The BMW 3 Series M340i, specifically the G20 LCI (Life Cycle Impulse – facelift) model introduced in 2022, represents a high-performance variant within the iconic 3 Series lineup. Production of this iteration began in July 2024. Positioned as a near-flagship sedan, it bridges the gap between the more mainstream 3 Series trims and the fully-fledged M3. The M340i distinguishes itself through a potent turbocharged inline-six engine, a mild-hybrid system, and a focus on delivering a dynamic driving experience. It’s a four-door sedan designed to appeal to enthusiasts seeking both luxury and performance in a practical package, primarily targeting the North American and European markets.
Technical Specifications
| Brand | BMW |
| Model | 3 Series |
| Generation | 3 Series Sedan (G20 LCI, facelift 2022) |
| Type (Engine) | M340i (386 Hp) Mild Hybrid Steptronic |
| Start of production | July, 2024 |
| Powertrain Architecture | MHEV (Mild Hybrid Electric Vehicle) |
| Body type | Sedan |
| Seats | 5 |
| Doors | 4 |
| Fuel consumption (urban) | 8.7 l/100 km (27 US mpg) |
| Fuel consumption (extra urban) | 7.1 l/100 km (33.1 US mpg) |
| Fuel consumption (combined) | 8.1 l/100 km (29 US mpg) |
| Fuel Type | Petrol (Gasoline) |
| Acceleration 0 – 60 mph | 4.4 sec |
| Maximum speed | 210 km/h (130.49 mph) |
| Weight-to-power ratio | 4.5 kg/Hp |
| Weight-to-torque ratio | 3.2 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.) |
| System power | 386 Hp @ 5200-6250 rpm |
| System torque | 540 Nm @ 1900-4800 rpm (398.28 lb.-ft.) |
| Engine layout | Front, Longitudinal |
| Engine Model/Code | B58B30M2 |
| 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 | 11:1 |
| Number of valves per cylinder | 4 |
| Fuel injection system | Direct injection |
| Engine aspiration | Twin-power turbo, Intercooler |
| Valvetrain | VALVETRONIC, Double-VANOS |
| Kerb Weight | 1739-1767 kg (3833.84 – 3895.57 lbs.) |
| Max. weight | 2260 kg (4982.45 lbs.) |
| Trunk (boot) space | 480 l (16.95 cu. ft.) |
| Fuel tank capacity | 59 l (15.59 US gal) |
| Length | 4723 mm (185.94 in.) |
| Width | 1827 mm (71.93 in.) |
| Height | 1433 mm (56.42 in.) |
| Wheelbase | 2851 mm (112.24 in.) |
| Number of gears | 8 |
| Gearbox type | Automatic transmission Steptronic |
Powertrain & Engine Architecture
At the heart of the M340i lies the B58B30M2 engine, a 3.0-liter turbocharged inline-six cylinder powerplant. This engine is a descendant of BMW’s long-standing tradition of smooth and powerful six-cylinder engines. The B58 features 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 deliver a broad torque curve and responsive performance. The addition of a 48V mild-hybrid system provides a small power boost (11 hp) and enables features like smoother auto start-stop operation and some coasting functionality. The engine is paired with an 8-speed Steptronic automatic transmission, known for its quick and precise shifts. This transmission is designed to handle the engine’s substantial torque output and offers both automatic and manual shift modes.
Driving Characteristics
The M340i delivers a noticeably more engaging driving experience than the standard 3 Series models. The 386 hp and 398 lb-ft of torque provide brisk acceleration, with a 0-60 mph time of just 4.4 seconds. The 8-speed automatic transmission is well-tuned, offering smooth upshifts and downshifts, and responding quickly to driver inputs. The mild-hybrid system contributes to a seamless power delivery. Compared to the 330i, the M340i offers significantly more power and torque throughout the rev range. While the 330i prioritizes fuel efficiency, the M340i leans towards performance. The chassis is also tuned for a sportier feel, with stiffer springs and dampers, and more responsive steering.
Equipment & Trim Levels
The M340i typically comes well-equipped as standard. Common features include leather upholstery, a premium sound system, a large infotainment display with iDrive, and a suite of advanced driver-assistance systems. Optional extras often include a head-up display, adaptive cruise control, parking assist, and upgraded interior trim options. The M Sport package is a popular option, adding more aggressive styling cues, sport seats, and an M Sport suspension. Interior trim options range from aluminum to wood, allowing for a degree of personalization.
Chassis & Braking
The M340i features a robust chassis designed to handle the increased power. 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. This configuration provides a good balance of comfort and handling. Braking duties are handled by ventilated discs at all four corners, providing ample stopping power. The M Sport brakes, an optional upgrade, offer even greater stopping performance with larger rotors and calipers. The steering system is an electric power-assisted rack and pinion system, providing precise and responsive steering feel.
Market Reception & Comparison
The M340i has been widely praised by automotive critics for its blend of performance, luxury, and practicality. It’s often seen as a sweet spot in the 3 Series lineup, offering a significant performance upgrade over the base models without the higher price tag and more track-focused nature of the M3. Fuel economy is respectable for a performance sedan, with combined EPA ratings around 29 mpg. Reliability has generally been good, although some owners have reported minor issues with the infotainment system. Compared to rivals like the Audi S4 and Mercedes-AMG C43, the M340i is often favored for its engaging driving dynamics and refined engine.
Legacy
The G20 M340i represents a modern interpretation of the classic BMW sports sedan formula. The B58 engine has proven to be a durable and reliable powerplant, and the 8-speed Steptronic transmission is also known for its longevity. On the used car market, well-maintained M340i models hold their value relatively well, reflecting their desirability and performance credentials. The combination of a powerful engine, a comfortable interior, and a sporty driving experience ensures that the G20 M340i will likely remain a sought-after vehicle for years to come.
