The M-ified version of the BMW 4-Series, appropriately called the BMW M4, is headed our way soon. We know it will have turbo power, but we don't know how much yet. Today, we know what it might sound like.

BMW just released this teaser on YouTube of some mysterious, unseen yellow M car as it revs its engine in a lab setting. Could it be the M4, or possibly the M3 sedan? More than likely, yes, unless BMW has some insane other M-surprise up their sleeves we don't know about.

Odds are, this engine will be a turbocharged inline-six, which will be a nice return to form for the M3 and now M4. It sounds pretty rowdy here. Let's hope they don't have to pipe it in through the speakers.