Like its predecessor the Bugatti Veyron, the new Bugatti Chiron is a true engineering marvel. It’s a 1,478 horsepower monster capable of doing 261 mph a despite considerable bulk of 4,400 pounds. Here’s some of the goodness that makes the Chiron one of the most technologically impressive cars the world has ever seen.
With a price tag that translates to $2.5 million at the current exchange rate, the Chiron is meant as a very expensive engineering exercise, a showcase of the Volkswagen Group’s engineering and design talent at the highest level.
Sure, it looks a lot like the Veyron, its electronically-limited top speed is about the same, and a lot of the powertrain and chassis components share similarities, but the Chiron is still an engineering nerd’s wet dream, even if it’s not as revolutionary as its brother. And at least until the Koenigsegg Regera comes out for real later this year, it can claim the title of the most powerful car in production.
Yet while it does all of this magic without the aid of electric power, like many modern hybrid hypercars, the Chiron is still all about moving the technological needle, Wolfgang Dürheimer, President of Bugatti Automobiles S.A.S., said at the debut:
It is part of human nature to cross boundaries and set new records – to run 100 m faster than ever before, to fly even further into space and to enter new realms. This striving is also our driving force at Bugatti.
That’s a fancy auto exec way of saying they’re trying to show off, and boy, have they built a car worth flaunting.
The old Veyron was more than just an obscenely high-priced seven figure toy for athletes, hip-hop stars and oligarchs, although it was certainly also used that way. It was built to take the title of the world’s fastest car, and indeed held some of those records for a while (or at least laid claim to them.)
Can the Chiron one-up its older brother? It has one hell of a legacy to live up to. Here’s how it will try.
The engine in the Chiron looks a lot like the old one found in the Veyron. Again it displaces eight liters, looks like two narrow V8s bolted together to form a W16, and has four turbochargers.
But to get the Chiron to nearly 1,500 horsepower—25 percent more power than the Veyron—engineers had to figure out how to cram more air and fuel into those cylinders. They achieved this via new turbochargers and a new Charge Air Cooling (intercooling) system to squeeze in more air, and revised fuel injectors to keep up with all that airflow.
The new turbos are controlled by a two-stage system, replacing the parallel system in the Veyron. This likely means that now, instead of four cylinders each feeding exhaust to a single turbo turbine, a bank of eight cylinders feed two turbos in series.
To minimize turbo lag, at low engine speeds—below 3,800 in the case of the Chiron—intake air only gets compressed by the first turbo in series (likely one turbo on each bank). At RPMs above 3,800, intake air is compressed twice as it is sent through both turbos on each bank, allowing for more air to enter cylinders for better volumetric efficiency.
The increase in intake air pressure after going through a turbo is accompanied by a temperature increase, which makes intake gases not only less dense, but also causes possible issues with combustion stability. To fix this, Bugatti says they’ve made improvements to their charge air cooling system, though they don’t specify the changes.
To cope with all that air being shoved into the cylinders, the Chiron gets 32 Duplex fuel injectors to ensure a proper air/fuel ratio and to shoot fuel in a way that optimizes combustion efficiency.
The result: More than 60,000 liters (15,850 gallons) of air get forced through the engine every minute by the Chiron’s turbochargers and the torque curve is flat, with 1,180 lb-ft of torque made between 2,000 and 6,000 rpm.
In addition to the new turbos, charge air cooler and fuel injectors, the Chiron makes more power thanks to a new less-restrictive titanium exhaust system.
The exhaust system is insulated (possibly to warm up catalytic converters or to prevent radiation to the underhood and nearby sensitive components), and outfitted with four pre-converters and two main catalytic converters, which are much larger than those in the Veyron. Bugatti says they’re six times larger than catalytic converters found in medium-sized cars.
The surface area of the exhaust catalyst is 230,266 m², which Bugatti says is about the same size as 30 soccer fields.
Bugatti says it designed the seven-speed dual-clutch transmission to handle the Chiron’s 1,180 lb-ft of torque and that it’s got “the largest, highest-performance clutch fitted to a passenger car.”
We don’t know how different the new trans is from the Veyron’s seven-speed DCT, but the press release does seem to imply that the gearbox was developed specifically for the Chiron. What that means exactly, we don’t know.
Like on the Veyron, the Chiron’s transmission sends power to all four wheels.
The front and rear differentials get a locking function, which makes sense, because 1,180 lb-ft of torque trying to spin only two wheels would be a mess.
You can’t accelerate a lead-weight body to 60 MPH in less than 2.5 seconds, so the Chiron gets the latest in carbon-fiber goodness.
The Chiron is built on a fully carbon-fiber unibody, unlike the Veyron whose rear section was also steel. (Somehow, the Veyron is still over 100 pounds lighter). Bugatti says “If all the fibres used in the monocoque were laid out end to end, they would stretch nine times the distance between the earth and the moon,” and that the monocoque takes four whole weeks to make.
