Bugatti Chiron breaks 300mph barrier

English racing driver Andy Wallace has hammered a modified Bugatti Chiron Sport to beyond 490km/h over the weekend.

The 8.0-litre quad-turbo W16 hypercar whipped into uncharted territory, beyond 300mph, with a 490.484km/h (304.77mph) single-direction top speed on the Volkswagen Group’s Ehra-Lessien test track in Germany.

The updated 'longtail' version of the standard Chiron Sport, which will soon enter production as a limited-edition high-performance variant, included a taller top gear, a stronger occupant safety cell and some aerodynamic tweaks including a smaller fixed wing to replace the active unit and a longer rear diffuser, extending the vehicle's length by 25mm to 4.79m.

The mighty engine also received a few tweaks, moving up almost 100 horsepower from the standard model’s 1120kW (to 1176kW), helping add an astonishing 70km/h to the Chiron’s top speed.

Although it does not stand as a top-speed record because it was recorded only in one direction, Germany’s Technical Inspection Association verified the run, which easily trumps similar one-way speed records by the Koenigsegg Agera RS (284.55mph or 457.9km/h) and Hennessey Venom GT (270.49mph or 435.3km/h).

"What a record! We're overjoyed to be the first manufacturer ever to have achieved a speed of more than 300 miles per hour,” said Bugatti president Stephan Winkelmann, who has previously claimed the Chiron will one day crack 500km/h.

“It’s a milestone for eternity. I would like to thank the whole team and driver Andy Wallace for this outstanding performance,” he said.

The run was so fast that the car’s telemetry to the garage couldn’t keep up with it, with Wallace’s GPS display showing him 490km/h, but the pit area showing just (!) 479km/h. The top speed record was confirmed from the on-board data.

Bugatti doesn’t plan to attack an even faster record, with Winkelmann believing the milestone of first past the 300mph barrier to be worth more to the brand than another few km/h.

“We have shown several times that we built the fastest cars in the world,” he insisted.

“In future we will focus on other areas. Bugatti was the first to exceed 300mph – its name will go down in the history books and it will stay that way forever.”

It’s not the 58-year-old Wallace’s first time as a production-car record breaker, with the Le Mans winner smashing records in both the McLaren F1 and Jaguar’s XJ220.

The record came at the end of a four-day assault on the 20km high-speed loop of Ehra-Lessien, Volkswagen’s top-secret test track, which features an 8.7km perfectly flat straight.

All of the Veyron’s top speeds were set at the same track, including the original 407km limited V-max of the original car, while a Veyron Super Sport hit 431km/h there in 2010.

The details that went into the record attempt were astonishing, with Bugatti repeatedly X-raying each Michelin Pilot Cup 2 tyre and every forged alloy wheel before every run, because they had to rotate at 4100 revs per minute at top speed.

There was also the slight surprise to Wallace of the gyroscope effect from the wheels at very high speeds.

“At 200mph you can barely feel it, but at 300mph it’s absolutely enormous,” the driver told an Autocar journalist at the track.

“It’s felt mostly on the front wheels and therefore the steering, like a spinning top when it starts to move it wants to continue to move.”

There was also some guesswork on the aerodynamic kit, designed by Italian racecar manufacturer, Dallara, to have zero lift and an aerodynamically neutral balance at high speed. But no wind tunnel could test it at those speed before the live runs.

"But it doesn’t mean the air is having no effect, there’s close to 2000kg on the top surface of the body trying to pick the car off the ground and another 2000kg under the car trying to pull it back down – two fighting forces that come to four tonnes roughly… So you’ve got to be absolutely sure that everything on the car is secure enough to go this fast,” Wallace said.