If you have an ounce of gasoline in your veins, you know all about the Bugatti Veyron. You know it has a quad-turbo 16-cylinder engine that makes more than 1000 hp. You know it will accelerate to 60 mph in about 2.7 seconds, go faster than 250 mph, and costs well over a million bucks. You know the Veyron is the ultimate hypercar, that there is no fully street legal automobile in the world -- airbags and catalytic converters and all -- that is faster and more powerful.

You know it's one of the most extraordinary cars ever built.

VW Group chairman Ferdinand Piëch stunned the world when he announced the hyperbolic Veyron concept that had appeared at the 1999 Tokyo show would become a real production car. Equally stunned were the VW engineers, who were told in no uncertain terms by Piëch that the production Veyron would meet the preposterous power and performance targets he proposed. But the Veyron was almost a car too far, even for the visionary Piëch, the man who gave the world innovative machines such as the Porsche 917 and the original Audi Quattro, who reinvented Volkswagen, and who saved Bentley and Lamborghini from oblivion. Heat soak from the massive engine and high-speed stability were two major problems the engineers struggled to solve. Tires were a third. Michelin engineers simply laughed when their VW counterparts first asked for a tire capable of coping with the Veyron's mass and top speed: C'est impossible!

By late 2002, when Piëch retired from the day-to-day running of VW Group, it was clear the Veyron program was in trouble, and the car would miss its planned 2003 launch date. His replacement, Bernd Pischetsrieder, quickly cleaned house at Bugatti, installing talented VW transmission engineer Wolfgang Schreiber as the new chief engineer with a simple brief: Make the Veyron work.

And he did. When the 253-mph Veyron finally launched in 2005, Schreiber had delivered a benchmark supercar in terms of outright speed and performance. Then he upped the ante with the 1200-hp Super Sport version that reached 268 mph on the high-speed track at VW's giant Ehra-Lessien proving ground complex near Wolfsburg in 2010. Fittingly, after a stint running VW's commercial vehicles business, Wolfgang Schreiber is now CEO of Bugatti and Bentley, a man on the same fast track as his predecessor, Wolfgang Durheimer, who heads product development at Audi. The scuttlebutt around VW Group HQ is that one of these two men will one day run the company.

See all 7 photos

On a frigid April Saturday, Schreiber is standing in a small group huddled around a black-and-orange Bugatti Veyron Grand Sport Vitesse at Ehra-Lessien. It's a World Record Car edition Vitesse, one of eight that will be built at the tiny factory in Molsheim, France. You have to admire his chutzpah: The world record this car commemorates -- the fastest ever speed achieved by a production convertible -- hasn't actually been set yet, though the Bugatti boss has every reason to be confident it will be.

In simple terms, the Vitesse is a Veyron Grand Sport convertible that's been given the Super Sport treatment. In addition to 1200 hp at 6400 rpm, its 8.0-liter W-16 delivers a herculean 1106 lb-ft of torque from 3000 to 5000 rpm, courtesy of the same bigger turbos and intercoolers as the Super Sport, and, because you also need more fuel as well as more air to make more power, the same quad fuel pump setup. And boy does this thing have an appetite: Bugatti engineer Jens Schulenburg claims that at full throttle the Vitesse engine will consume more air in 1 hour than a human does in a month, though that statistic is purely academic because at full throttle the 1200-hp W-16 will gulp through an entire tank of gas -- 26.4 gallons -- in just 8 minutes.As you'd expect, the Grand Sport Vitesse is staggeringly fast. Bugatti claims a 0-60-mph time of less than 2.6 seconds and a quarter-mile time of 10.0 seconds. It says the Vitesse will reach 124 mph from a standstill in just 7.1 seconds and 186 mph in 16.0. What does that feel like? Like a Nissan GT-R on LSD. While the GT-R's acceleration to 100 mph is impressive, the Bugatti maintains the same relentless thrust way beyond 200 mph. Nail the gas in the Vitesse at 160 mph in fifth, and it responds like a regular Corvette or Porsche 911 might at 60 mph in third gear. It's truly, truly staggering. Especially for a car that weighs almost 4400 pounds.

