Sunday, April 19, 2009

The first modern turbocharged M engine:

Using BMW’s innovative, 4.4L reverse-flow V8 engine with High Precision Direct Injection and twin turbochargers as a basis, the new M engine introduces twin-scroll twin turbochargers and patented exhaust manifold technologies to achieve outstanding thrust and pulling force, while preserving the most compact dimensions possible. Two low-mass twin-scroll turbochargers are positioned together with the catalytic converters in the “V” section between the two banks of cylinders. By reversing the flow of gases through the engine from traditional arrangements, the intake and exhaust ducts are shortened and widened. The result is that pressure losses on the exhaust side are minimized.
The goals: virtually eliminate turbocharger lag while maximizing combustion efficiency and power output. Tremendous power and performance are delivered by the engine in the BMW X5 M and BMW X6 M through a new design and construction principle. The new M V8 engine with twin-scroll twin turbo technology uses a single exhaust manifold with tuned-length runners, incorporating both cylinder banks and connecting cylinders in carefully-selected pairs.
This configuration, patented by BMW M and known as Cylinder-bank Comprehensive Manifold (CCM), offers lightning-quick response, a linear build-up of engine power, and a broad, consistent torque curve by feeding each of the twin turbochargers with a “charge pulse” at approximately every 90 degrees of crankshaft rotation, rather than the more traditional “irregular schedule” of charging.
The managed flow of exhaust gas provided by the CCM ensures high-velocity flow of combustion gases. The appropriate separation of exhaust gas flow from different cylinders is maintained until the gas reaches the turbine wheel, spooling the two twin-scroll turbochargers without back-pressure.
With maximum boost pressure of 1.5 bar (21 psi), the use of twin-scroll twin turbo technology and the CCM exhaust manifold allows complete exploitation of the benefits of turbocharging.

No comments:

Post a Comment