AutoExpress UK compares the new 2013 BMW M6 Convertible against a similar offering from Mercedes-Benz, the SL63 AMG. The M6 is powered by the S53Tu 4.4 liter V8 TwinPower turbocharged engine employing the M division’s patented manifold that evenly spaces out exhaust pulses. With a peak turbo boost of 21.7 psi, the M-built engine produces 560 hp and 500 lb-ft of torque that now is delivered in a flat band between 1500 and 5750 rpm.

The performance is also possible thanks to twice as large intercoolers compared to the ones found in the X5M/X6M models and of course, the unique Valvetronic. Compared to the highly-acclaimed, now retired, 5.0 liter V10, the new unit found in the M5 and M6 not only has 10 percent more ponies, but it also improves its efficiency by nearly 30 percent, in part thanks to the engine stop-start feature.

See our test drive of the 2012 BMW M6 Convertible

Based on the SL-Class that debuted at the 2012 Detroit Auto Show, the SL63 AMG packs a twin-turbo 5.5 liter V8 producing 529 horsepower (557 with AMG Performance Package) and 664 lb-ft of torque. The new SL63 AMG can rocket from 0-62 mph in 4.3 seconds (4.2 with the optional AMG Performance Package) while returning 30 percent better fuel economy. Top speed rises to 186 mph.

The SL63 AMG is being picked by AutoExpress as the winner of this comparison, but there are a few things worth pointing. The M6 is a Gran Turismo car with space for four, therefore weighing more, while the SL63 is a high-end roadster seating two people. One other important factor is the lack of ceramic brakes on the M6, an important detail that on track has the highest impact on the performance of a car.

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