Technical Specifications
| Brand | BMW |
| Model | 4 Series |
| Generation | 4 Series Convertible (G23) |
| Type (Engine) | 420i (184 Hp) Steptronic |
| Start of production | 2020 |
| End of production | January, 2024 |
| Powertrain Architecture | Internal Combustion engine |
| Body type | Cabriolet |
| Seats | 4 |
| Doors | 2 |
| Combined fuel consumption (WLTP) | 6.7-7.4 l/100 km (35.1 – 31.8 US mpg, 42.2 – 38.2 UK mpg, 14.9 – 13.5 km/l) |
| CO2 emissions (WLTP) | 152-169 g/km |
| Fuel consumption (economy) – urban (NEDC) | 7.1-7.4 l/100 km (33.1 – 31.8 US mpg, 39.8 – 38.2 UK mpg, 14.1 – 13.5 km/l) |
| Fuel consumption (economy) – extra urban (NEDC) | 4.9-5.4 l/100 km (48 – 43.6 US mpg, 57.6 – 52.3 UK mpg, 20.4 – 18.5 km/l) |
| Fuel consumption (economy) – combined (NEDC) | 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) |
| CO2 emissions (NEDC) | 131-140 g/km |
| Fuel Type | Petrol (Gasoline) |
| Acceleration 0 – 100 km/h | 8.2 sec |
| Acceleration 0 – 62 mph | 8.2 sec |
| Acceleration 0 – 60 mph | 7.8 sec |
| Maximum speed | 236 km/h (146.64 mph) |
| Emission standard | Euro 6d |
| Weight-to-power ratio | 9.2 kg/Hp, 108.9 Hp/tonne |
| Weight-to-torque ratio | 5.6 kg/Nm, 177.5 Nm/tonne |
| Power | 184 Hp @ 5000-6500 rpm |
| Power per litre | 92.1 Hp/l |
| Torque | 300 Nm @ 1350-4000 rpm (221.27 lb.-ft. @ 1350-4000 rpm) |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | B48B20A |
| Engine displacement | 1998 cm3 (121.93 cu. in.) |
| Number of cylinders | 4 |
| Engine configuration | Inline |
| Cylinder Bore | 82 mm (3.23 in.) |
| Piston Stroke | 94.6 mm (3.72 in.) |
| Compression ratio | 11:1 |
| Number of valves per cylinder | 4 |
| Fuel injection system | Direct injection |
| Engine aspiration | Twin-power turbo, Intercooler |
| Valvetrain | VALVETRONIC |
| Engine oil capacity | 5.25 l (5.55 US qt | 4.62 UK qt) |
| Coolant | 10 l (10.57 US qt | 8.8 UK qt) |
| Kerb Weight | 1690 kg (3725.81 lbs.) |
| Max. weight | 2185 kg (4817.1 lbs.) |
| Max load | 495 kg (1091.29 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%) | 1600 kg (3527.4 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.) |
| Width including mirrors | 2081 mm (81.93 in.) |
| Height | 1384 mm (54.49 in.) |
| Wheelbase | 2851 mm (112.24 in.) |
| Front track | 1575 mm (62.01 in.) |
| Rear (Back) track | 1611 mm (63.43 in.) |
| Front overhang | 858 mm (33.78 in.) |
| Rear overhang | 1059 mm (41.69 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.) |
| 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 | 8 gears, automatic transmission Steptronic |
| Front suspension | Double wishbone |
| 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 98Y XL |
| Wheel rims size | 7.5J x 17 |
The BMW 4 Series Convertible (G23) 420i Steptronic, launched in 2020, is part of the third generation of the 4 Series convertible, built on the 1HX0/A3 platform shared with the 3 Series. This generation marked a significant departure in styling with its prominent kidney grille, and the 420i served as the entry-level offering, providing a balance between BMW’s renowned driving dynamics and accessible luxury. It aimed to attract customers seeking a stylish, open-top experience without the higher price tag and performance focus of the more potent models. Production continued until January 2024, making it a relatively short-lived variant within the G23 lifecycle.
