Anatomy of a Supercar: Bugatti Veyron

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Anatomy of a Supercar: Bugatti Veyron

By Steve Sutcliffe, roadandtrack.com

Bugatti Veyron, fastest production car in the world

Bugatti Veyron, fastest production car in the world

Bugatti Veyron

supercar

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The Bugatti Veyron 16.4 is no doubt the result of many thousands of engineering hours, and certain elements of the car are indeed cutting-edge concept and design. The two main

The Bugatti Veyron 16.4 is no doubt the result of many thousands of engineering hours, and certain elements of the car are indeed cutting-edge concept and design. The two main areas that demonstrate new technology are the engine and the transmission.

The engine itself is an engineering wonder and includes some interesting new anti-knock sensing. The gearbox and gear-change system are right up to date utilizing dual-wet clutches and twin layshafts. In my opinion, this is the only way to go to attain quick, smooth gearchanges for a vehicle without a manual clutch. Most semiautomatic systems are violent in their application and not very satisfying from a driver's point of view. The Veyron gearchange is fast and extremely well applied. The complete powertrain is a great showcase for the parent company, Volkswagen AG. Another area where the car is pushing boundaries is with its electronic control systems and, in particular, their application. I drove the Bugatti on the road and on the track, which demonstrated just how seamlessly the chassis and powertrain functions have been sewn together.

The chassis/body structure is hybrid like the last Bugatti (EB110) with carbon fiber used for the primary structure and aluminum alloy for the body and front crash structure. In this respect, the all-carbon McLaren F1 and the RTM (Resin Transfer Molding) carbon Mercedes-Benz SLR McLaren are, in fact, more advanced. Carbon-ceramic brakes are used as with the Porsche GT and the SLR.

The aerodynamics is interesting and complex. The design and development have been directed at problem-solving in the areas of cooling and vehicle stability. At such high speeds, the basic shape of the Veyron will generate a lot of lift. Add to this a large frontal area and 10 radiators and heat exchangers, and suddenly here's where the 1001 hp [metric horsepower] dissipates at 250 mph! The CDA figure [drag coefficient x frontal area] is at the high end of the scale for rear-engine sports cars. At these sorts of speeds, a massive amount (often three or four times the net figure) of downforce has to be generated to overcome the basic lift in order to achieve the target figure for net downforce. The Veyron is a full ground-effect vehicle like the McLaren F1 and Ferrari Enzo. The downforce increases as a square of the speed, so there are large forces to design for at speeds approaching V max [top speed] these forces eat into available suspension travel and can cause high-speed stability problems.

Compounding this problem is that ground-effect cars are notoriously sensitive to ride height and pitch changes. I solved these problems on the F1 by having just enough downforce for high-speed stability and by giving the driver a manual control over the rear wing for a 50-percent increase in downforce at lower speeds. The F1 is also designed with an automatic "air brake," which deploys when the chassis ECU detects a certain combination of speed and deceleration. The air brake increases the CD but more important, interacts with the ground-effect forces by increasing the tail vortex and base suction, which results in an increase in downforce of 100 percent and a rearward movement of the aerodynamic center of pressure of about 4 ft., which helps negate the pitch problem. The Veyron uses the McLaren air brake system but also has a hydraulic ride-height control system, which optimizes the ride heights and chassis incidence for different speeds and loads. The F1 goes a little further with automatic brake cooling and fan-assisted boundary control for the rear diffuser.

When designing a car, I like to do a large amount of aerodynamic "block studies" this being the basic size of the car with a cabin shape derived from engineering and packaging studies. The block model incorporates representative internal airflow for cooling. This process determines air entry and exit holes, along with the basic shape of the car so styling can begin.

As the drag increases as a square of the speed, the power requirement increases as a cube of the speed because the power itself is speed-dependent. The Veyron because of its high CDA figure and huge cooling drag needs 1001 hp to go 12 mph faster than a McLaren F1 producing 627 hp. To help understand the problem of starting a car program from a weak point aerodynamically, we do some calculations: A turbocharged F1 producing 1001 hp would achieve 281 mph assuming the same drivetrain efficiency. Another way of looking at this equation is that an F1 would need "only" 740 hp to reach the Bugatti's top speed. All this demonstrates just what an uphill struggle the Bugatti team faced to achieve their targets.

Very high top speeds in road cars produce some other very challenging problems. Some are small, such as keeping the windshield wipers attached to the glass, preventing the centrifugal force from opening the tire inflation valves and making the side mirror mounts torsionally stiff enough not to rotate at V max. Then there are much more serious high-speed problems such as a partially open side window being sucked out from the very low local pressure caused by the air accelerating around the A-pillar. Tire designers can design for very heavy vehicles or very high speeds but a combination of the two is a massive challenge. A Bugatti Veyron fully loaded and with aerodynamic load is in the order of 2 tons at 250 mph!

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