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4T : Miscellaneous Features

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28 December 2012


A few weeks ago word leaked out of Ingolstadt that the R8 e-tron project had been put on hold, finding itself in sort of limbo. A lack of technological advancement in battery technology and some other matters caused Audi to re-examine the project of producing an electric R8 as its first e-tron model, though it appears that doesn’t mean that the project has entirely stopped. The project remains a grand technological learning platform for Audi and as such Ingolstadt recently released more information on the R8 e-tron. As you can see in the accompanying pictures, it exposes some updates including the facelift components that have been applied to the newest production R8 models.

When Audi introduced the first e-tron concept at the Frankfurt IAA in 2009, the company’s then-current development boss Michael Dick stated he fully intended to put the car into production by this year. During the span of time since then, that production came into focus as an R8 e-tron with the first iteration of that car turning up at the 24 Hours of Le Mans in 2010. We eventually drove that first R8 e-tron, and subsequent versions of the car often painted red or white have been seen very regularly since that time, including setting a speed record for electric cars at the vaunted Nurburgring.

Then, following a re-examination of the project by Wolfgang Duerheimer earlier this year, the project found itself in the aforementioned hold status. On hold the R8 e-tron may remain, though this latest information about the car suggests it also remains a technology showcase for Audi and its burgeoning e-tron activities. Here’s the rundown on the latest generation and the one that most likely resembles any R8 e-tron that could eventually get cleared for production.

Unlike the all-wheel drive R8 F12 prototype we reported on earlier, the more production-oriented R8 e-tron remains rear-wheel drive. Power comes from two permanent-magnet synchronous motors mounted at the rear axle and capable of delivering 376 hp (280 Kw) and 604 ft-lbs (820 Nm) of torque, which will propel the R8 e-tron from 0-62 mph (0-100 km/h) in just 4.2 seconds. And, since the two motors operate independently, the R8 e-tron also boasts torque vectoring power delivery to the rear wheels. Think of this as similar to the advantages of the Sport Differential found in many modern Audi quattro models, though theoretically the system in the R8 e-tron can brake one wheel while providing full torque to the other.

From a safety standpoint, the drive control concept utilized by the e-tron’s motors is set up for redundancy and meets the highest safety standards. It coordinates demands for propulsion and also manages energy recuperation, the newly developed electric single-wheel anti-slip regulation (eASR) that provides stability (ESP) under braking as well as torque vectoring under acceleration.

Another advantage of the R8 e-tron is its ultra lightweight construction that is significantly more extensive than even the vaunted R8 GT. The e-tron’s curb weight is 3,924 lbs (1,780 kg). The bodyshell itself weighs just 439 lbs (199 kg). That’s a savings of 50.7 lbs (23 kg) thanks to the car’s Multimaterial Space Frame, which makes use of carbon-fiber reinforced plastic (CFRP). While it may look the same as a series production R8, the e-tron’s Multimaterial Space Frame shares just nine parts with the production R8 – the doors, exterior mirror housings, outer sill pieces, windshield crossmember and the roof arch. All other components are newly designed. Body panels are almost entirely manufactured using CFRP, including location-specific properties such as a seven-layer CFRP hood and just two layers necessary in places such as the inner shells of the rear side panels. The net result is that an impressive 23% of the bodyshell of the R8 e-tron is made from lightweight CFRP.

Structural safety is also part of the car’s generous use of CFRP. At the rear, a load-bearing luggage compartment shell is made of a carbon fiber design with wave-shape crash structure that ensures the e-tron can absorb five times more energy than a car with aluminum construction.

Closer inspection of the R8 e-tron’s running gear will reveal even more breakthroughs in ultra lightweight design. Springs are made from fiberglass-reinforced polymer (GRP) for a 40% weight savings over steel, wheel hubs are made of forged titanium and the anti-roll bar boasts hybrid aluminum and carbon fiber (CFRP) construction for a 35% weight savings. Even the 19-inch lightweight wehels are shod in friction-optimized 225-35 series tires.

The mass of the R8 e-tron’s lithium-ion battery is not insignificant at 1,272 lbs (577 kg). However, Audi engineers have managed to integrate the 235 cm long and 135 cm wide T-shaped battery within the Multimaterial Space frame as a load-bearing element with its supporting structure designed as high-strength aluminum plates. Most of this is can be found beneath the passenger cabin, which helps keep the R8 e-tron’s center of gravity as low as possible. Even better, the design of the battery as a structural element offers maximum torsional rigidity.

The battery component of the system is liquid-cooled and comprised of 530 prismatic cells. It stores 48.6 kWh of energy. As calculated by the metrics under the New European Driving Cycle (NEDC), this battery provides enough power to propel the R8 e-tron a calculated 133.6 miles (215 km). Completely exhausted, the battery can be recharged in less than an hour using a high-performance DC charging station or in about 12 hours via a domestic outlet. Also, Audi has developed an iPhone app that allows the driver of the R8 e-tron to manage the charging process and other functions from a remote location. Say you’re grabbing lunch with a friend on a cold winter day. You can have an extra espresso while you wait for the charging cycle to complete and instruct the e-tron’s heat pump to warm up the car (or cool it on a hot day) precisely in time for your planned departure.

