It started with a four-cylinder, graduated to six and then eight cylinders, and now might be settling back down to six. The next-generation F80 BMW M3, caught testing around the homeland, has let its voice be heard, and the suspicions are that a V6, not a BMW-traditional inline six, rumbles through those pipes.
Bimmerfile posits that a V6 could be "loosely based on the M5′s S63 twin-turbo V8, but with even greater high-end power and efficiency." Whatever is under that hood – and whatever is handling that lightning-quick gear change, don't quite sound like anything that's come straight from the factory before, at least to our ears. Follow the jump to watch and listen for yourself and make a guess in Comments.