2020 BMW X3 M and X4 M first drive: Velvet hammer

The X3 and X4 M share much of their mechanical musculature with the regular X3. But creating an authentic M experience requires engineers to go deep. And at the heart is a 3.0-liter twin-turbo straight six called the S58 that BMW says is 90 percent new and about 25 pounds lighter than the older high performance six-cylinder in the M3 and M4. The new forged crank alone weighs 6.6-pounds less. And speaking of forged internals, the stresses of turbocharging mean this motor uses those parts throughout and features a closed deck engine block design for added strength.
The cylinder head’s core was manufactured using a new 3D printing process that allowed engineers to create more intricate cooling passages than could be accomplished with the traditional process. To allow the S58 to spin past 7,000 rpm, it has a shorter stroke. The new engine’s 473 hp (503 hp in the Competition model) is achieved with 32 peak psi of boost (33.4 psi in Competition models) delivered from two mono-scroll turbos that serve three cylinders each and use an electronic wastegate to maximize the response. And helping to keep it all cool is a new water-to-air intercooler system.
BMW says it uses higher fuel pressures here, for more efficient mixing of air and fuel. And like other BMWs, these performance models use the company’s Valvetronic variable valve timing and Vanos variable cam timing. To keep the temperatures down on track, this BMW has a total of 6 (!) coolers including an additional engine oil cooler as well as a transmission cooler. A new dual chamber oil pan keeps oil circulating during aggressive moves on the track nearly as effectively as a dry sump system, according to BMW.