Porsche is stuffing a built twin-turbocharged 4.0-liter into the Cayenne Coupe, and it's the most powerful V-8 the German automaker has ever produced. It makes 631 horsepower in this new Turbo GT model, and Porsche says its factory driver Lars Kern set a new SUV lap record at the Nürburgring Nordschleife in it lapping the 12.9-mile course in 7:38.9. The new Cayenne will arrive in the U.S, only in Coupe form, next year starting at $182,150.