The BMW M5 is back!

BMW's M division has gone back to the drawing board with the M5, giving the fifth generation of the iconic four-door a twin-turbocharged 4.4-liter V8 engine—the first time Munich's class-defining performance sedan has gone without a naturally aspirated powerplant since its introduction in 1984.

Further changes see it adopt a dual-clutch gearbox as part of a complete driveline rethink that resigns the old model's sequential manual transmission to the history books.

Revealed here officially for the first time, the new M5 is planned to make its world debut in concept-car guise at the Shanghai motor show later this month.

A virtually unchanged production version, undergoing the final phase of a 24-month test and development program in the hands of BMW M division engineers, is planned for the Frankfurt motor show in September prior to the start of North American sales in 2012.

With 560 hp and a thumping 510 lb-ft of torque, the engine serves up a noticeable 60 hp and 127 lb-ft more than the outgoing model's more high-strung 5.0-liter V10. It's also up by 160 hp and 60 lb-ft on the 550i, which uses BMW's standard turbocharged 4.4-liter V8.

No official performance claims have been made yet, but M division engineers involved in the new car's development have revealed to AutoWeek that acceleration has been improved by up to two-tenths of a second. This points to a 0-to-62-mph time of about 4.5 seconds--equaling the straight-line performance of its main sedan rival, the Mercedes-Benz E63 AMG.

Top speed, like all M cars, will be limited to 155 mph, although the taller individual gearing and longer final drive ratio made possible by the significant increase in torque should see the new car's theoretical top speed rise to more than 180 mph.

BMW also claims the mill provides a 25 percent improvement in fuel economy over the outgoing V10 thanks to the inclusion of features such as brake-energy recuperation, an alternator that disengages under acceleration and an automatic stop/start function--all part of the German car maker's EfficientDynamics initiative.

As well as seeing service in the M5, the new engine is also set to appear in the second-generation M6 coupe and convertible, both set to reach the U.S. market by the end of 2012. BMW officials also hint that the potent V8 is earmarked for a range-topping version of the four-door GranCoupe, which is being groomed as Munich's answer to the recently introduced Mercedes CLS63 AMG.

The engine channels drive to the rear wheels through a Getrag-engineered seven-speed dual-clutch gearbox with steering-wheel-mounted shift paddles, offered as an option on the M3. Supporting both full manual and automatic modes, it promises to provide much smoother operation and improved usability over the rapid but sometimes clunky sequential seven-speed gearbox it replaces.

The fresh M5's underpinnings are loosely based on those of the latest 5-series, but as with all of its predecessors through the years, the individual components are mostly unique. The model adopts a double-wishbone suspension at the front in place of the MacPherson-strut setup that has been a mainstay of the M5 for the past 25 years. The rear retains an independent multilink arrangement but now carries a greater number of aluminum parts. Variable damping control provides the choice of three different levels of suspension stiffness. Yet to be confirmed is a switch to an electronic steering system--another first for the BMW's performance sedan.

The styling changes are relatively slight. But the discreet visual modifications, developed in the German carmaker's new state-of-the-art wind tunnel in the heart of Munich, help give the M5 a traditionally more purposeful appearance than its standard sibling. Included on the concept bound for Shanghai is a deeper front bumper housing a trio of air ducts and modified front fender panels.

At the rear, there is a subtle lip spoiler attached to the trailing edge of the trunk to provide increased levels of high-speed downforce and a reprofiled bumper with a fully functioning central-diffuser element and fluted sections to the sides, each housing a pair of round chromed tailpipes. It's all rounded off with a set of 20-inch alloy wheels.

By Greg Kable