"Shaped by Speed" - through technical superlatives to the fastest and most luxurious Grand Tourisme in the world

Reading time 11 Min.

In August 2019, the Chiron Super Sport 300+ was the first production car to break the 300-mile barrier. Since then, at 304,773 mph (490,484 km / h), it has been considered the fastest production vehicle in the world. A technological masterpiece and a record that has not been broken so far. With the Chiron Super Sport2, Bugatti offers extreme longitudinal dynamics and a pole of maximum spread of the "Bugatti Spectrum of Performance". In order to reach a top speed of 440 km / h, it is not enough just to increase performance. Rather, some profound technical changes to the body, engine and chassis were necessary in order to be able to drive safely and reliably at such extreme speeds. With dedication to detail and the pursuit of technical perfection, the Bugatti engineers developed a groundbreaking hyper sports car.

Optimized aerodynamics

A top speed of over 400 km / h not only requires a powerful drive, but also the lowest possible aerodynamic drag. With the Bugatti Chiron Super Sport, engineers and designers spent months tinkering with the best aero balance, the lowest air resistance and the greatest possible downforce.

New air curtains

For speeds above 400 km / h, balanced and safe driving behavior is crucial. "Only if the flow towards the body is perfect at the front will disturbing turbulence remain low and the air will flow cleanly around the body," says Frank Heyl, Deputy Design Director at Bugatti. In order to minimize the turbulence on the side as well as possible, the team integrated newly developed air curtains at the front - two wing-like profiles - which guide the air optimally around the corner.

At the same time, the air curtains ensure that the air flows tightly along the body for as long as possible, thereby stabilizing the vehicle. This reduces pressure losses and resistance - the ideal outer skin for fast driving "Shaped by Speed". In order to achieve the perfect flow around, the experts worked in countless simulation loops on the ideal curvature and strength of the component as well as the best distance to the main volume of the front. Additional outlets on the front wheel arches help to further balance the aero loads.

Flow through the front end

An ideal flow of air through the front end of the vehicle is just as important for a balanced balance at high speeds. The ideal amount of air must flow through the radiator in order to provide sufficient cooling air for the 8,0 W16 engine at full load. The air mass flow through the water cooler is around 8 percent higher in the Chiron Super Sport than in the Chiron, in order to guarantee a thermally perfect air balance. In addition, a large part of the high mass flow flows through the new air curtains at a high exit speed. In top speed mode, the front diffusers are flatter and direct less air into the wheel arches.

New developed fenders

The nine air outlets on the front fenders stylistically cite the super sports car of the 1990s, the Bugatti EB 110. As a super sports variant, Bugatti built the EB 110 between 1993 and 1995, relying on lightweight construction, performance, luxury and exclusivity. It will be the first super sports car with a carbon fiber body, all-wheel drive and four turbochargers. The V12 turbo develops over 610 hp and sets several records with the EB 110 Super Sport, including the one for the top speed of 351 km / h. In the EB 110 SS, five cylindrical air inlets help ventilate the engine compartment. In the Chiron Super Sport, the front wheel arches are ventilated through nine cylindrical air outlets.

Thanks to Computed Fluid Dynamics (CFD) simulations, the experts calculated the exact air throughput in order to create the perfect aerobalance. With the cylindrical air outlets, Bugatti prevents the dynamic pressure in the wheel arches from lifting the front of the Chiron Super Sport. This component generates downforce without generating additional drag - as would be the case with an additional spoiler. Nominally, these vents generate around 20 to 30 kilograms of additional downforce at 380km / h and thus help to bring the balance of the downforce into equilibrium.

New aero function for wheel arch ventilation

The nine cylindrical air outlets protrude about 30 millimeters down through the fender and are connected to the wheel house by a special carbon air guide. This ensures optimal outflow and prevents stones from escaping through the ventilation. At the same time, the new fenders support better brake cooling. As with a chimney, a negative pressure from the current flowing past the body pulls the air out of the wheel arches. In addition, the air is sucked out of the wheelhouses through special ventilation ducts behind the front wheels. Stylistically, these elements are arranged behind the front wheels like gills.

Fenders are handcrafted

The fenders, which weigh around four kilograms, are handcrafted from exposed carbon, with the fibers running over the edges. Each of the nine cylindrical vents is a different size. For aesthetic reasons, the visible radii are identical. In addition, the newly developed fenders meet safety regulations for pedestrian and impact protection worldwide. To do this, the very stiff construction is weakened at certain points in order to absorb energy. This allows the fenders to deform at low speeds in the event of a collision, but remain extremely stiff at high speeds.

