22/3/11

Overview: Lamborghini Aventador LP700-4

A carbon-fibre monocoque, pushrod suspension and a novel gearbox are the headline features of Lamborghini’s new flagship. A seven hundred horsepower V12, four-wheel drive and a price of roughly a quarter of a million pounds round the package off nicely. Styling, which is merely evolutionary by Lamborghini’s standards, is by Centro Stile Lamborghini; a transparent engine cover is available is you feel the Aventador is not conspicuous enough as it is.

The new car’s name — like that of many previous Lamborghinis — is that of a fighting bull. Specifically, Aventador was a bull that did battle in October 1993 at the Zaragoza Arena, earning the Trofeo de la Peña La Madroñera for its outstanding courage.

Lamborghini’s Aventador LP700-4 will be built at a new production facility in Sant’Agata Bolognese. It is very much a new car, replacing the Murciélago as the Company’s ultimate supercar. It is built along similar lines to the McLaren MP4-12C, with a carbon-fibre monocoque for the passenger compartment and aluminium structures to the front and rear. But the Lamborghini ups the ante on the British car rather substantially, with an extra four cylinders, three litres and 100PS. Its suspension struts are mounted horizontally and operated by pushrods in the style of a Formula 1 car, and the carbon-fibre centre section — unlike the McLaren’s — includes the roof as well as the tub.

The load-bearing structure of the vehicle is engineered as a single shell that functions physically as one component. The term ‘single shell’ applies only in the descriptive sense: the new Lamborghini monocoque is made from a number of individual parts with specific functions and technologies, such as stiffening elements made using braiding technology. After the curing process, though, the structure functions as a single component, including the base section — known as the tub — and the complete roof.

The entire monocoque weighs 147.5kg and was designed and built at Sant’Agata. All stages of testing and validation are also carried out in-house.

The monocoque is connected front and rear with rigid aluminum sub-frames, on which the suspension, engine and transmission are mounted.. The monocoque, together with the front and rear aluminium frames, has a torsional stiffness of 35,000 Nm per degree and weighs 229.5kg.

Depending on the form and function of an individual element of the carbon-fibre structure, one of three main CFRP manufacturing techniques was chosen. The techniques differ not only in their production processes, but also in the type of carbon fibre and its weave and, most importantly, in the chemical composition of the synthetic resin used.

Resin Transfer Moulding (RTM): In this process the carbon fibre mats are preformed and impregnated with an exact amount of resin. They are then cured under heat while the part is in the mould. Lamborghini has developed its own version of this process, known as ‘RTM-Lambo’: here, the final mould is no longer a heavy, complex piece of metal tooling, but is itself made from lightweight carbon-fibre parts. This makes the manufacturing process faster, more flexible and more efficient. An additional benefit of the RTM-Lambo process is the low injection pressure, cutting equipment costs.

Prepreg: The carbon fibre mats used in this method are pre-injected by the supplier with a thermosetting liquid resin and must be stored at low temperature. The mats are laminated in moulds and cured under heat and pressure in an autoclave. Prepreg components are complex to make, but have an extremely high-quality surface finish (known as Class-A surface quality) and are the preferred option for use in visible locations.

Braiding: The manufacturing method is RTM, but the weave of the carbon fibre is different. Weave technology is derived from the textile industry and used to make tubular components for special applications such as structural roof pillars and rocker panels. The woven components are made by diagonally interweaving the fibre in several layers.

Epoxy foam components are also used within the monocoque. They are placed in strategic points to increase the stiffness of the monocoque by working as spacers between the composite layers while also dampening noise and vibration. In addition, aluminum inserts are laminated into the front and rear surfaces to facilitate connection with the aluminum front and rear sub-frame elements.

Engine

The longitudinally-mounted 60-degree V12 is entirely new. Displacing 6496cc, it offers 107PS/l without forced induction. It is quite compact for a V12, and at 235kg dry it’s also fairly light. Headline outputs are 700PS at 8250rpm and 690Nm at a predictably hectic 5500rpm; Lamborghini boasts of a ‘well-rounded’ torque curve, however. There is an oil cooler to complement the coolant radiators, and cooling air intakes are electronically ‘managed’, opening and closing according to demand.

The specification for the new engine, known internally as the L539, was written quickly. Apart from having to deliver more power and torque than its predecessor, but it should also be smaller and lighter and enable a lower centre of gravity. Fuel consumption and emissions should also be reduced significantly.

The new power-unit measures 665mm in height, including the intake system. Its width, including the exhaust manifold, is 848mm, while its length is 784mm.