To cope with the ridiculous loads that torquey engine imparts on the body, you’d hope the Chiron’s tub were very stiff. On that front, Bugatti promises a torsional rigidity (resistance to twisting) of 50,000 Nm per degree of twist and and a flexural rigidity (resistance to bending) of about 0.25 mm of deflection per tonne, numbers that Bugatti says are similar to those of LMP1 race cars.
The Chiron gets five drive modes in what Bugatti refers to as an “adaptive chassis.” The drive modes include: lift, Auto, Autobahn, Handling and Top Speed, the first four of which are activated via a dial on the steering wheel, and the last of which is activated via a special key.
To engage these modes, Active Chassis varies ride height adjustment, shock damping, electric power steering feel, four-wheel drive system including the rear diff lock, the aerodynamic control system and the vehicle stability control.
The Lift mode raises the suspension for easy trailering. The auto mode engages above 50 km/h and actively adjusts shock damping and ride height for comfort and handling. Above 180 km/h, autobahn mode kicks on, and dampers are set for comfort and high-speed stability. In Handling Mode, dampers and steering are set for the twisties, and ride comfort is put on the back burner.
Then there’s Top Speed mode, which is activated via a separate key (called the Speed Key), and allows the vehicle to reach its top speed of 261 MPH.
Chassis and Tires
The Chiron’s brakes are 20 mm larger and 2 mm thicker than those on the Veyron, allowing for more heat dissipation. They’re also lighter, and squeezed by brand new brake calipers with titanium pistons. The front calipers get eight-pistons, while the rears make do with six. The pistons on each caliper are difference sizes, Bugatti says, in order to ensure even brake distribution on the brake pad.
Along with new brakes, the Chiron gets a new electric power steering system, revised axles front and rear, and new chassis bushings, all of which Bugatti says “[ensure] optimum reactions to driver input.”
Like those on the Veyron, the Chiron’s tires have been co-developed with Michelin. They’ve got to withstand 3,688 lb-ft of torque per wheel, and every gram of rubber is exposed to centrifugal force of 3,800 times the force of gravity.
The tires, 285 / 30 R20 at the front and 355 / 25 R21 in the back, are also simpler to instal than those on the Veyron and are less expensive overall. That’s a good thing, because a new set of tires on the Veyron were almost 40 grand.
Aerodynamics and Cooling System
Cooling System and Aerodynamics
Aerodynamics and engine cooling are intrinsically linked. Radiators need airflow to reject heat produced by the powertrain, but that airflow entering the radiators causes drag known as “cooling drag.”
When designing a car whose goal it is to reach a very high top speed, minimizing cooling drag while still keeping the engine cool can be very tricky. Bugatti says their 1,500 horsepower engine can generate more than 3,000 horsepower of heat rejection, much of which needs to be dissipated by heat exchangers.
To cope with that need, the Chiron’s got a water pump that pumps about 200 gallons per minute through one main radiator and two auxiliary radiators. There’s also a 12-liter low temperature cooling loop for the intercooler. Add the three engine oil coolers, the transmission oil cooler, the hydraulic oil cooler and the rear diff cooler, and the Chiron’s got a total of 10 radiators.
A typical high performance track-oriented car like the GT350R might have a four or five heat exchangers: one radiator for the engine, a transmission cooler, maybe an auxiliary oil cooler, perhaps a low temperature radiator for an intercooler and/or turbo, and maybe another auxiliary heat exchanger for the engine. Hybrids add more heat exchangers for batteries and other electronic components, but 10 radiators is unheard of. Well, except for on the Veyron.
Despite all those heat exchangers, the Chiron can stay cool even with its lower frontal area and small low coefficient largely because of its clever ducting that ducts air out and around the car after it’s gone through a heat exchanger, thus minimize cooling drag.
Bugatti identifies major aerodynamic enablers as: “air curtain, the aerodynamic front splitter, the front air intakes for the cooling of brakes, water and air [heat exchangers], the air intakes of the oil cooler and the engine air inlets on the sides as well as the continuous trailing edge on the rear of the vehicle.”
Aside from those passive aerodynamic features, the Chiron also gets hydraulically-controlled active aerodynamics, which includes a diffuser flap out front for decreased drag and better brake cooling and the active air brake in the back for stability and braking. That rear air brake spoiler in the back has four main positions, but adapts its angle and level automatically based on the driving condition. In addition, the variable ride height also decreases overall vehicle drag, meaning the Chiron’s drag aerodynamic properties are constantly changing.
So sure, some of the Chiron’s tech looks a lot like its predecessor’s, and it weighs a bit more. But you have to wonder if, without that speed limiter and with development time, the Chiron will take away all of the Veyron’s speed records.
Something tells me the answer is yes.
source: gizmodo.com by David Tracy