and its makers
Technology at the Limit
No other car with the four rings is closer to motorsport; none is sharper, none is more dynamic. The new R8 high-performance sports car probes the limits of technical feasibility. We take a look behind the curtains at the development of its engine, ASF and quattro drive.
Lightweight design meets power –
in the new Audi R8, each hp has to shift
just 2.55 kilograms. Power: 449 kW (610 hp).
Curb weight: 1,555 kilograms.
What are the engine requirements for high-performance sports car? Plenty of power, of course; not to mention sound, tenacious responsiveness and high-revving euphoria. The further developed 5.2 FSI in the new R8 has all of this. When Christian Brinkmann, Head of Thermodynamics and Application V Spark-Ignition Engines at Audi, talks about the naturally aspirated V10 his eyes light up. “Our development work was more than passion,” says the engineer from Neckarsulm. “It was a kind of positive insanity.”
The vital statistics already hint at its thrilling potential. The engine, with a displacement of 5,204 cm3, delivers fulsome 449 kW (610 hp) at 8,250 rpm in the new R8 V10 plus; its maximum torque of 560 Nm kicks in at 6,500 rpm. Despite its long-stroke layout (bore × stroke 84.5 × 92.8 mm), the ten-cylinder spins up to 8,700 rpm. Here at the limit, the pistons reach their maximum average speed of 26.9 meters per second, circa. 100 km/h. The specific output is 117.2 hp per liter of displacement and each hp has to move just 2.55 kilograms of curb weight (minus driver). The fastest production Audi of all time shoots from 0 to 100 km/k in 3.2 seconds and from 0 to 200 km/h in 9.9 seconds. The acceleration doesn’t end until it reaches 330 km/h.
The 5.2 FSI is a hi-tech unit; even its basic layout indicates its close links with motorsport. All four camshafts can be adjusted by up to 42 degrees of crankshaft angle. Dry-sump lubrication means the engine can be mounted low down in the car. Its pump module guarantees lubrication even at the maximum possible lateral acceleration of 1.5 g. The crankcase, which has a V angle of 90 degrees, is made from a high-strength, lightweight aluminum-silicone alloy. The cylinder barrels are honed from solid.
The crankshaft of the V10 is conceived as a common-pin shaft, whereby the conrods of the opposing pistons are attached to a shared crank pin, leading to alternating ignition intervals of 54 and 90 degrees. This rhythm and the ignition sequence of 1 – 6 – 5 – 10 – 2 – 7 – 3 – 8 – 4 – 9 play a major role in defining the unmistakable sound of the new R8. Under load, the mighty, free-breathing engine plays a symphony of rumbling basses and powerful trebles that soars with the revs to a magnificent fortissimo, rounded off by the slap of the gearshift under full load and the burble on lifting off the gas. The acoustics can be fine tuned via two flaps in the exhaust, which can be controlled by the driver, and a switchable intake for untreated air.
And what’s new about the V10? This is where Brinkmann really starts to rave: “We have made the engine even more responsive and designed it even more for power output. Above 6,000 revs, it’s far more dynamic than its predecessor. And even when it’s running above the rated output, it still has plenty of oomph. If you push the pedal to the floor when the car is idling at a standstill, it reaches full load in just 66 hundredths of a second – almost 20 percent faster than the previous engine.”
Behind the increased power are first and foremost some classic measures – the compression ratio was raised from 12.5:1 to 12.7:1, valve control times have been set for good cylinder fill at high revs. Sophisticated detail work went into opening up the breathing – the valve heads on the exhaust side have a flatter design, while the intake valves have narrower shafts. The straight intake ports were shortened by ten millimeters, the tumble flaps and baffles removed – the 5.2 FSI no longer needs them thanks to the new dual injection.
The combination of manifold (MPI) and direct (FSI) injection makes a major contribution to performance. Only the new manifold injection is active under low partial load. The high vacuum in the manifold enables very good fuel evaporation and very few particulates are generated during combustion. Under midrange load, the work is split evenly between manifold and direct injection, with the FSI system, which develops up to 200 bar of pressure, taking on around 85 percent under full load. The remaining proportion of MPI contributes to good cylinder fill.
