In August 2019, it became the first production car to break the 300-mile limit. It is considered the fastest production car in the world at 304.773 mph (490.484 km/h). Bugatti offers extreme longitudinal dynamics and maximum bandwidth in the “Bugatti Performance Spectrum”.
Reaching a top speed of 440 km/h isn’t just a matter of improving performance. Extensive modifications to the body, engine and chassis are required to ensure safe, comfortable and reliable driving at such extreme speeds – the French luxury automaker’s forte. With a love of detail and a quest for technical perfection, Bugatti engineers have developed a groundbreaking supercar.
Optimized Aerodynamics
A top speed in excess of 400 km/h requires not only a powerful engine, but also very low air resistance. Bugatti engineers and designers spent months finding the optimal aerodynamic balance for the Chiron Super Sport for the lowest drag coefficient and maximum downforce.
New Air Curtains
Above 400 km/h, balanced and safe driving behaviour is critical. “Only perfect airflow at the front of the vehicle can avoid harmful turbulence and ensure that the airflow around the car remains clean,” said Bugatti Deputy Design Director Frank Hale.
To minimise lateral turbulence, the team employed a newly developed air curtain at the front, similar to a wing that helps guide air optimally around corners. At the same time, the air curtain also ensures that the airflow follows the contours of the body as precisely as possible to stabilize the car. This reduces pressure loss and drag – the ideal skin for fast driving “speed shaping”. To achieve perfect airflow, Bugatti engineers ran numerous simulations to determine the ideal curvature and thickness of the component, as well as the perfect distance between it and the front end. Additional air outlets on the front wheel arches help to further balance the air load.
Air Flow through the Front Section
Equally important for balanced handling at high speeds is optimal airflow at the front of the vehicle. The optimal amount of air must flow through the cooler so that it can adequately cool the 8.0-liter W16 engine at full load. Airflow through the Chiron Super Sport radiator is approximately 8% higher than that of the Chiron to ensure perfect air balance. In addition, most of the airflow passes through the fresh air curtain at high speed. In extreme mode, the front diffuser is more horizontal, directing less air into the wheel arches.
Newly Developed Wings
Nine air vents on the front fenders recall the style of the legendary Bugatti EB 110 supercar of the 1990s. Bugatti built the EB 110 between 1993 and 1995 as a super sports model based on lightweight construction, dynamic principles, luxury and exclusivity. It was the first supercar to feature a carbon fiber body, all-wheel drive and four turbos. The V12 turbo produced more than 610 horsepower, enabling the EB 110 Super Sport to set several records, including a top speed of 351 km/h. The EB 110 SS features five cylindrical air intakes that provide proper airflow to the engine compartment. The front wheel arches of the Chiron Super Sport also feature nine cylindrical air outlets. Using computational fluid dynamics (CFD) simulations, experts are able to calculate accurate airflow rates for perfect air balance. By using cylindrical air vents, Bugatti avoided a situation where dynamic pressure in the wheel arches of the Chiron Super Sport would raise the front of the car. As a result, this component creates downforce without adding additional drag, as is the case with the addition of a spoiler. At 380 km/h, these outlets generate around 20 to 30 kg of additional downforce, helping to balance all sources of downforce.
New Wheel Arch Ventilation Function
The nine cylindrical vents are 30mm deep fender penetration holes, connected to the corresponding wheel arches by special carbon air ducts, ensuring optimal airflow while preventing rocks from leaving the car. Meanwhile, new wings have improved brake cooling. Similar to a chimney, the vacuum created by the airflow along the car body draws air out of the wheel wells. In addition, air is channeled through special ventilation ducts and drawn out of the cab behind the front wheels. Stylistically, these elements are placed behind the front wheels like gills.
Handmade Wings
The wing weighs around four kilograms and is handcrafted from clear-coated carbon with fibre around the edges. Each of the nine cylindrical vents is a different size. For aesthetic reasons, the visible openings are the same. In addition, the newly developed wing complies with global pedestrian and crash protection safety regulations. For this, very rigid structures are weakened at certain points to absorb energy. This allows the wing to deform in slow impacts while remaining extremely stiff at high speeds.