Long tail for high speed

When you first look at the Chiron Super Sport, you notice the 23 centimeter-longer rear, the so-called longtail. At high speeds, it ensures that the air flowing above and below the vehicle reaches the smallest possible separation area at the rear. In order to achieve a balance between downforce and lift forces, Bugatti precisely coordinates the rear wing and diffuser, among other things. To do this, Bugatti has enlarged the cross-section of the diffuser. This moves the separation edge of the diffuser further upwards, so that the separation area at the rear is minimized. This significantly reduces the losses occurring there and thus the wind resistance - because it brakes a vehicle.

Larger rear wing

In handling mode, the wing blade of the rear wing, which has been extended by 23 millimeters and is therefore 8 percent larger, in conjunction with the larger diffuser creates a significantly improved effect of the air brake. In top speed mode, on the other hand, the rear wing retracts almost completely: This means that the long-tail concept comes into its own and the laminar flow can fit neatly against the body over the full length of the outer skin until it breaks off in a defined manner at the rear. This significantly reduces the resistance.

"In top-speed mode, the Chiron Super Sport generates minimal resistance, so it is perfectly balanced and as aerodynamically efficient as technically possible," says Frank Heyl. The aim was to keep downforce and lift exactly in balance at speeds above 400 km / h. “Super Sport generates just enough downforce to be neutral beyond 400 km / h. In terms of speed, this is essential in order not to overload the tires, ”continues Frank Heyl. At these speeds the lift is immense, so that the Chiron Super Sport has to generate considerable downforce in order to neutralize these forces.

Larger diffuser

Bugatti redesigned the diffuser under the Chiron Super Sport in order to generate as little resistance and high driving stability as possible at speeds above 400 km / h. The extended stern increases the length of the diffuser by around 23 centimeters. In order to increase the effect of the diffuser and to give it more space, Bugatti has moved the exhaust system, which is otherwise in the middle, to the sides, one on top of the other. The two tailpipes are positioned one on top of the other in order to reduce the effective area of ​​the diffuser as little as possible. This increases the total area of ​​the diffuser by 32 percent compared to the Chiron. "In addition, there is the most efficient area, the middle, free for an undisturbed flow for the best effect," says Christoph Dobriloff, aerodynamics development engineer at Bugatti.

Exhaust system in titanium 3-D printing

The two exhaust gas covers represent a special feature. Using 3D titanium printing, an extremely thin double-walled structure is created, some with a wall thickness of only 0,4 millimeters and thus close to the limit of what is technically feasible. A lattice structure gives the component stability, which also offers space for airflow channels.

Due to the double wall, the titanium exhaust screen has an insulating effect, while the air flow around it reduces the temperature of the exhaust screen. To protect the surrounding carbon parts from excessive heat, the Chiron Super Sport has additional air inlets in the underbody. The cool fresh air blows in a ring around the exhaust gas-carrying geometries from the tailpipe trims. As a result, the exhaust gas, which is up to 850 degrees Celsius, flows in a jacket of cold air. This prevents the hot exhaust gases from hitting the stern back. "Even at full load and at top speed, the exhaust gases do not affect any components and prevent backflows," says Jens Wenge, design engineer at Bugatti. Titanium itself only reaches its melting point at 1.668 degrees Celsius. Further advantages of the titanium print: precise edges, minimal joints and therefore better flows as well as minimal post-treatment. After the 3-D printing, the exhaust cover is only blasted and then cleaned with compressed air. It can be painted black on request. In addition, a 3-D printed titanium component weighs 930 grams, a good 570 grams, around a third less than a component made from investment casting.

W16 drive with more power and higher rated speed

In order to reach the top speed of 440 km / h, Bugatti increases the maximum output of the 8,0 W16 drive to 1.177 kW / 1.600 PS - an increase of 100 PS. For more agility, the drive turns 300 revolutions per minute higher, now to a nominal power plateau of 7.050 to 7.100 revolutions per minute. 1.600 Newton meters of torque are now from 2.250 to 7.000 revolutions instead of the previous 6.000 revolutions. The engineers developed many new components to improve performance: for example, stronger pistons transmit the power of the 16 cylinders, and thanks to a harder pressure control spring with a higher oil pressure, the oil pump now delivers more lubricant to the individual points such as the crankshaft, valve and chain drive, camshaft adjustment and piston cooling. More than 140 liters per minute flow through the pump at full load and rated speed.

