The new Porsche 911 Cabriolet, announced in November 2011, will make its world debut at the upcoming NAIAS in Detroit. The first motor show of the year was chosen because America is the biggest market for the drop top, by far. In fact, Porsche is thriving in the US despite the less than rosy economy – in 2011, Porsche sold 29,023 cars, 15% up from 2010. They plan to shift over 30k units this year.

Back to the 911 Cab. The big news here is the all new roof design. Throwing out the multi-layered fabric item from the 997, this lid uses a fabric skinned composite panel, which provides a nicer shape and a better fit. Porsche also says that this new roof, which takes just 11 seconds to raise or stow, is more resistant to high speed buffeting. There’s also an automatic wind deflector.

The roof is laid on a magnesium frame, and the glass rear window is glued directly to the outer fabric skin. The lowering and closing process can be done at speeds of up to 60 km/h. You can see this being done in the videos.

Powertrains are identical to the 991 Coupe. The Cabrio’s backside houses a 3.4-litre flat six with 350 hp/380 Nm driving the rear wheels via the world’s first seven-speed manual gearbox. The Carrera S Cabriolet comes with a 3.8-litre flat six with 400 hp and 440 Nm. Porsche’s twin-clutch PDK will be a popular option, delivering better fuel consumption and acceleration than the stick shift.

Click here for full details and a gallery of the 911 Cabrio.