Tearaway's top speed tease

The Bugatti Veyron is the fastest production car in the world - so says British magazine Autocar.

The Volkswagen-owned supercar with its 747kW (1001bhp) W16 engine has been threatening to rewrite the record books since its launch in Europe last year.

Now in a pre-publication teaser to the motoring industry, the magazine says it is the first to measure exactly how quick the all-wheel-drive $2.5 million hypercar really is.

It attached timing gear to the Veyron and took it to VW's test facility in Germany, where its road test editor Adam Towler let the car's quad-turbocharged 8-litre engine loose. It produces peak power at 6000rpm and 1240Nm of torque at 2200rpm.

"I have never, ever felt acceleration like this," writes Towler. "Not in a plane, a train and certainly not in any automobile.

"The Bugatti catapults us from 50km/h to 80km/h in less than a second. A Lamborghini Gallardo requires two seconds, if you need a point of reference. After 2.8s we're past 100km/h. Then it dawns on me: the rate of acceleration is actually increasing."

The teaser doesn't say how fast Towler eventually went in the car. That will be revealed at a later date. But VW says it designed the Veyron to reach a top speed of 408km/h (250mph).

Top Gear's Jeremy Clarkson says he wound it up to 388km/h (240mph) before running out of road on an autobahn in Germany. He said at that speed it felt "totally and utterly rock steady".

VW mated two Audi V8 engines sharing a common crankshaft to make the W16. Then it added 10 radiators to keep things cool.

The engine drives all four wheels through a seven-speed direct shift gearbox gear (DSG) built by British engineering company and Formula One specialist Ricardo.

It's a beefed-up version of the six-speed DSG used in VW and Audi models in New Zealand.

Ricardo started work on the Veyron paddle-shift set-up in 1999. It took engineers many years and many millions of VW dollars before they were satisfied that the DSG could handle the Veyron's power.

But while the drivetrain got the power down without any problems, the shape of the bodyshell restricted the car's target speed in tests at the Sauber Formula One wind tunnel.

Sauber engineers could only simulate tests to 360km/h (220mph), the effective top speed in Formula One racing.

They told VW that for the Veyron to top 400km/h, its bodyshell had to be changed to improve aerodynamics. VW said no, that the shape of the supercar was set in stone.

VW then went ahead on its own. First it made the door mirrors smaller. But it found that wind turbulence at speed around the smaller mirrors upset the balance of the car at the front. The bigger mirrors worked better.

After much trial and error it hit upon the idea of a car that adapts to speed. The faster it goes, the more aerodynamic aids it produces.

At around 220km/h, electronics lower the front end by 5cm and a big spoiler pops up at the rear. Those who have driven it say they can feel the back of the car being pressed into the road.

These aids and the car's air-powered ceramic brakes help keep the Veyron out of the trees through to around 380-390km/h (234-240mph), a top speed similar to the three-seat McLaren F1 supercar.

That's its lot - until the driver stops the car and puts the ignition key in a slot in the door. Electronics lower the car still further and lock the rear spoiler into its place flush with the bodyshell. The result is a smooth teardrop-shaped tearaway that VW says is good for 408km/h - but only in a straight line, because without the aerodynamic aids its downforce has been reduced. Trying to nose the car at that speed through the slightest kink in the road would end in spectacular disaster.

At 408km/h, the Veyron is travelling at 112m - roughly from goalpost to goalpost at Eden Park - a second. But it takes 10 seconds and more than 500m to stop.

The Veyron EB 64 concept was on show in Auckland a few years ago.