Two control units operating in accordance with the master/slave principle share the computing work. Brinkmann’s co-worker Dr. André Grob, Head of Thermodynamics and Application V8/V10 Spark- Ignition Engines provided the data, which is based on more than 20,000 values. “Beyond dual injection, we are also running a special efficiency technology – cylinder on demand (COD) – which we had to intricately integrate into the different operating modes,” says Dr. Grob. “Under low to medium load and revs, we deactivate one of the cylinder banks by switching off ignition and injection. This applies to the D drive program and the upper four gears. After a certain period of time, we reactivate the bank to ensure its catalyst doesn’t cool down and deactivate the other bank instead. The driver doesn’t notice anything, because the sound of the engine barely changes on five cylinders. And we modulate the transitions by deactivating the cylinders one after the other.”
Our development work was more than passion.
It was a kind of positive insanity from sheer enthusiasm
for the new engine.
Head of Thermodynamics and Application V Spark-Ignition Engines
The COD technology, the start/stop system and a coasting function in the seven-speed S tronic make the new Audi R8 V10 plus amazingly efficient. In the NEDC, its consumption has dropped from 12.9 liters per 100 kilometers (299 grams CO2 per kilometer) to 12.3 liters (287 grams). At 13 percent, the reduction in the new R8 V10, which produces 397 kW (540 hp), is even more. Even more power and even more passion paired with greater efficiency – that lights up the eyes of more than just the engineers.
Die spezifische Leistung des Top-V10 ist überragend:
Seine 610 PS resultieren aus 5.204 cm3 Hubraum.
AUDI R8 THE ASF
The development engineer –
Jürgen Gerbrand is responsible for developing the bodyshell structure of the Audi R8.
The right material in the right amounts in the right place – talking to Jürgen Gerbrand brings to life Audi’s classic principle of lightweight design. The engineer from Neckarsulm, responsible for the development of innovative bodyshell projects, knows all there is to know about the multi-material space frame of the new R8, about the strengths of the different materials and about the best methods for joining them with one another.
Gerbrand tells us that the space frame of the high-performance sports car weighs just 200 kilograms, a further 15 percent less than the previous model, which was already extremely light. Behind this incredible figure is a concept used by Audi for the first time – the front and rear ends of the car are still made from aluminum. However, the rear bulkhead, center tunnel and the three-part B-pillars are now made from carbon-fiber reinforced polymer (CFRP). Together, these parts make up 13 percent of the multi-material space frame and form a backbone of outstanding strength and torsional stiffness.
“We use CFRP specifically in those places where it achieves better results than aluminum and we specify it completely differently,” explains the development engineer. In the rear bulkhead’s transverse beam, where the number one priority its maximum lateral stiffness, the layers of webbing are arranged largely in one direction. There are around 14 of them one on top of the other, forming a layer five millimeters thick and taking full advantage of the extreme tensile strength of the pure fibers in the longitudinal direction – which measures 4,800 megapascals. In the B-pillar reinforcement, on the other hand, which has to accommodate both longitudinal and transverse loads, the layers are arranged in all directions (quasi isotropic orientation). Gerbrand: “In each location they’re used, the CFRP parts perform a specific task for which they are suitably structured.”
When it comes to aluminum parts, where the classic semi-finished components are castings, profiles and panels, the Audi space frame principle has likewise been extensively developed. The A-pillar nodes, which connect important components of the front-end and occupant cell, is made from a new, highstrength cast alloy with a tensile strength of 230 MPa, which is 15 percent higher than before. Altogether, the cast nodes represent 20.8 percent of the ASF.
In terms of the extruded profile, which makes up 47.2 percent, development work focused on increased tensile strength – with the new top figure of 340 MPa – and on optimized topology. “Between the suspension strut mount and the chassis connection to the rear axle is a vertical profile around 60 centimeters in length,” says Jürgen Gerbrand. “Its wall thickness varies between two and seven millimeters, resulting in a weight saving of 1.3 kilograms across the rear end as a whole.” Oval aluminum profile sections form the upper spider of the structural braces that stiffen the rear end – they weigh just one kilogram.
Cast nodes made from the new highstrength alloy connect the axle radius arms directly and stiffly to the ASF. The floor of the luggage compartment is made from sheet aluminum and functions as a shear plane. “We have achieved a new kind of functional integration here,” sums up Gerbrand. “Alongside new materials and improved geometries, this is our thirdbiggest discipline in lightweight engineering.”
The CFRP parts in the ASF fulfill a very specific task wherever
they are used. We’ve designed them with enormous precision.