The Vitesse alters the way you perceive the world. First will take you to 65 mph, second to 92, and third to 122, so the Bugatti will simply annihilate regular traffic, shrinking safe passing zones to absurdly small parcels of space and time. See a straight on any regular road, think of a number, and double it. That's the speed at which the Vitesse will be traveling when it arrives at the next corner. And that's no problem, because you simply hammer the carbon-ceramic brakes and the Vitesse stops. Just like that.

Removing the roof changes the way the air flows around the car, and that demands you pay attention to aerodynamic details in something as fast as a Veyron. The rear spoiler, for example, can detect whether the detachable hardtop is on or off the car, and so adjusts its angle of attack to ensure it delivers the same level of downforce at high speeds. Roof on, Bugatti says the Vitesse will hit 255 mph. Roof off, it's limited to a mere 233.

But not today.

The Veyron has three different drive modes. Standard mode is used for speeds up to 136 mph. Next comes Handling mode, where the adjustable suspension drops the nose of the car to improve its aerodynamic angle of attack and the massive rear spoiler is deployed to provide up to 770 pounds of downforce, or act as an airbrake. Handling mode will take you to 233 mph. If you want to go faster, you need Top-Speed mode, which can only be activated via a special key on the floor left of the driver's seat. This key unlocks the incredible high-wire act that takes the Veyron beyond 250 mph.

See all 7 photos

The problem is not power. The problem is the tires. To help them survive speeds beyond 233 mph, top-speed mode actually reduces the amount of downforce acting on the Veyron. The speed key therefore shuts the front diffuser flaps to provide a flat underbody, tucks the rear spoiler tight into the body, and drops the car lower to -- and level with -- the road. Because the Veyron is now way more sensitive to steering inputs and crosswinds, turning the steering wheel beyond a limited angle or touching the brakes automatically activates handling mode and reinstates the 233-mph limit. You have to stop and reset Top-Speed mode with the speed key.

Germany's unusually long and cold winter had already twice postponed the Vitesse record attempt, and Bugatti engineers delayed the start of today's run 30 minutes as the ambient temperatures struggled to climb above freezing in hazy sunlight. Schreiber says the cold, dense air increases aerodynamic drag and could reduce the top speed to below 250 mph.

Even so, Chinese part-time racer and full-time entrepreneur Anthony Liu (he has a $2.6 million Grand Sport Vitesse

of his own on order) effortlessly nails 254.04 mph with just one pass down the 5-mile straight, and the speed is confirmed by the German technical inspection and certification organization, the TUV.

And just like that, the Bugatti Veyron Grand Sport Vitesse is officially the world's fastest convertible.

How Fast Can a Veyron Go?

Former F1 racer Pierre-Henri Raphanel, Bugatti's official test driver and one of the world's bravest men, says the only thing preventing the Veyron from going beyond 270 mph is tire technology.

Raphanel, who's probably spent more time on the far side of 250 mph than any driver in history, says tires were the major concern during his record-breaking 268-mph run in the Veyron Super Sport at Ehra-Lessien in July 2010. VW engineers told him they thought the tires should be fine. But they couldn't be sure. In testing Michelin had run the Veyron's massive meats on its tire dyno at 270 mph -- the fastest it can spin -- for 20 seconds, then at 250 mph for 20 seconds. It repeated that cycle two more times. Then the tires exploded.

Heat, mass, and centri-fugal force will eventually destroy even the best-built tires. The Veyron's Michelins, which cost $42,000 a set, take 1 hour per tire to make. And Michelin will only allow two sets of tires to be fitted before the rims, which cost $69,000 a set, also have to be replaced to ensure the integrity of the bead seal at high speed.

Bugatti engineer Jens Schulenberg says getting more than 1200 hp out of the Veyron's W-16 isn't difficult. "We could go faster," he admits. Rumors are swirling of a 1600-hp SuperVeyron that will be 500 pounds lighter with a projected top speed of 288 mph. All it needs is the right tires.