Bugatti is close to signing off on the most extreme version of their Chiron. The Pur Sport has been in development for over a year and a half, and is currently in the final stages of engineering testing. When all is finalized, it will be released to the market at a price of around US$3,599,000. The work being performed is intense and precise. Areas of focus involve the chassis itself, tweaks to the transmission and already potent W16 engine, plus the wheels and tires. Let’s take a look at what’s going on.
The engineers have been working diligently with Michelin to develop bespoke rubber for the Chiron Pur Sport. After exhaustive testing, Michelin’s Sport Cup 2 R tires were chosen and there is a prodigious grip thanks to the compound and the sheer size. The front has 285/30 R20 whilst the massive rears, 355/25 R21, will ensure that the Bugatti Chiron Pur Sport will hang on at high velocities, especially in corners thanks to a ten percent increase in lateral acceleration. A newly developed structure and a softer compound were part of the solution, with that compound also tuned to work with the changes to the chassis.
Magnesium is renowned for its strength and lightness, making the choice of the material for the wheels a simple one. Bugatti also offers optional “Aero” blades that optimize air extraction from the wheel arches. Aerodynamics are simultaneously improved. Also, whilst the Bugatti Chiron Pur Sport is underway, the blades pull air through the wheel and add to the downforce. A cover was designed to both visually finish the wheel and to reduce turbulence around the wheel nut indentations.
Each wheel on the Bugatti Chiron Pur Sport is rated as 8.8 pounds lighter than the previous versions used, meaning a total weight reduction of just over 35 pounds has been achieved. By reducing the mass of the wheels, the unsprung mass, it means that the suspension can react quicker to changing road conditions. Jachin Schwalbe, Head of Chassis Development at Bugatti, said “This increases traction because the wheel can be kept on the ground more effectively. Every driver will feel a sense of lightness in corners.”
It’s within the chassis that the intense and minute scrutiny of the underpinnings, says Schwalbe, will pay off. For example, the axles have had their camber changed (now minus 2.5 degrees) to extract more performance and stability. However, this brought a need to develop new suspension joints in order to allow that change. Supercomputing was used to calculate which of 17 possible final variations would be used to work with the other tweaks and changes.
New springs were developed and are tauter than before. The front has springs rated at 166 N/mm at the front whilst the rear has 200 N/mm, instead of 100 N/mm at the front and 150 N/mm at the rear. It’s a firmer setup yet ride quality is not sacrificed. Schwalbe says, with classic understatement: “It took us many, many test kilometers to arrive at this conclusion.”
Such is the precision being engineered in, the real-time adjustments for the shock absorbers are less than six milliseconds elapsed time between the measurement and force adjustment. Stiffer bearings for the spring struts improve the steering response and handling, with the new connection points rated at 2.3 times stiffer upfront and 1.7 times stiffer at the rear. Schwalbe says: “More than 50,000 test kilometers are required for chassis fine-tuning alone!”
The Engine And Transmission. Peak power is 1,479hp and that’s on tap between 6,700 and 6,900 rpm, a range that has the peak power coming in just 200rpm higher than the engine in the Chiron. The maximum engine speed is now 7,000 rpm. The 8.0L W16 has a peak torque output of 1,500Nm or 1,180 ft-ld. Each of the ratios in the seven-speed automatic has been “shortened” by 15%, meaning off-the-line and rolling acceleration is quicker. There’s been a tenth shaved off the 0-62mph time, down to 2.3 seconds. The 0-125mph time is also quicker, down from 6.1 seconds to 5.9. Part of the increases in speed changes comes from the engineers returning the wastegate valves for boost pressure control.
Moreover, the Bugatti Chiron Pur Sport accelerates in sixth gear from 37mph to 74.5mph in 4.4 seconds instead of 7.4. The vehicle’s top speed is now electronically regulated at 217.5mph, with a maximum shift speed of 6,900 rpm. This area came under scrutiny too, with more precise matching of the shift points to the engine’s revs to ensure a smoother transition between ratios. Carl Heilenkötter, the transmission development engineer at Bugatti, explains: “We spent one and half years developing the control system so as to ensure that every shift really does fit exactly in all driving conditions. First in simulation, then on the test stand and finally on the test and circuit tracks as well as on country roads and motorways.”
The Summation. Christian Willmann, the engineer responsible for driving dynamics slip control systems and all-wheel drive at Bugatti sums up the process. “The Chiron Pur Sport is not just sporty and safe on race tracks but on public roads in day-to-day driving, too.”
The Bugatti Chiron Pur Sport is a hyper sports car consistently calibrated for agility and performance with deliveries currently scheduled for the second half of 2020.