PHOENIX — RDX is Acura’s premium compact to mid-sized crossover utility vehicle that first arrived for 2007. With its turbo-powered engine and upscale appointments, it was an enjoyable vehicle to drive but, unfortunately, didn’t catch on with the car-buying public. Later, the second-generation RDX added more luxury and a standard 279-horsepower 3.5-liter V-6 engine. But it was predominantly a gussied up Honda CR-V, sharing the same basic chassis architecture.