A Longtail for High Speeds
The first thing you notice about the Chiron Super Sport is the 25cm-long rear, which is known as the long tail. At high speeds, it ensures that the air flowing over and under the vehicle creates the smallest possible tearing surface. To strike a balance between downforce and lift, Bugatti precisely matched the performance of the rear wing and diffuser by increasing the diffuser profile. This will move the tear-off edge up, minimizing the tear-off area of the tail. This significantly reduces the losses generated in this area, which greatly reduces drag – and thus slows down the car.
Larger Rear Wing
In handling mode, the blades of the rear wing are 23mm longer, and therefore 8% larger, which, combined with the larger diffuser, makes the airbrake significantly more efficient. But in extreme speed mode, the rear wing retracts almost completely, allowing the car to fully demonstrate its long tail design concept. This way, laminar flow can build up over the entire length of the body until it breaks at a specific point in the rear. This significantly reduces air resistance.
“In top-speed mode, the Chiron Super Sport generates only minimal resistance, making it perfectly balanced and as aerodynamically efficient as possible,” says Frank Heyl. The goal was to perfectly balance downforce and lift at speeds above 400 km/h. “The Super Sport generates just enough downforce to stay stable above 400 km/h. That’s essential at this speed to avoid putting excessive pressure on the tires,” Frank Heyl continues. At these speeds, lift is enormous, meaning the Chiron Super Sport has to neutralize it by creating considerable downforce.
Larger Diffusor
In order to generate the least possible drag and stabilize the car at speeds in excess of 400 km/h, Bugatti also had to redesign the diffuser at the bottom of the Chiron Super Sport. Due to the lengthening of the rear, the length of the diffuser has increased by approximately 23mm. To increase the efficiency of the diffuser and give it more space, Bugatti moved the exhaust section from the center to the sides. The two exhaust pipes are arranged one above the other in order to minimize the effective area of the diffuser. “Furthermore, the most efficient area, the middle, is the unobstructed airflow and the best results,” said Christoph Dobriloff, aerodynamic development engineer at Bugatti.
Exhaust System made with a Titanium 3D Printing
Process
A special feature is the two exhaust hoods. Titanium 3D printing is used to create extremely thin double-walled structures, some as thin as 0.4mm, pushing the limits of technology. The lattice structure provides stability to the components and also provides space for air ducts. The double-wall construction insulates the titanium bezel, while airflow reduces its temperature. To protect the surrounding carbon components from overheating, the Chiron Super Sport adds air intakes to the underbody. Cool air circulates around the exhaust components and exits through the tailpipe trim. The exhaust gas stream can reach temperatures of up to 850 degrees and is surrounded by a layer of cold air. It prevents hot exhaust gases from hitting the rear of the car.
“Even at full power and top speed, exhaust gas does not influence any other components and is prevented from flowing back,” says Jens Wenge, Construction Engineer at Bugatti. Titanium itself reaches its melting point only at 1,668 degrees Celsius. Other advantages of titanium printing include precise edges and small gaps, leading to improved airflow properties and minimal rework. After the 3D-printing process is finished, a bezel is simply blasted and cleaned with compressed air. If desired, it can be painted black. In addition, a 3D-printed titanium component weighs only 930 grams, which is 570 grams or one-third lighter than a precision casting component.
W16-Engine with more Power and higher RPMs
To reach a top speed of 440 km/h, Bugatti upped the maximum output of the 8.0-liter W16 engine to 1,600 hp – an increase of 100 hp. For added flexibility, the engine offers an additional 300 rpm and a higher power platform at 7,100 rpm instead of 7,050 rpm. 1,600 Nm of torque is available between 2,250 and 7,000 rpm, up from 6,000 rpm previously. To improve performance, engineers redesigned many components. Pistons have been strengthened. Thanks to stiffer pressure control springs, the oil pump can now deliver more oil at higher pressures to engine components such as crankshaft, valves, chain drive, camshaft adjustment and piston cooling. At full load and rated speed, more than 140 liters of oil flow through the pump per minute.
