The new Porsche 911 Turbo Cabriolet models have been revealed, ahead of their official debut at the LA motor show in November.

The Cabriolet models are powered by the same 3.8-litre turbocharged flat-six engine as their 911 Turbo Coupe brothers.

In the standard model, this engine develops 520 bhp, and can accelerate from rest to 62mph in 3.5 seconds – 0.3 seconds down on the hard-top.

The S model, however, benefits from the full 560 bhp, and can complete the same sprint in 3.2 seconds, making it just 0.1 second behind the tin-top model.

Both can reach a top speed of around 197 mph, but also return 28.5 mpg on the combined cycle, with CO2 emissions of 231 g/km.

Power is sent to all four wheels through Porsche’s excellent dual-clutch PDK transmission.

The fabric roof has been revised, and now incorporates a lightweight magnesium frame that creates a more aerodynamic shape when closed.  The roof opens and closes in 13 seconds, and can be operated at speeds of up to 31mph.

The new 911 Turbo Cabriolet goes on sale in the UK in December 2013, priced from £126,766 for the Turbo Cabriolet, and £149,511 for the Turbo S Cabriolet.