BMW has confirmed that its upcoming M350 M Performance 3 Series will rely on a familiar powertrain formula rather than a fundamentally new engine. The sedan uses the company's turbocharged B58 inline-six, now paired with 48-volt mild-hybrid assistance, an eight-speed ZF-sourced automatic transmission and xDrive all-wheel drive. When asked whether the M350 employs the same updated B58 already found in the X3 M50, BMW confirmed that it does, with differences limited to application-specific tuning and a revised cooling setup.
The result is a notable step up from the outgoing M340i. In the United States, the M350 is rated at 437 horsepower, while German-market specifications quote 443 PS. Torque stands at 580 Nm (428 lb-ft), placing the new sedan well above its predecessor in both power and pulling force. The output also settles a lingering question for enthusiasts: BMW will not detune the M Performance 3 Series for the European market as it did with the M340i.
The most significant engineering detail concerns where the extra performance comes from. An engineer involved with the project revealed that the additional torque is largely a product of the hybrid system rather than the combustion engine itself. BMW retuned the turbocharger to extract the extra horsepower, but the mild-hybrid setup is responsible for almost all of the torque increase. The 48-volt system can contribute around 40 Nm (nearly 30 lb-ft) directly to the transmission, filling the gap before the turbocharger has fully spooled up.
This approach gives the powertrain a stronger initial shove while the B58 builds boost, a more sophisticated solution than simply fitting a larger turbocharger. The electric motor effectively smooths the transition between low-rev response and full forced-induction thrust, making the car feel more immediate from a standstill and during mid-range acceleration.
Despite the gains, BMW suggests the difference will not be night and day from behind the wheel. Drivers comparing the M350 with an M340i would probably struggle to notice the extra assistance unless they drove the two cars back-to-back. Nevertheless, the development marks another example of BMW using mild-hybrid technology for more than just improving fuel economy and emissions as regulations tighten across global markets.
The M350's output also resets the pecking order among inline-six models. The Toyota Supra Final Edition had briefly held the title of most powerful version of the B58, though that comparison was complicated by the fact that the M350's figure factors in hybrid assistance. Even so, the new sedan's numbers are significant for what they imply about the wider range. With the M Performance model producing this much power, expectations are rising for the next-generation M3, codenamed G84, which is widely expected to deliver more than 500 hp even in its most basic form.
BMW will want to maintain a clear distance between its two M flavours, and an M3 starting with a four would not feel right to the brand's engineers or its customers. The M350 breaks cover at the end of this month, while the petrol-powered M3 is not expected to arrive until 2028 at the earliest, leaving a long wait to discover exactly how many horses will separate the two models.