German OEM BMW has detailed the six-cylinder in-line engine developed exclusively for its new M340i. Developed to produce instant power, the 3-liter power unit features an aluminum crankcase with a closed-deck construction and an alloy cylinder head.
Weight-minimized pistons and con rods and a crankshaft made from forged steel increase internal engine efficiency. Frictional losses are reduced through ‘form honing’ of the cylinder bores in the crankcase.
The new straight-six generates 379ps, and peak torque levels of 500Nm. The unit’s M TwinPower Turbo technology includes a twin-scroll turbocharger with indirect charge air cooling integrated into the intake system, latest-generation direct gasoline injection, Valvetronic fully variable valve timing and Double-VANOS variable camshaft timing for the intake and exhaust sides.
Integrating the turbocharging system into the cast-steel manifold results in a compact engine design and ensures that the exhaust flow only has short distance to travel, allowing charge pressure to develop rapidly from low revs.
The turbine’s responsiveness is further enhanced by a 25% reduction in the mass moment of inertia. A wide-opening, electrically controlled wastegate helps to keep emissions down. The maximum operating pressure of the direct injection system, with its cantilevered injectors, is 350 bar. This optimizes fuel metering and also minimizes the engine’s emissions.
BMW’s efficient cooling system ensures the engine, transmission and brakes are kept at an ideal operating temperature. The cooling solution comprises a high-temperature and a low-temperature circuit, plus indirect charge air cooling. A split-cooling valve makes it possible to temporarily shut off crankcase cooling, thereby optimizing warm-up behavior.
The new straight-six power unit is paired with BMWs latest-generation 8-speed Steptronic Sport transmission. This system is equipped an optimized hydraulic control system, low converter slip, and effective damping of rotational irregularities.