Porsche wheeled out a new Carrera, a convertible version of its newest update of the venerable 911 that adds both length and subtle trim changes to the line. Porsche president and chief executive Mattias Mueller rolled out the new drop-top at the annual Detroit auto fest, beaming as he declared the German maker\'s 2011 \"extremely successful.\" \"The new 911 cabrio is improved from the last model in every aspect,\" he said. The car has a 0-60 miles per hour (100 kph) acceleration in four seconds, but only has to slow down to 31 mph for the roof to be raised or lowered, he said. It also sports 15 percent better fuel consumption than its predecessors -- though fuel costs might be less important to the person who can spend $98,000 for the base model. \"We have built the best 911 in 49 years,\" he said. The new car is the convertible version of the 911 coupe introduced first in Germany in September, the seventh redesign of the half-century-old 911 line. Porsche\'s target is to sell about 25,000 of both the coupe and cabriolet this year. Mueller meanwhile cheered 2011 as \"one of the most successful years in our company\'s history,\" with a record 118,000 cars sold, up 22 percent over 2010. In North America sales jumped 15 percent to 29,000 units. China is the company\'s second biggest market, with 24,000 in sales last year, and the biggest market for its top-of-the-line Panamera, according to Porsche marketing chief Berhard Maier.