The Porsche 911 will be completely overhauled this September. Out goes the classic 911 shape, and the growling, musical flat-six, air- cooled engine that has powered it for the past 34 years. The new 911 is longer, roomier and faster, and is both quieter and less polluting. The old air-cooled motor is replaced by a new water-cooled 3.4-litre flat- six, good for 300bhp. Turbo and cabriolet versions will follow in 1998. The car will be unveiled at the Frankfurt Motor Show in September. UK sales begin in November, with prices likely to start at about pounds 65,000.