Development Bodyshell Structure Audi R8
Cast parts, profile, heat-treated aluminum alloy sheet and CFRP – how do all these different materials come together to create a stiff, safe and vibrationoptimized space frame? Gerbrand cites the most important technologies in bodyshell engineering, “The welded seams between the aluminum parts are a total of 89 meters long. To connect them with the CFRP components we use cold processes only. The multi-material space frame contains 270 semi-hollow punch rivets, 207 blind rivets, 241 metric and 270 self-tapping screws. We ensure the aluminum does not corrode in those areas in contact with the CFRP through cathodic dip coating, with its drying oven set at around 200 degrees Celsius, a technical adhesive and a special sealant.”
In the lightweight rating – the relationship between weight, size and stiffness – the new multimaterial space frame achieves a top figure in its segment. When it comes to torsional stiffness – a particularly important figures for a sports car – it has increased by 40 percent. Jürgen Gerbrand: “Only through the new multi-material concept were we able to achieve these improved characteristics while reducing weight. If we had designed the space frame using the same technology as the previous model, it would have been 32 kilograms heavier.”
Weighing exactly 200 kg –
the new Audi R8’s multi-material space frame enters a whole new dimension
of lightweight design.
THE QUATTRO DRIVE
The development engineer –
Sebastian Straßis Head of Development Vehicle Control All-Wheel Drive Control Systems/Electrified Drives.
Audi is quattro and quattro is Audi – and that goes for the new R8, too. Especially here in the high-performance sports car, the permanent all-wheel drive system delivers a major plus in stability, precision and traction. “In the quattro drive for the new R8, we have achieved the very best that is possible today,” explains Sebastian Straßer, Head of Development Vehicle Control All-Wheel Drive Control Systems / Electrified Drives.
A high-performance mechanism and software that
offers us plenty of control parameters –
it’s this that gives the new quattro drive its supreme performance.
Head of Development Chassis Control,
All-Wheel Drive Control Systems/Electrified Drives
The heart of the new quattro driveline is an electro-hydraulically regulated multi-plate coupling integrated into the front axle differential. Inside it is an electrically driven axial piston pump. When the situation demands, it applies a pressure of up to 40 bar to push together the plates, which are made from steel and coated with an organic material. The higher the oil pressure, the more power is sent (continuously variably) to the front axle. To assure pressure buildup in a matter of milliseconds, the pump runs constantly with a certain oil volume.
“Compared with the unregulated viscous coupling on the previous model, the regulated multiplate coupling performs far better in all criteria,” says Straßer. “Before, we were only able to transfer a maximum of 30 percent of the torque to the front. It also necessitated a certain difference in the axle speeds. We are now able to apply the ideal torque distribution at any time, fully variably and depending on the actual driving conditions, because the new coupling has no fixed base distribution. Our intelligent all-wheel drive software has been adapted specifically to the mid-engine concept. It is constantly calculating the ideal torque distribution at any given moment, depending on the driving situation, driver input and environmental conditions.”
Management of the quattro drive is integrated into the Audi drive select dynamic handling system, which offers the choice between comfort, auto, dynamic and individual modes. In the R8 V10 plus (optional in the V10), the performance mode also offers dry, wet and snow programs, which adapt the handling parameters specifically to road surface friction. Handling characteristics are rounded off by the additional software system for wheel-selective torque vectoring – if required, it applies a slight braking force to the inside wheels when cornering.
To ensure drivers always have the full performance of quattro technology at their disposal, the multi-plate coupling is incorporated into the engine’s cooling circuit. This ensures it always performs precisely and to its full extent, regardless of load and outside temperature – from Saudi Arabia to the North Cape. Conditions are continually monitored by a pressure and temperature sensor and the control parameters adapted accordingly. Although the multi-plate coupling operates with a minimum amount of slip, which is necessary for defined torque transmission, it is still more efficient than the viscous coupling used in the previous model.
On the rear axle of the new Audi R8 is a mechanical differential lock that further improves traction and handling. With its 25 percent locking ratio under pull and 45 percent under push, it is designed specifically for the actively regulated quattro drive. Sebastian Straßer: “A high-performance mechanism and software that offers us plenty of control setscrews – it’s this combination that gives the new quattro drive its supreme performance.”
R8 drivetrain –
the multi-plate coupling is integrated into the front-axle differential
at the front end of the drive shaft.