SPY SHOTS: 2011 BMW M5 with Twin-Turbocharged V8

Having already introduced the next generation 5-Series sedan, BMW and in particular, its M division, is now concentrating on the development of the flagship version of the series, the M5 that was caught here testing at the Nordschleife. The hotly anticipated M5 will debut about a year after the standard 5-Series that is due to make its first public appearance at the 2010 Geneva Show next March.

Until recently, it wasn't clear if the new M5 would continue to use the current model's exotic V10 powerplant or if the Bavarian's would go for the new 4.4-liter bi-turbo V8 that debuted in the X5M and X6M. However, BMW officials have now confirmed that the new M5 will indeed be equipped with the turbocharged V8.

In the X5M and X6M, the bi-turbocharged unit produces an output of 555 horsepower at 6,000 rpm and 680Nm or 501-lbs/ft of peak torque, available between 1,500 and 5,650 rpm. In comparison, the current M5's naturally aspirated V10 makes 507HP and 520Nm or 383-lbs/ft of peak torque.

Details on the new M5's engine specs remain scarce, though it has been suggested that the direct-injection V8 may be further honed, boosting output closer to the 600HP mark.

The new V8 will not only be more powerful than the V10, but also more compact in size, lighter in weight and more fuel efficient with lower CO2 emissions.

Along with the new powerplant, the 2011 M5 will get a re-engineered version of the BWM M3's seven-speed twin-clutch transmission (DCT), and hopefully for purists, a classic manual gearbox.

As with every other product bearing the M badge, the 5-Series-based model will benefit from suspension, brake and steering system upgrades to further improve handling and driver's feedback.

Even though the prototype model seen in these spy pictures features the standard roof, it is rumored that BMW is working on a carbon fiber top similar to that of the current M3 and M6. Other cosmetic differences will include engorged wheel arches housing larger rims and of course, a full body kit.

If BMW keeps its usual time schedule, we should see the new M5 breaking cover at a major auto show in 2011, with sales starting in Europe towards the end of the same year, and the rest of the world including the U.S., in 2012.