2012 BMW M6 Convertible first drive review: Agreeable anomaly

2012 BMW M6 Convertible

2012 BMW M6 Convertible

The 2012 BMW M6 Convertible is something of an anomaly. We doubt we’ll see many at track days, but there is no doubt that the M6 would excel on a road course. We know it more than shines on the open road, enough so that at a recent press introduction, five auto writers were unable to resist temptation and as a result had discussions with the California Highway Patrol. Five-hundred and sixty horsepower can do that to you, although not to this particular scribe.

But therein lies frustration. Repeat, it’s 560 horsepower. True, there are cars with more ponies under the hood, but not many. And fewer still, of course, with the top-down luxury of a BMW 6-Series two-plus-two. But what exactly does one do with it?

Well, one shouldn’t complain. Rather, slather on the sunscreen, drop the top and head out of the highway. Quickly. Zero-to-60 takes only 4.2 seconds.

2012 BMW M6 Convertible engine

The twin-scroll twin-turbo 4.4-lite V-8 of the 2012 BMW M6 Convertible is rated at 560 horsepower.

The sinew of the 2012 BMW M6 Convertible—it’s arriving now with the M6 Coupe arriving in late summer—is the same twin-turbo V-8 used in the BMW M5 sedan. The engine uses the same reverse-flow technology with the two turbochargers nestled in the vee between the banks of the V-8 with the exhaust routed from “inside” valves. The intake on the other hand comes from the outside of the vee, where the exhaust usually exits.

BMW claims a quicker response from the turbo, thanks to the short path from the exhaust valve to turbocharger turbine: “This exhaust manifold is a special 8-into-4 setup that combines the exhaust from two cylinders (on opposite banks) that are 360 degrees of crankshaft rotation apart from each other. Each of the eight runners is of identical length to ensure perfectly regular timing of exhaust gas pulses.”

Each of the four exhaust outlets goes into one of the two inlets on the twin scroll turbochargers. Timing of the exhaust pulses is optimized by the configuration, and because of the smaller port size, charge velocity is increased, which also improves turbo response. Maximum boost pressure is 21.7 psi.

The direct injection system allows multiple injections per combustion cycle, which not only allows ideal timing for fuel delivery but also, with the cooling effect of the gasoline evaporation lowers combustion chamber temperature, allows a 10.0:1 compression ratio, high for a turbocharged engine. The engine also uses BMW’s Valvetronic system that eliminates the throttle plate, replacing it with variable valve lift, and torque spread is controlled in part via BMW’s Double VANOS  infinitely-variable valve timing system.

2012 BMW M6 Convertible fender decoration

Chrome flash on the fender of the 2012 BMW M6 Convertible identifies the car as an M6.

The result is an engine produces around 10 percent higher output than the V10 engine of its predecessor with a torque increase of more than 30 percent. Fuel consumption, however, by the M6 Convertible down by 23 percent, based on EPA mileage estimates.

The only transmission available in the 2012 BMW M6 Convertible (or the Coupe, when it arrives, for that matter), is a seven-speed double-clutch automatic transmission. The transmission has three modes whether in manual or automatic operation. In fully automatic mode, D1 through D3 gets progressively sportier, while manual mode has three settings a well, S1 through S3. A “launch mode” is also available and provides the BMW M6 the quickest acceleration off the line for the traction available.