By John Teresko Rotary-engine car buffs braving Detroit's North American International Auto Show last week got a treat in the Mazda Motor Corp. booth. On display was the RX-8 concept vehicle -- which is likely to succeed the company's legendary RX-7, a two-door sports car first offered in 1978. The updated version, a sports sedan, is powered by a naturally aspirated two-rotor engine that is 30% lighter than its predecessor, says Phil Martens, managing director, product strategy, design, and product and powertrain development. He says the RX-8's engine will have up to 280 hp at 9,000 rpm and is expected to meet stringent global emission standards at launch. Specifications for the four-door prototype list seating for four full-sized adults, a 106.3-in. wheelbase, rear wheel drive, and a six-speed transmission with auto/manual shift. Mazda says the RX-8 is much closer to an actual production sports car than the RX-EVOLV, the prototype it displayed at last year's show.