It's twins! The new BMW M6 Coupe and BMW M6 Convertible have both emerged simultaneously from their creator, the German car maker's go-fast division M GmbH.
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And fast they are. The BMW M6 Coupe takes the company's quickest cars closer than ever to 4.0 seconds for the 0-100km/h sprint, with a time of 4.2 seconds.

The BMW M6 Convertible, despite the weight baggage of a retractable roof system, is a smidge behind at 4.3 seconds but half a second quicker than before and matched to the BMW M5 with which they much in common.

Like the M5, which launched locally last week (click to read our BMW M5 Review), the M6 Coupe and Convertible - which a local ETA of October - switch from their predecessor's high-revving naturally aspirated V10 to a more powerful twin-turbocharged 4.4-litre V8.

Hit 6000-7000 revs and the bi-turbo V8 sends its maximum 412kW to the rear wheels via a seven-speed dual-clutch auto and (again from the M5) and Active M differential that shuffles power between the left and right rear wheels for optimum traction.

The engine's broader strength compared to the old V10 is epitomised by 680Nm of torque delivered from as low as 1500rpm, though while outputs and performance are up, fuel efficiency and emissions are also improved by about 30 per cent.

The M6 Coupe officially slurps 9.9 litres of fuel per 100km and emits 232 grams of CO2 per kilometre, with the M6 Convertible offering figures of 10.3L/100km and 239g/km.

Increased performance and efficiency comes despite both the Coupe and Convertible piling on the kilos for their latest-generation form, with the fixed-roof M6 adding 140kg to the scales and the folding-roof M6 gaining 50kg.

Both M6 models, of course, were extensively tested at Germany's Nurburgring circuit, with both chassis honed for a greater level of agility than the regular 6-Series models.

Tracks are widened by 30mm compared to the 6-Series Coupe and Convertible and both cars sit on 19-inch alloy 'M' wheels as standard, with 20-inch wheels optional.

The M6 Coupe again comes with a carbonfibre-reinforced plastic (CRFP) roof that lowers the car's centre of gravity.

The M6 Convertible also copies its predecessor, offering a soft-top hood that opens electrically in 19 seconds and closes via the same single button in 24 seconds. The operation can be performed both at standstill or up to a speed of 40km/h.

The M6 Coupe reaches 200km/h from standstill half a second quicker than the Converitible (12.6 v 13.1sec), though both M6 models will hit a 250km/h maximum speed unless owners pay extra for the M Driver's package that overides the electronic governor to hit 305km/h.

BMW M cars are renowned for having excellent brakes, though if the standard stoppers on the M6 Coupe or Convertible aren't sufficiently big or strong enough then carbon-ceramic brakes are optional.

The M6 interior is a two-tone affair, at least for the M6 Convertible pictured above. Sportier touches over the 6-Series include carbonfibre trim for the centre console, dash strip and part of the door trim, a thick-rimmed M steering wheel and perforated 'M' driver's footrest.

The previous M6 Coupe and Convertible, launched in 2005 and 2006 respectively and discontinued in 2010, cost $292,555 and $313,316. If the pricing for the new BMW M5 is any guide, expect those prices to drop by up to five figures.

If you want to see the new BMW M6 models in the flesh before they reach Australia in October, you'll need to head to the 2012 Geneva motor show in March for the Coupe and the 2012 New York motor show in April for the Convertible.

A third M6 model - not yet officially confirmed - is expected to appear at the 2012 Paris motor in September in the form of the BMW M6 Gran Coupe - the company's four-door version of the 6-Series Coupe that is a rival for the Mercedes-Benz CLS.