BMW’s 3 Series gets more powerful engines, enhanced interior accoutrements, new exterior colors, and a new, 2-door coupe version for the 2007 model year. But the coupe isn’t the only new version that expands the 3 Series lineup, which in 2006 included only a sedan and sport wagon. A new 3 Series convertible with a retracting hard top will be added as a 2008 model.