The crankcase is cast from aluminum alloyed with silicon. It has an open-deck construction with steel cylinder liners. Cylinder spacing is 103.5mm. The oversquare layout is traditional for high-revving engines, reducing internal friction and mean piston speeds. The forged and nitride-hardened crankshaft weighs 24.6kg.

The four-valve cylinder heads are also sand-cast aluminum alloy, each weighing 21kg. The twelve pistons and con-rods are, respectively, in forged alloy and steel. The maximum crankshaft speed of 8250rpm represents 21m/s at the piston, which is considerably less than for the Murciélago’s power unit. At 11.8:1, the compression ratio is very high.

Thermal management of modern car engines has become a science of its own. Lubicant and coolant must reach operating temperature quickly, allowing emissions and fuel-consumption to reach acceptable levels as soon as possible, but thereafter temperatures must be kept as stable as possible. With a high-performance power-unit like the Aventador’s, there is also the expectation of sustined high loads to deal with.

The new Lamborghini has two switchable water circuits in the engine: an ‘internal’ closed circuit for warm-up, with a limited coolant volume, and a normal circuit for general running. There are two coolant radiators.

Engine health, even under extreme racetrack conditions with high lateral acceleration, is provided for using dry sump lubrication. A total of eight scavenger pumps suck oil out of the lower bedplate fastened to the crankcase. A high-pressure oil pump maintains lubrication, while an oil/coolant heat-exchanger and an oil/air radiator keep temperatures under control. A further benefit of this form of dry sump lubrication is the very low mounting position of the engine within the car: the new engine is mounted 60mm lower than the V12 in the Murciélago, with the associated benefits in CoG and lateral dynamics.

From above, the V12 is dominated by its intake system. This incorporates four individual throttle valves, a distant echo of the four triple-choke Weber carburettors used on the Miura’s four-litre V12. Inside the black housing, the intake path length is adjusted using two flaps, several channels and one bypass. The payback is what Lamborghini describes as a ‘well-rounded’ torque curve.

The hydro-formed and thermally insulated three-into-one exhaust system incorporates four pre-catalytic converters close to the engine and two main catalytic converters shortly before the silencer. The casing incorporates two separate silencers — one low-volume, one high-volume. Regulated by valves controlled via the engine management, they control the exhaust note for the benefit of those who are deeply impressed by such things.

The engine’selectronic engine management was developed in its entirety by Lamborghini. The system consists of the main ECU, secondary ‘smart actuators’ and two additional black boxes that function as ‘smart sensors’. Because speed is everything for an engine like this, some ECU control and connection functions are handled by the smart actuators, making the ECU faster. The two smart sensors are constantly monitoring combustion in real time in each cylinder. The spark plugs function as sensors; the two auxiliary control units monitor the power signal after every ignition and can immediately identify irregularities in the combustion process through ionization phenomena.

Transmission

The Aventador’s transmission is quite novel, using multiple shafts to achieve very fast automated gearchanges without the bulk of a dual-clutch setup. We describe the independent shift rail (ISR) gearbox in detail elsewhere.

The Aventador LP 700-4 features permanent all-wheel drive — hence the ‘4’ in the model designation. An electronically controlled Haldex coupling distributes drive torque between front and rear, while a self-locking rear differential and electronically controlled front differential limit wheelspin. All four wheels are located by aluminum double wishbones suspension; a carbon-fibre ceramic brake system is used.

Inevitably, the car’s aerodynamics have come in for some attention. The underbody is flat, while the flow of cooling air into the engine compartment is controlled by electronically-operated vents. The large air intakes behind the passenger doors are permanently open, but when cooling requirements are particularly high, additional air channels open up on the rear wheel arches. The engine air intake is located on the roof pillar, and hot air exits through openings at the rear.

The rear spoiler is also controlled electronically. At rest, it lies flush with the rear of the vehicle; when deployed, it has two positions: at an angle of four degrees, or at 11 degrees. The former is designed for directional stability at very high speeds; the latter delivers downforce at mid-range speeds.

Bi-xenon headlamps are used. They are clustered with the LED units for daytime running lights and indicators.

Inside

The instrument display represents a fine example of technology without common sense. The display itself uses a TFT panel, which obviously has the potential to give the driver a huge amount of flexibility as to what he sees and how it is displayed. Unfortunately, this is not realised: in fact, the driver cannot even display the road speed and the engine speed at the same time, but must toggle between them. This is beyond mere eccentricity: it is possibly the daftest instrumentation feature we have encounted in a long while.

A second, 17cm TFT screen in the centre console belongs to the integrated multimedia system. Beneath it is an array of toggle switches for functions such as the electric windows or the front axle lifting system; beneath these are the controls for the air conditioning.

The most important switch — the start button — is hidden beneath a red switch cover on the console.

