The BMW 4 Series Cabrio was spied again during development testing on the Nordschleife racetrack in Germany. Unfortunately, the prototype continues to wear the same amount of camouflage as the last time we saw it. This new clip offers a chance to better hear its engine and exhaust. BMW is expected to sell the 4 Series cabriolet with a range of four- and six-cylinder engines, with power outputs ranging from 250 hp to 300 hp. We'll have more details regarding the BMW 4 Series cabrio as soon as they're available.