BMW X6 M

The BMW X6 is a mid-size luxury crossover released for sale in the second quarter of 2008 by German automaker BMW. The X6 was marketed as a Sports Activity Coupé (SAC) by BMW. It combines the attributes of an SUV (high ground clearance, all wheel drive and all-weather ability, large wheels and tires) with the stance of a coupé (bold styling, dramatic sloping roof).

BMW X6 M (2009-)

The BMW X6 M and BMW X5 M are the first xDrive all-wheel-drive vehicles from the M GmbH. The vehicle was unveiled in 2009 New York Auto Show.^[10]
The high-performance M derivative features a twin scroll twin turbo version of the 4.4-liter V8 BMW N63 engine with Cylinder-bank Comprehensive Manifold (CCM). Engine is rated 555 PS (408 kW; 547 hp) at 6000 rpm and 680 N·m (500 lb·ft) at 1500-5650 rpm.

Other features include 6-speed M Sports Automatic transmission with aluminum pull-style paddles on steering wheel, M Dynamic Mode feature, 10 mm (0.4 in) lower Adaptive Drive suspension, 4-piston fixed calipers with 15.6" rotor at front and single piston floating calipers with 15.2" rotor at rear, 20-inch alloy wheels with 275/40R20 front and 315/35R20 run flat tires, special gills in the front fenders, 20-inch light-alloy wheels.^[11]
The car can accelerate from zero to 60 mph (0–97 km/h) in 4.5 seconds and 0-62 mph (0-100 km/h) in 5 seconds.^[12]

Dynamic Performance Control

Engine

Using BMW’s “M TwinPower Turbo” unit 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 increase 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 were to virtually eliminate turbocharger lag while maximizing combustion efficiency and power output. 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 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.

Coupled with special suspension specifically optimized for M that features Adaptive Drive and the newly developed M Servotronic power steering, the performance Sport Activity Vehicle promises very competent handling. Other high-tech features include launch control for maximum acceleration and a six speed M Sport automatic transmission optimized for performance. Drivers can manually select gears using either paddles or an electronic gear selector lever. Electronically controlled, variable power distribution to the front and rear axle prevents even the slightest tendency to over- or understeer right from the start, before DSC Dynamic Stability Control is even required to cut in. BMW is referring to the new 4.4-liter motor as its “M TwinPower Turbo” unit. The name reflects the fact that the motor features Twin Scroll Twin Turbo Technology and a common exhaust manifold encompassing both rows of cylinders. Although traction control is standard, the M Dynamic Mode (MDM) greatly optimises the aggressiveness of the system. The MDM setting allows the driver to enter a controlled drift and push the vehicle’s handling to the limit. There is also a DSC-Off Mode.

Dynamic Performance Control

The X6 marks BMW's first use of its new Dynamic Performance Control system, which works in unison with xDrive all-wheel drive (both are standard on the X6). DPC is a drivetrain and chassis control system that works to regulate traction and especially correct over- and understeer by actively spreading out drive forces across the rear axle. Torque is split not only between the front and rear wheels (xDrive) but also from side to side at the rear for improved agility and added stability (through the DPC rear axle). ^[16]



The DPC differential features clutch packs on both output sides that are actuated by an electric motor. The clutch pack activates a planetary gearset which causes one wheel to be overdriven. A conventional control system will use the brakes to reduce the speed of the faster moving wheel (which is the one with less traction)and reduce engine power. This leads to increased brake wear and slower than optimal progress. The DPC system speeds up the slower moving wheel (the one with the most traction) in order to maintain stability when needed. For example; while turning, the outer wheel is overdriven to provide greater acceleration using the traction advantage through the dynamic loading of the outboard wheel in cornering. In an oversteer situation, the inner wheel is overdriven to regain traction balance.