The increase in performance and the higher speeds lead to an increase in vibration excitations, which put more stress on the chain drive and the valve train with the four camshafts and 64 valves. To ensure durability at maximum engine speed, Bugatti is redesigning the bearing pin of the chain tensioning rail and has to adapt the cylinder head to do this. Modified valve springs on steel spring pads can now safely withstand the higher loads. In order to meet current legal acoustic requirements, new multi-layer GRP acoustic chain boxes reduce noise emissions. A modified torsional vibration damper on the crankshaft, which is mounted on the belt drive side, ensures that the engine runs particularly smoothly. Bugatti also adapts the auxiliary unit drive with generator, air conditioning compressor, water pump and tandem pump to the higher speed.

More efficient turbochargers

In addition to the increase in speed, the increased performance results from optimized and newly developed turbochargers. The four turbos now have a compressor wheel enlarged from 74 millimeters to 77 millimeters in order to be able to achieve the higher mass flows. The diameter of the turbine wheel grows from 64,4 to 67,2 millimeters in order to be able to provide the compressor drive power required for the high boost pressure. At full load, 4,8 tons of air per hour flow through the four chargers. Optimizing the blade geometry increases the thermodynamic efficiency, and the response behavior is almost the same as that of the Chiron. "Despite the increased output, the weight of the engine does not increase and the response behavior of the turbocharger remains at the good level of the 1.500 hp engine," says Andreas Kurowski, engine development engineer at Bugatti.

Gearbox with new translation

In order to reach the top speed of 440 km / h, the seven-speed dual clutch transmission has been given a new gear ratio. Seventh gear is translated 3,6 percent longer than in the Chiron. Due to the increased output, the seven-speed dual clutch transmission only shifts from sixth to seventh gear under full load and full acceleration at 403 km / h. The Chiron Super Sport accelerates from 0 to 200 km / h in 5,8 seconds and to 300 km / h in 12,1 seconds. The difference between sprinting from standstill to 400 km / h is even greater: the Chiron Super Sport reaches that speed in just 28,6 seconds. It drives 12 percent faster, or a full 4 seconds, than a Chiron. So that the occupants do not feel this interruption in tractive power when shifting gears, the boost pressure control in the gears is set even more finely. The acceleration does not stop even from 6.000 revolutions and gives the Chiron Super Sport a huge boost up to 7.100 revolutions.

Newly developed and tuned chassis

Bugatti is redeveloping the chassis of the Chiron Super Sport especially for high speed and the new aerodynamics. The engineers have increased the spring rate on the rear axle by seven percent compared to the Chiron in order to further stabilize the Chiron Super Sport at speeds above 420 km / h. “The longtail results in a different axle load distribution, which we took into account when tuning the chassis,” says Jachin Schwalbe, Head of Chassis Development at Bugatti. In conjunction with the longer rear and the modified front, the Chiron Super Sport achieves a balanced aerobalance at high speed. To do this, the engineers re-tune the electronically controlled chassis and adapt the philosophy for damping vehicle movement to match the genes of Super Sport. As if in real time, it regulates the damper settings within six milliseconds and adapts to vehicle movements.

New Michelin tires for top speed

Newly developed Pilot Sport Cup 2 tires from Michelin, optimized for top speed, offer more rigidity and smoothness at speeds of over 420 km / h than the Chiron. In addition, they are the only tires that have been tested at speeds over 500 km / h. It is made possible by a new technology with reinforced belt layers that cope with enormous forces - tested on a test stand that was originally built for jet aircraft. After production, each tire in the dimension 285/30 R20 ZR at the front and 355/25 R21 ZR at the rear is individually x-rayed in order to rule out even the smallest irregularities. The Michelin Pilot Sport Cup 2 tires are designed for extreme longitudinal dynamics and thus support the philosophy of the Bugatti Chiron Super Sport.

Light rims in a new design

To further reduce the unsprung mass, Bugatti is developing new five-spoke aluminum rims that weigh four kilograms less per wheel set than the wheels of the Chiron. In addition, they provide even more rigidity for longitudinal dynamics and are therefore ideally suited to the Chiron Super Sport. Bugatti optionally offers a magnesium wheel set that weighs 16 kilograms less than the Chiron and thus further reduces the unsprung mass on the axles.

With the Chiron Super Sport, Bugatti is developing a hyper sports car of extremes. With many technical changes and the pursuit of perfection, the fastest production vehicle is created with its very own character, extraordinary design and unmatched level of luxurious comfort. Bugatti manufactures the Chiron Super Sport at the brand's headquarters in Molsheim. The first vehicles will be delivered to their new owners at 3,2 million euros (net) each at the beginning of 2022.

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"Shaped by Speed" - through technical superlatives to the fastest and most luxurious Grand Tourisme in the world
Photo credit: Bugatti

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