BMW X6 and X5 get the M treatment
BMW has done the inexplicable inevitable, expanding its M treatment from cars to SUVs (or Sports Activity Vehicles in BMW parlance). The New York Auto Show marks the world debut of the X5 M and X6 M, and in typical M fashion, the high riders get substantially more power than their more pedestrian variants. Both vehicles get uprated versions of the 4.4-liter twin-turbocharged V8 that debuted in the X6 last year. Power goes from a mere 400 hp up to 555 hp in M form with torque swelling from 450 to 500 lb-ft. While the increase in twist doesn't seem like all that much, BMW is claiming it's produced from 1,500 all the way to 5,650 rpm.
The 4.4-liter V8 is direct injected and like other such engines with turbos, torque aplenty is the result. Like the standard version of the V8, the M variant has the intakes on the outside of the cylinder heads with the exhaust and twin turbos planted in the valley between the banks. This new version sports a revised exhaust manifold that combines the flow from both banks into the duo of twin scroll turbochargers.
The exhaust runner lengths have been tuned to ensure each turbo gets a pulse of exhaust pressure for every 90 degrees of crank rotation, allowing a steady flow to keep them spinning. The charge cooling effect of direct injection along with a pair of water-to-air intercoolers allowed the M engineers to crank maximum boost to 21 psi. We can't wait to see this engine in the next generation M5 in a year or two, providing a real challenge to the new CTS-V.
An important element of all new BMWs is Efficient Dynamics. While these two vehicles aren't particularly "efficient" in the grand scheme of things, BMW has tried to make the most of what's available. Parasitic losses are kept to a minimum through features like an electric fuel pump with on-demand control, as well as similar control for the air conditioning compressor and a flow control system to drive hydraulic fluid to the active roll control system.
BMW's M models aren't just about engines -- they're about providing a well-rounded package that begins and ends with handling. To that end, the active roll stabilization and adaptive drive systems get the most out of the fairly heavy X6. The torque vectoring all-wheel drive system has been enhanced and a new driver activated M button triggers higher activation thresholds for the stability control and optimizing for other settings. The brakes definitely appear to be up to the task of hauling down 5,000+ pounds of X6 M with 15.6-inch rotors in front and 15.2-inch discs in the back.
The Ms also get the prerequisite visual modifications, including a gaping front fascia that openings to accommodate the air flow required to feed and cool the powerplant. At the back, a revised rear fascia features the BMW's trademark four outlet exhaust, while each corner is fitted with new 20-inch alloys wrapped in 275/40 tires at the front and 315/35 rubber in the rear.
