Porsche's sleekly styled flagship 911 recently added new Carrera 4 and Carrera 4S all-wheel-drive coupes. The AWD system has a multi-disk viscous coupling and transfers between five and 40 percent of the engine's power permanently to the front wheels, affording both cornering abilities that just about violate the laws of physics, and improved traction on slippery roads. Read full story here.