Running-gear

The Aventador driver can choose between five operating modes, affecting the engine, transmission, differential, stability control and servotronic steering. Three of the modes are manual, using the car’s gear-change paddles: Strada, Sport and Corsa. Strada means highway, Corsa means circuit or race. The two automatic modes are Strada-auto and Sport-auto. The Strada mode offers more comfort-orientated shifting. The Sport mode has a more ‘dynamic’ set-up in terms of shifting points and times, while the Corsa mode delivers the maximum shift strategy for race track driving. This mode also includes Launch Control, the automatic function for maximum acceleration from a standing start.

Various ECUs, networked, look after the drivetrain of this four-wheel drive car. An electronically-controlled coupling device distributes torque between the front and rear wheels, with the front getting between zero and 60 per cent.

Note the unusual mounting position for the radio: next to the driver’s right knee.

One of the Aventador’s more noteworthy features — perhaps behind it construction — is its pushrod spring and damper system. Aluminium double wishbone suspension at both ends locates the wheels, while the spring-damper units lie horizontally across the car, connected inboard to the bodyshell structure: under the windscreen in the front, close to the engine in the rear. This allows more flexibility to the stylist and aerodynamicist, while providing greater solidity for the mounting of the suspension units. A slight increase in total friction is the tradeoff.

This design offers various benefits. The combination of double wishbone and pushrod arrangement separates wheel location from damping. The solid connection to the monocoque improves the precision of the car’s responses to small inputs. As a result, spring stiffness can be notched back a little, improving comfort. On the front axle, the dampers are equipped with a hydraulic lifting system, which enables the front end of the car to be lifted by 40mm at the touch of a button, improving its ability to negotiate minor obstacles. We’re not dounting that the system works, but we’d not like to have to test it in anger...

The entire suspension system, including upper and lower control arms, wheel mounts and relay levers are made from forged aluminium alloy. The large-diameter brake discs are made from lightweight and extremely hard-wearing carbon ceramic composite material. On the front axle, the ventilated discs measure 400mm, with braking force delivered via six-cylinder calipers. On the rear axle, 380mm discs are used in combination with four-cylinder calipers. The parking brake on the new Lamborghini is electrically operated, happily not by a third pedal.

The weighting of the Aventador’s hydraulic power steering is controlled by the car’s driving mode selector.

Standard driver-assistance systems include ABS, electronic brake distribution, anti-slip control, speed-dependent servo-tronic steering, tyre-pressure monitoring, hill start assist and ESP stability control.

The first customers are expected to take delivery of the new Lamborghini Aventador LP 700-4 in late summer 2011. The price in Britain will be around £202,000 plus taxes.

Footnote

In the halcyon 1960s, the thought of driving across Europe in a Miura must have brought tears to the eyes of anyone who loved cars and driving. Empty roads and blissful ignorance of environmental matters equalled heaven. You just needed to watch out for bulldozers. Forty-odd years later, the world has changed so profoundly that, interesting though these supercars are from a technical standpoint, it is hard sometimes even to understand their continued existence. A recent spin on some wonderful roads in the north of England — in a car much humbler than the Aventador — brought home very starkly just how joyless the free world can be, with frequent roadside signs warning sternly that speeding motorists risked being caught by helicopter. If our rational society manages to take the fun out of even a nippy turbodiesel hatchback, what chance do we get to appreciate and enjoy the engineering prowess of a Lamborghini, Porsche or Ferrari?

Lamborghini Aventador
LP700-4
Miura
P400 S
Cylinders 12V 12V
Block/head Al/Al Al/Al
Valves 4 2
VVT IE
Aspiration A A
Bore/stroke 95.0/76.4 82.0/62.0
Swept volume 6498cc 3929cc
Compression
ratio
11.8:1 10.7:1
PS/rpm 700/8250 370/7700
Nm/rpm 690/5500 388/5500
Maximum speed 215 171
0-100km/h 2.9
0-60mph 6.7
Urban MPG
(l/100km)
10.3
(27.3)
Combined MPG
(l/100km)
16.4
(17.2)
CO2 g/km 398
Emissions EU5
Transmission AM7 M5
Driven wheels All Rear
Fuel tank 90l
Dry mass † 1575 1298
PS/t 444 285
Nm/t 438 299
Length 4780 4360
Width 2030 1760
Height 1136 1060
Wheelbase 2700 2500
Track
— front
— rear

1720
1700

1400
1400
Brakes
— front
— rear

400x38v
380x38v

Tyres
— front
— rear

255/35ZR19
335/30ZR20

GR70VR15
GR70VR15
† DIN kerb mass not available.
Text and design copyright © Under the Skin 2010-2011. We recommend Firefox.