Powertrain & Engine Architecture
At the heart of the 420i lies BMW’s B48B20A 2.0-liter turbocharged inline-four cylinder engine. This engine is a cornerstone of BMW’s modern powertrain strategy, featuring direct fuel injection, a twin-scroll turbocharger, and BMW’s VALVETRONIC variable valve timing and lift system. VALVETRONIC allows for precise control of valve timing and lift, optimizing engine efficiency and responsiveness. The engine produces 184 horsepower at 5000-6500 rpm and 300 Nm (221 lb-ft) of torque between 1350 and 4000 rpm. This torque curve provides good low-end and mid-range grunt, making it suitable for everyday driving. The engine is longitudinally mounted, driving the rear wheels. Paired with the engine is BMW’s eight-speed Steptronic automatic transmission. This transmission is known for its smooth and quick shifts, and it contributes to both performance and fuel efficiency. The transmission features a torque converter and offers both automatic and manual shift modes.
Driving Characteristics
The 420i Steptronic delivers a comfortable and refined driving experience. While not as overtly sporty as the 430i or M440i, it provides ample power for everyday driving and enjoyable cruising. The eight-speed automatic transmission is well-tuned, offering smooth gear changes and contributing to a relaxed driving experience. The gear ratios are optimized for both fuel efficiency and responsiveness. Acceleration from 0 to 60 mph takes approximately 7.8 seconds, and the car has a top speed of 146.64 mph. Compared to the manual transmission versions of the 420i, the Steptronic offers greater convenience, particularly in urban environments. However, some driving enthusiasts may prefer the more engaging experience of a manual gearbox. The 420i’s suspension is tuned for comfort, providing a smooth ride over most road surfaces. The steering is precise and well-weighted, offering good feedback to the driver.
Equipment & Trim Levels
The 420i Convertible came standard with a comprehensive list of features, including BMW’s iDrive infotainment system with a 8.8-inch touchscreen display, navigation, Apple CarPlay and Android Auto compatibility, and a premium sound system. Standard interior features included leatherette upholstery, power-adjustable front seats, and automatic climate control. Exterior features included LED headlights, 17-inch alloy wheels, and a power-operated soft top. Optional extras included leather upholstery, heated seats, a head-up display, a Harman Kardon sound system, and various driver-assistance systems such as lane departure warning and adaptive cruise control. The trim levels offered allowed for customization, with options to upgrade interior materials and add additional features.
Chassis & Braking
The G23 420i Convertible utilizes a double-wishbone front suspension and an independent multi-link rear suspension. This suspension setup provides a good balance between comfort and handling. The car is equipped with ventilated disc brakes on all four wheels, providing ample stopping power. Anti-lock braking system (ABS) is standard, along with electronic stability control and traction control. The chassis is designed to provide rigidity, minimizing body roll and enhancing handling. The weight distribution is optimized for balanced handling, contributing to the car’s overall driving dynamics.
Market Reception & Comparison
The 420i Convertible was generally well-received by automotive critics. It was praised for its comfortable ride, refined interior, and fuel efficiency. However, some critics noted that the engine lacked the outright performance of the more powerful 430i and M440i models. Compared to the 430i, the 420i offered a more affordable entry point into the 4 Series Convertible range, but at the expense of performance. The 420i’s fuel economy was comparable to that of the 430i, but it offered slightly better fuel efficiency in real-world driving conditions. Reliability reports have been generally positive, with few major issues reported.
Legacy
The BMW 4 Series Convertible (G23) 420i Steptronic represents a compelling option for buyers seeking a stylish and comfortable open-top experience. The B48 engine and Steptronic transmission have proven to be reliable and durable, and the car is expected to hold its value well in the used car market. While it may not be the most performance-oriented variant of the 4 Series Convertible, it offers a balanced combination of luxury, comfort, and efficiency, making it a popular choice among discerning drivers.
