World's Fastest Four-Door Sedans

Porsche is full of surprises. A few years back it introduced the Cayenne SUV. Much to the chagrin of the Porsche faithful, the SUV has proven such a sales hit that it encouraged the German sports car company to introduce its first four-door, the Panamera. With style influenced by the iconic 911, this practical four-seat supercar went on sale October 17. The 2010 Panamera Turbo, sporting a 500-horsepower twin-turbo 4.8-liter V-8 and seven-speed PDK gearbox, doesn’t stop charging until its top speed of 188-mph is reached. But this new Porsche is not quite the world's fastest sedan.

The Maserati Quattroporte Sport GT S wraps 440 horsepower in a stylish shape that could only be Italian. The evocative exterior comes from the design house of Pininfarina, and the powerful V-8 is sourced from Ferrari. Top speed exceeds 177 mph and 0-60 mph comes up in just five seconds. This svelte sports sedan will humble most sports cars despite its two extra doors.

Mercedes-Benz produces a handful of very powerful and sporting sedans. Some produce over 600 horsepower, but the swoopy CLS63 AMG does just fine with its hand-built 6.3-liter, naturally-aspirated, 507-horsepower V-8. The engine is a velvet-covered sledgehammer that launches the CLS like a rocket from zero to 60 mph in just 4.3 seconds. Its top speed of 155 mph is electronically limited, but left unfettered, it would easily top 180 mph.

The conservative and practical BMW 5-Series sedan provides useful transportation for thousands of drivers the world over. Equipped with frugal, clean-diesel engines, the sedan is a model environmental citizen ... a do-gooding Dr. Jekyll of sorts. But Mr. Hyde emerges from the 5-Series line when outfitted as the M5. This edition uses a Formula 1-derived, high-revving V-10 engine that produces 500 horsepower and delivers devilish performance with room for five. Sixty mph comes up in only 4.1 seconds according to some reviewers. Like the Mercedes-Benz, top speed is self-limited to 155 mph. Killjoy goodie-two-shoes…

The Cadillac CTS-V upstages German and Italian super sedans with (gasp, how crude) a push-rod, cam-in-block V-8 with an ancestry that dates back to the 1950s. As equipped, the Cadillac CTS-V's 6.2-liter V-8 is fortified with a supercharger to pump out a staggering 556 horsepower. Cadillac claims, and testers confirm, that the CTS-V can hit 60 mph in less than four seconds, and that versions with a six-speed manual gearbox will top out at 191 mph! Unlike American performance cars of yore, this Cadillac can turn and stop. Proof that this claim isn't marketing hype comes from the CTS-V currently holding the lap record at Germany's famed Nürburgring circuit for a production sedan running on stock tires. Adding insult to the injuries the CTS-V inflicts on its European competition, the Cadillac costs tens of thousands less than its slower rivals.

You're looking at the world's fastest four-door, with a top speed of an even 200 mph. The maker is neither Italian nor German, as one might expect. The Continental Flying Spur Speed is a Bentley, the stately British marque. Powered by a 6.0-liter twelve cylinder arranged in a double-V, or W configuration, the twin turbocharged engine produces an even 600 horsepower. The power runs through a sophisticated six-speed automatic and all-wheel drive system. While this exclusive and expensive Bentley offers much, fuel economy is not its forte. City mileage is only 10 mpg.

First shown over three years ago as a prototype, the production Aston Martin Rapide is almost ready to go on sale. The ultra-luxury sport sedan made its production debut recently at this Fall's Frankfurt Auto Show. With "only" 470 horsepower from its hand-built 6.0-liter V-12, it is unlikely that the Rapide will dethrone the Flying Spur in regards to top-speed bragging rights. Expect a maximum velocity in the 180 mph range. While all of the other vehicles in this gallery are available for sale right now, an on-sale date for the beautiful new Rapide will arrive early in 2010.