Porsche Recalling 911 Models for Exhaust System Problem Porsche is recalling about 2,263 of its 2012-13 911 models because part of the exhaust system can fall off. In a report posted on Friday on the Web site of the National Highway National Highway Traffic Safety Administration, Porsche said the models were the 911 Carrera, 911 Carrera Cabriolet, 911 Carrera 4 and the 911 Carrera 4 Cabriolet equipped with the 3.4 liter, 6-cylinder engine and the standard rear muffler exhaust system. Models with the optional sport exhaust are not affected. The automaker said its internal testing showed the exhaust systems "do not achieve the required service life" and might fracture, allowing the end to fall off. Porsche said it first noticed the problem on a high-mileage test vehicle last May and began an investigation. It recently concluded a recall was needed, although company officials told the safety agency they were not aware of any failures on vehicles owned by consumers. Porsche described the recall as voluntary, but under federal regulations once a manufacturer learns of a safety problem it has five working days to inform the agency of a recall or face a civil fine. In December, Porsche had recalled 455 of its 911 GT3s from the 2010 model year saying the rear wheel hub might come off.