Super-high speed
"A perfect balance between drag coefficient and downforce is essential at very high speed," says Schreiber. "Before you can attempt to reach the 254-mph top speed, the car's aerodynamic profile needs to be adjusted." To do so, you turn the "speed key" located between seat and sill. In top-speed mode, the rear wing and the tail spoiler above it retract almost fully, the front diffuser panels close, the ride height drops to 2.6 inches at the front and 2.8 inches at the back, and the drag coefficient decreases from 0.37 to 0.36. In this setup, drag is at a minimum--but so is downforce. At the front, there is zero lift, and at the rear, there is a mere 88 pounds of downforce.
In handling mode, which is good for up to 233 mph, the corresponding figures are 331 pounds on the front axle and 441 pounds on the rear end. Like the Mercedes-Benz SLR McLaren, the Veyron is equipped with an air brake. In the Bugatti, however, rear visibility remains intact even when the flap is up. "When you hit the pedal hard at 126 mph plus, the air brake gives 0.6 g of additional deceleration. At the same time, the downforce increases by up to 662 pounds. As a result, the rear wheels can brake harder without approaching lockup," says the chief engineer.
Team Bugatti spent many days in the wind tunnel to fine-tune the Veyron for the best blend of speed, thermodynamics, and stability. Although the quoted power output is 987 hp, all the engines built so far have made 1035 hp.
Cooling a cannonball
"It's impossible to completely cool down this amount of energy," says Schreiber. "But you can implement stringent airflow management to increase the amount of air to the engine." The Veyron has four heat exchangers: two big ones in the nose of the car, for the engine and for the intake air, as well as two mid-size. Two more air-conditioning condensers are positioned in the wheelhouses. When needed, up to four fans expel excessive heat.
"It is extremely difficult to find a common denominator for the cooling and aero requirements," acknowledges Schreiber. "With every extra cubic inch of air that flows through the car, the coefficient of drag suffers, and you lose a little speed. That's why several of the vents you saw on the show car had to disappear." To stop the front brakes from frying the pads under pressure, the steering knuckles feature integrated snail-shaped ducts that lead cool air to the discs.
In stop-and-go traffic, all air deflectors automatically go into maximum cool-down mode. At this juncture, the complex steel and aluminum architecture sizzles and crackles like a swarm of locusts, and the car is engulfed by the scent of hot engine oil, burnt fuel, brake-pad dust, and Michelin rubber.
The ultimate suspension compromise
According to Schreiber, "The Veyron covers a wider speed spectrum than any other sports car. It must ride reasonably well at 25 mph, and at the same time, it must be perfectly stable and confidence-inspiring at 250 mph. To meet these conflicting requirements, there are three different suspension settings: standard, handling, and top speed. Instead of installing adjustable springs, dampers, and antiroll bars, we opted for a quick-acting central hydraulic system that permits, among other things, instantaneous ride-height adjustments."
In standard mode, the ground clearance is 4.9 inches all around--enough to climb curbs and straddle traffic-calming speed bumps. The Bugatti runs on OZ wheels shod with run-flat PAX tires supplied by Michelin. The sizes read like credit card numbers: 265-680/R-500A up front, 365-710/R-540A out back. The chassis incorporates an ambitious mix of high-tech elements (see Techtonics sidebar).
The Bugatti boys certainly got their calculations right. Even at very high speeds, the roadholding is simply phenomenal, and the car is incredibly stable. It tracks with precision through fast or slow corners, and things like traction or lift-off oversteer are never an issue. Bugatti fitted four-wheel drive to ensure optimum stability in all conditions, with a dynamic torque split that typically sends 70 or 80 percent of the torque to the rear wheels, which are governed by an electronic diff lock. The steering is quite direct at two turns from lock to lock, but at the same time, it feels totally relaxed. As you might expect, in a car designed to run at 250 mph, the brakes are phenomenal--as we prove several times when slow-moving traffic fails to spot us. ...next page >>