmission. Positioned as a premium trim, the M440d caters to drivers seeking a blend of performance, efficiency, and luxury in a convertible package. It builds upon the foundation of the G23 platform, which debuted in 2020, offering a refreshed design and updated technology.
Technical Specifications
| Brand | BMW |
| Model | 4 Series |
| Generation | 4 Series Convertible (G23 LCI, facelift 2024) |
| Type (Engine) | M440d (340 Hp) Mild Hybrid xDrive Steptronic |
| Start of production | March, 2024 |
| Powertrain Architecture | MHEV (Mild Hybrid Electric Vehicle) |
| Body type | Cabriolet |
| Seats | 4 |
| Doors | 2 |
| Combined fuel consumption (WLTP) | 6.4-6.9 l/100 km (36.8 – 34.1 US mpg, 44.1 – 40.9 UK mpg, 15.6 – 14.5 km/l) |
| CO2 emissions (WLTP) | 167-182 g/km |
| Fuel Type | Diesel |
| Acceleration 0 – 100 km/h | 5 sec |
| Acceleration 0 – 62 mph | 5 sec |
| Acceleration 0 – 60 mph | 4.8 sec |
| Maximum speed | 250 km/h (155.34 mph) – Electronically limited |
| Emission standard | Euro 6e |
| Weight-to-power ratio | 5.8 kg/Hp, 171.7 Hp/tonne |
| Weight-to-torque ratio | 2.8 kg/Nm, 353.5 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 | 340 Hp @ 4400 rpm |
| Torque | 700 Nm @ 1750-2250 rpm (516.29 lb.-ft. @ 1750-2250 rpm) |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | B57 |
| 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) |
| Kerb Weight | 1980 kg (4365.15 lbs.) |
| Max. weight | 2465 kg (5434.39 lbs.) |
| Max load | 485 kg (1069.24 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 | 4770 mm (187.8 in.) |
| Width | 1852 mm (72.91 in.) |
| Width including mirrors | 2081 mm (81.93 in.) |
| Height | 1394 mm (54.88 in.) |
| Wheelbase | 2851 mm (112.24 in.) |
| Front track | 1583 mm (62.32 in.) |
| Rear (Back) track | 1592 mm (62.68 in.) |
| Front overhang | 858 mm (33.78 in.) |
| Rear overhang | 1061 mm (41.77 in.) |
| Ride height (ground clearance) | 126 mm (4.96 in.) |
| Drag coefficient (Cd) | 0.28 |
| Minimum turning circle (turning diameter) | 12 m (39.37 ft.) |
| Drivetrain Architecture | ICE and electric motor drive all four wheels, operating in mixed mode. |
| Drive wheel | All wheel drive (4×4) |
| 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 | Front: 225/45 R18, Rear: 255/40 R18 |
| Wheel rims size | Front: 7.5J x 18, Rear: 8.5J x 18 |
Powertrain & Engine Architecture
The heart of the M440d is BMW’s B57 3.0-liter inline-six diesel engine. This engine benefits from a comprehensive update for the LCI model, incorporating the latest generation of common-rail direct injection technology and a two-stage turbocharging system. The first turbocharger provides rapid response at low engine speeds, while the second, larger turbocharger delivers increased power at higher RPMs. The engine produces 340 horsepower at 4400 rpm and a substantial 700 Nm (516 lb-ft) of torque between 1750 and 2250 rpm. The mild hybrid system, utilizing a 48V lithium-ion battery and an integrated starter generator, provides an additional 11 horsepower and 25 Nm (18 lb-ft) of torque, assisting during acceleration and enabling smoother start-stop operation. The eight-speed Steptronic automatic transmission is specifically tuned to complement the engine’s characteristics, offering quick and precise gear changes.
Driving Characteristics
The M440d xDrive delivers a refined yet potent driving experience. The combination of the powerful diesel engine, mild hybrid assistance, and all-wheel drive provides strong acceleration – achieving 0-60 mph in approximately 4.8 seconds. The xDrive system intelligently distributes torque between the front and rear axles, ensuring optimal traction and stability in various driving conditions. Compared to lower-powered 4 Series variants, such as the 420i, the M440d offers significantly more responsive acceleration and effortless cruising ability. While not as overtly sporty as the M4, the M440d provides a compelling balance of performance and comfort. The Steptronic transmission offers both automatic and manual shift modes, allowing drivers to tailor the driving experience to their preferences.
Equipment & Trim Levels
The M440d typically comes well-equipped as standard. Key features include BMW’s Live Cockpit Professional (digital instrument cluster and infotainment system), leather upholstery, heated front seats, automatic climate control, and a premium sound system. The LCI update brought enhancements to the interior design and infotainment system. Optional extras include adaptive suspension, upgraded leather trim, a head-up display, and various driver-assistance systems like lane keeping assist and adaptive cruise control. The convertible top is a fully automatic soft top, offering a quiet and comfortable cabin experience when raised.
Chassis & Braking
The G23 chassis is designed to provide a balance of agility and comfort. The front suspension utilizes a spring strut design with a transverse stabilizer, while the rear features an independent multi-link setup, also with a stabilizer bar. The M440d benefits from slightly stiffer spring rates and dampers compared to lower-powered models, enhancing handling precision. Braking is handled by ventilated discs on all four wheels, providing ample stopping power. The ABS system and electronic stability control further enhance safety and control.
Market Reception & Comparison
The M440d xDrive Convertible has been generally well-received by automotive critics. It’s praised for its strong performance, refined ride quality, and fuel efficiency for a vehicle of its class. Compared to the gasoline-powered 440i Convertible, the M440d offers superior torque and potentially better fuel economy, particularly for long-distance driving. However, the diesel engine may not appeal to all buyers. The M440d’s price point positions it as a premium offering within the 4 Series range, competing with other luxury convertibles from brands like Audi and Mercedes-Benz.
Legacy
The B57 engine family has proven to be remarkably reliable, and the mild hybrid integration is expected to further enhance its longevity. The G23 platform, while relatively new, has established a reputation for solid build quality. As the LCI models enter the used car market, the M440d is likely to hold its value well due to its desirable combination of performance, luxury, and efficiency. Proper maintenance, including regular servicing and adherence to BMW’s recommended maintenance schedule, will be crucial to ensuring the long-term reliability of this powertrain.