Higher power and rpm result in increased vibration, which in turn puts more stress on the chain drive and valve train, including four camshafts and 64 valves. To improve durability at top speed, Bugatti has reduced the chain tensioner bearing bolts etc. This also requires modifications to the cylinder head. Improved valve springs with steel spring feet are now able to handle increased loads. To meet current legal acoustic requirements, a new multi-layer fibre-reinforced chain box is used to reduce noise emissions. A modified torsional damper on the crankshaft is mounted on the belt drive side for smoother engine operation. Bugatti has also retrofitted auxiliary unit drives, including generators, A/C compressors, water pumps and tandem pump to compensate for the higher speed.
More Efficient Turbochargers
In addition to the higher speed, the increased performance is also due to optimizations and a newly developed turbocharger. All four turbines now use a compressor wheel that has been enlarged from 74mm to 77mm for higher throughput. The diameter of the turbine wheel has been increased from 64.4mm to 67.2mm in order to be able to deliver more compressor power, which is required to increase boost pressure. At full load, 4.8 tons of air per hour flow through the four turbochargers. The optimization of the blade geometry increases the thermodynamic efficiency.
The throttle response is similar to that of the Chiron. “Despite the increase in performance, the weight of the engine is unaffected, and the response of the turbochargers remains at the same positive level provided by the 1,500 PS engine,” says Andreas Kurowski, Engine Development Engineer at Bugatti.
New Gear Ratio
To reach a top speed of 440 km/h, the 7-speed dual-clutch transmission uses new gear ratios. Compared to the Chiron, the seventh gear is 3.6% longer. Thanks to the improved performance, the 7-speed dual-clutch transmission shifts from sixth to seventh at full load and at full acceleration of 403 km/h. The Chiron Super Sport sprints from 0 to 200 km/h in 5.8 seconds and hits 300 km/h in 12.1 seconds. The difference is even greater when accelerating from 0 to 400 km/h, a speed that the Chiron Super Sport achieves in 28.6 seconds. This makes it 12% or 4 seconds faster than the Chiron. In order to prevent the driver and front passenger from noticing interruptions in traction when shifting gears, the boost pressure control for the individual gears has been further developed. Acceleration continues even at 6,000 rpm, giving the Chiron Super Sport a massive boost of up to 7,100 rpm.
Newly Developed and Refined Chassis
Bugatti redeveloped the chassis of the Chiron Super Sport with utter focus on high-speed performance and the car’s new aerodynamics. For this reason, engineers increased the rear axle spring rate by seven percent, compared to the Chiron, in order to further stabilize the Chiron Super Sport at speeds above 420 km/h. “The longtail design leads to a shift in axle load distribution, which we have taken into account when we tuned the chassis,” says Jachin Schwalbe, Head of Vehicle Development at Bugatti.
Combined with a longer rear and revised front, the Chiron Super Sport achieves improved air balance at high speeds. To do this, engineers retuned the electronically controlled chassis and adjusted the damping of the vehicle’s motion. Within six milliseconds, it adjusts the dampers and adapts to the vehicle’s movements in near real-time.
New Michelin Tires for Top Speed
Michelin’s newly developed Pilot Sport Cup 2 tyres, optimised for higher top speeds, provide higher stiffness and smoother running than the Chiron above 420km/h. A single tire was tested at speeds in excess of 500 km/h. This is achieved through a new technology with reinforcement layers that can withstand incredible forces – tested in a facility originally built for fighter jets. Front tires are 285/30 R20 ZR and rear tires are 355/25 R21 ZR. After production, each tire is X-rayed to detect even the smallest defects. The Michelin Pilot Sport Cup 2 tyres are designed for extreme longitudinal dynamics and thus support the philosophy of the Bugatti Chiron Super Sport.
Lightweight Rims with a New Design
To reduce unsprung mass, Bugatti developed new five-spoke aluminium rims, each 4kg lighter than the Chiron. They also increase the stiffness of the longitudinal dynamics and are therefore a perfect match for the Chiron Super Sport. As an option, Bugatti offers a set of magnesium alloy rims that are 16kg lighter than conventional Chiron rims, further reducing the unsprung mass on the axles. With the Chiron Super Sport, Bugatti has developed an extreme supercar. Numerous technical modifications and the pursuit of perfection make it the fastest production car, with its own personality, unique design and unparalleled luxury comfort. Bugatti manufactures the Chiron Super Sport at its headquarters in Molheim. The first vehicles will be delivered to new owners in early 2022 for a net price of 3.2 million euros.