The BMW 4 Series Convertible (G23) M440i, produced from 2020 through January 2024, represents a compelling blend of performance and open-air driving enjoyment within the broader G23 generation. Positioned as a mid-to-high range trim, the M440i distinguishes itself through its potent inline-six engine, mild-hybrid technology, and sophisticated Steptronic automatic transmission. This variant aimed to deliver a more engaging driving experience than the base 430i models, while offering a more refined and technologically advanced package compared to earlier 4 Series convertibles.
Technical Specifications
| Brand | BMW |
| Model | 4 Series |
| Generation | 4 Series Convertible (G23) |
| Type (Engine) | M440i (382 Hp) Mild Hybrid Steptronic |
| Start of production | 2020 |
| End of production | January, 2024 |
| Powertrain Architecture | MHEV (Mild Hybrid Electric Vehicle) |
| Body type | Cabriolet |
| Seats | 4 |
| Doors | 2 |
| Fuel consumption (urban) | 10.2 l/100 km (23.1 US mpg) |
| Fuel consumption (extra urban) | 7.6 l/100 km (30.9 US mpg) |
| Fuel consumption (combined) | 9 l/100 km (26.1 US mpg) |
| Fuel Type | Petrol (Gasoline) |
| Acceleration 0 – 60 mph | 5 sec |
| Maximum speed | 210 km/h (130.49 mph) |
| Weight-to-power ratio | 5 kg/Hp |
| Weight-to-torque ratio | 3.8 kg/Nm |
| Gross battery capacity | 0.4 kWh |
| Battery voltage | 48 V |
| Battery technology | Lithium-ion (Li-Ion) |
| Electric motor power | 11 Hp |
| Electric motor Torque | 25 Nm (18.44 lb.-ft.) |
| Power | 382 Hp @ 5800-6500 rpm |
| Torque | 500 Nm @ 1800-5000 rpm (368.78 lb.-ft. @ 1800-5000 rpm) |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | B58B30O1 |
| Engine displacement | 2998 cm3 (182.95 cu. in.) |
| Number of cylinders | 6 |
| Engine configuration | Inline |
| Cylinder Bore | 82 mm (3.23 in.) |
| Piston Stroke | 94.6 mm (3.72 in.) |
| Compression ratio | 10.2:1 |
| Fuel injection system | Direct injection |
| Engine aspiration | Twin-power turbo, Intercooler |
| Valvetrain | Double-VANOS, VALVETRONIC |
| Engine oil capacity | 6.5 l (6.87 US qt | 5.72 UK qt) |
| Kerb Weight | 1892 kg (4171.15 lbs.) |
| Max. weight | 2300 kg (5070.63 lbs.) |
| Max load | 408 kg (899.49 lbs.) |
| Trunk (boot) space (min) | 300 l (10.59 cu. ft.) |
| Trunk (boot) space (max) | 385 l (13.6 cu. ft.) |
| Fuel tank capacity | 59 l (15.59 US gal | 12.98 UK gal) |
| Length | 4775 mm (187.99 in.) |
| Width | 1852 mm (72.91 in.) |
| Width including mirrors | 2081 mm (81.93 in.) |
| Height | 1387 mm (54.61 in.) |
| Wheelbase | 2851 mm (112.24 in.) |
| Front track | 1582 mm (62.28 in.) |
| Rear track | 1593 mm (62.72 in.) |
| Ride height (ground clearance) | 127 mm (5 in.) |
| Drag coefficient (Cd) | 0.28 |
| Minimum turning circle | 11.4 m (37.4 ft.) |
| Number of gears | 8 |
| Gearbox type | Automatic (Steptronic) |
Powertrain & Engine Architecture
At the heart of the M440i lies the BMW B58B30O1 3.0-liter inline-six engine. This engine is a cornerstone of BMW’s modern powertrain strategy, known for its smooth power delivery and responsiveness. The B58 utilizes direct fuel injection, a twin-scroll turbocharger, and BMW’s VALVETRONIC variable valve timing and lift system, along with Double-VANOS variable camshaft timing. These technologies work in concert to optimize combustion efficiency and maximize power output across the rev range. The mild-hybrid system, incorporating a 48V lithium-ion battery and an integrated starter generator, provides a power boost during acceleration and enables smoother start-stop operation, contributing to improved fuel economy. The engine is paired with BMW’s eight-speed Steptronic automatic transmission, offering both fully automatic operation and manual gear selection via steering wheel-mounted paddles. This transmission is characterized by its quick and precise shifts, enhancing the overall driving experience.
Driving Characteristics
The M440i Convertible delivers a refined yet engaging driving experience. The 382 horsepower and 368 lb-ft of torque provide ample power for spirited acceleration, achieving 0-60 mph in approximately 5 seconds. The Steptronic transmission is well-tuned to the engine’s characteristics, providing seamless gear changes in automatic mode and responsive control when shifting manually. Compared to the 430i Convertible, the M440i offers a noticeable increase in performance, particularly in mid-range acceleration. While not as overtly sporty as the M4 Convertible, the M440i strikes a balance between performance and comfort, making it a suitable choice for both daily driving and weekend excursions. The mild-hybrid system contributes to a smoother and more refined driving experience, particularly in urban environments.
Equipment & Trim Levels
The M440i Convertible came standard with a comprehensive array of features, including BMW’s iDrive infotainment system with a touchscreen display, navigation, Apple CarPlay and Android Auto compatibility, and a premium sound system. Interior appointments typically included leather upholstery, power-adjustable seats with memory function, and a sport steering wheel. Standard safety features included automatic emergency braking, lane departure warning, and adaptive cruise control. Optional extras included a head-up display, ventilated seats, a Harman Kardon sound system, and various cosmetic enhancements. The convertible top was a fully automatic soft top, available in several colors, and could be raised or lowered in approximately 18 seconds at speeds up to 31 mph.
Chassis & Braking
The G23 M440i Convertible features a chassis designed to balance handling precision with ride comfort. The front suspension utilizes a spring strut design with a transverse stabilizer, while the rear suspension employs an independent multi-link setup, also with a stabilizer bar. The braking system consists of ventilated discs on all four wheels, providing ample stopping power. The standard wheels were 18-inch alloy wheels, with 19-inch wheels available as an option. The steering system is an electric power-assisted rack-and-pinion setup, offering precise and responsive steering feel.
Market Reception & Comparison
The M440i Convertible was generally well-received by automotive critics, who praised its powerful engine, refined driving dynamics, and luxurious interior. Compared to the 430i Convertible, the M440i offered a significant performance upgrade, justifying its higher price tag for enthusiasts seeking a more engaging driving experience. Fuel economy figures were respectable for a performance convertible, averaging around 26.1 US mpg in combined driving. Reliability reports have been generally positive, with the B58 engine proving to be a robust and dependable unit. However, as with any complex modern vehicle, preventative maintenance is crucial to ensure long-term reliability.
Legacy
The BMW 4 Series Convertible (G23) M440i represents a high point in BMW’s convertible offerings, combining performance, luxury, and technology in a compelling package. The B58 engine has established itself as a benchmark for inline-six engines, and the mild-hybrid system foreshadowed BMW’s broader electrification strategy. On the used car market, the M440i Convertible holds its value well, attracting buyers who appreciate its blend of performance and refinement. With proper maintenance, these vehicles are expected to provide many years of enjoyable open-air motoring.
