The muscle car is a simple recipe written by Detroit in the 1960s. Start with one heaping cup of fire-breathing power plant. Add two rear wheels slinging the power to the road and a manual transmission to taste, then garnish with a sleek, sexy shell. Simple, yet effective. Like any simple recipe, though, someone always comes along with the artisan take. The result is essentially the same, but with a waft of complexity and pretension, much like the E6X M5 and M6.

BMW isn't the first thing that comes to mind when discussing muscle cars, but the formula fits. One screaming 5.0L V10 at the front, power sent to the rear wheels, and one big grin gleaming through the tire smoke. Like their American cousins, the Deutsche Braun Bimmers need adequate cooling to perform their best. Specifically, they