The battery also recharges while driving using energy recuperation during deceleration – functionality that the driver can adjust to three different levels as well as full-on freewheeling via paddles on the steering wheel. The R8’s two electric motors handle most of the deceleration. Hydraulic brakes are used at the front, though electro-mechanical brakes are used at the rear so they can be synchronized electronically with the electric motors and utilized during heavier braking above 0.3g. The motors themselves can recuperate up to 0.45g.

Visually, this latest R8 e-tron looks as expected. Primary design differences between this car and previous e-tron prototypes center around R8 facelift elements such as headlights, taillights, hexagonal grille and rearview mirrors. Other cues have held close to previous generations of R8 e-tron prototypes including the matte carbon fiber finish on elements like the front spoiler, exterior mirror housings, sideblades, trunklid panel, rear lid fairing and diffuser.

Stylistically, Audi has implemented several R8 e-tron specific elements. The paint hue – Crescendo Red Metallic is familiar for those who’ve been watching the e-tron’s progression. New to this facelift are other elements that include fine chrome horizontal struts on the grille.

As with all Audi production models, lighting effects are instrumental in the car’s exterior design as well. The updated LED headlamps feature a differentiated e-tron-specific look. Horizontal LED light strips mounted behind the side windows feature the e-tron logo and provide a subtle illumination effect when the car is locked or unlocked or when the battery is charging. Another illuminated e-tron logo can also be found on the battery cover at the rear.

The final body design boasts cd figure of just 0.27 aided by a long rear diffuser incorporated into the underbody. This is significantly lower than the production R8’s 0.35 cd, though designers were able to skip the necessary openings for intake air or oil cooling. The vents at the side blades are closed in the case of the e-tron.

Cooling air for the e-tron enters via the lower section of the single-frame grille and flows through a channel that directs cooling through all components that comprise the car’s thermal management system. This includes an innovative multi-source heat pump that very efficiently and precisely maintains the temperature of no less than the battery, motors, transmission and power electronics and can also use the gathered heat to provide highly efficient climate control for the cabin itself. The design is extremely forward thinking and is based on the functional principle of the classic refrigeration cycle, utilizing a number of new components that include the chiller, front condenser/ evaporator, an electrically regulated expansion valve and an additional damper register in the air-conditioning unit. An Audi-developed heat coordinator manages the interaction of each participating system and selects the best of 43 variants in order to suit the present heating situation.

Of course since this is an e-tron, there are no engine, transmission or exhaust. As a result, designers were able to incorporate a completely smooth underbody that contributes greatly to the e-tron’s aerodynamic slipperiness. A long and steeply angled diffuser at the rear helps harmonize airflow over the rear of the car while the stock R8’s spoiler is unnecessary since speed is electronically limited to 124 mph (200 km/h).

Inside the cabin this is more than just a facelifted R8. Special controls and display elements are unique to the e-tron, with instrument panel and center-mounted 7-inch MMI displays that are much more functional than the production R8 and more like those found in models such as A7 and A8 that are equipped with the latest versions of MMI. Perhaps then it’s not surprising that the MMI system is controlled via the touchwheel-fitted controls sourced from the brand new MQB A3 and mounted in an entirely new center console design that is larger in order to house the battery components.

Higher graphic utilization in the MMI system is key for many components like graphic representations of range and energy flow. This includes LED strip representation on coolant temperature and battery charge status. Graphics also play a part in the utilization of a 6.7-inch Active Matrix Organic Light Emitting Diode (AMOLED) optic rear-view mirror system. Just seven millimeters thick the AMOLED display offers ten times better contrast while being 30% more energy efficient than a standard LCD monitor. Its response time is also unaffected by drops in ambient temperature.

Of course technology isn’t the only element that delights on the inside of the R8 e-tron. This cabin boasts plenty of CFRP carbon fiber surfaces accented with a plethora of leather and Alcantara in order to communicate all of the luxury and more that one would expect in an Audi R8.

Back outside and at speed, the R8 e-tron boasts Audi’s new e-sound functionality. Since the silent-running of an electric automobile can be dangerous in situations such as encountering a blind pedestrian, Audi has developed a unique sound for the e-tron emitted from a speaker system mounted in the underbody that is audible outside the car at speeds under 37 mph (60 km/h).

As of now, this latest R8 e-tron remains a technology platform and exhibit for Audi only. It is possible that the R8 e-tron could see very limited series production, though its assured status seems to no longer be the case. Just what model will mark Audi’s first full e-tron production car remains to be seen, though this R8 e-tron prototype certainly suggests that any ‘ur e-tron’ will be one very impressive piece of kit.

Technical Data
Power:                                     2×140 kW, 2×188 hp
Maximum Torque:                  2×410 Nm, 2×302 ft-lbs
Battery Capacity/ Voltage:     48.6 kWh/ 389 v
0-100 km/h (62 mph):             4.2 s
Range in the NEDC:               ca. 215 km
Top Speed:                             124 mph/ 200 km/h (electronically limited)
Length/ width / height:            4,431/ 2,029/ 1,252 mm
Wheelbase:                              2,650 mm
Curb weight:                           1,780 kg
Weight Distribution:               42:58

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