Audi E-Tron Spyder Highlights Diesel PHEV Tech

By John O'Dell October 13, 2011

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Germans are a practical people, so when automakers such as the Volkswagen Group’s Audi churn out an expensive new concept car, there’s usually a retail version lurking somewhere in the background.  That the company flew the only existing version of its latest advanced-drive concept – the hand-built, $2.75-million (give or take) Audi E-Tron Spyder plug-in hybrid -- from Germany to Los Angeles to let U.S. journalists sample it says even more about the likelihood of production intent. It may be a few years, but it’s a pretty safe bet that some sort of a production mid-engine Audi roadster will be spawned by the diesel-electric, aluminum-and-carbon-fiber E-Tron Spyder concept.

AutoObserver got a few precious minutes behind the wheel of the topless 2-seater on the winding asphalt roads in the Santa Monica Mountains above Malibu, CA., earlier this week. The media preview marked the first time, Spyder project manager Uwe Haller said, that the Audi plug-in hybrid (PHEV) concept has been driven on public streets since its debut a year ago at the 2010 Paris auto show. Its twin-turbo diesel-electric powertrain isn’t likely to be what propels a retail version – too expensive, Haller suggested – but a standard gasoline or diesel engine from the Audi engine lineup is probable. A production version of this car likely would be slotted somewhere between Audi’s TT and R8 sports cars.

The concept was built in just two months last year after Audi executives gave the go-ahead to the idea of a roofless PHEV roadster to flesh out the lineup of advanced-drive concepts that began at the 2009 Frankfurt Auto Show with the all-electric, 4-motor E-tron coupe and was followed early last year with a shorter, lighter, 2-motor version introduced at the 2010 Detroit auto show. Although slightly wider and longer than its coupe cousin, the E-Tron Spyder borrows its wedgy, sharp-edged exterior design from the Detroit show car and incorporates many of the Detroit car’s interior and instrumentation touches as well. That includes Audi’s console-mounted, knob-shaped scroll pad with an integrated touch-sensitive surface so the driver, or passenger, can use a finger to write information such as addresses for the navigation system. The idea is to eliminate the need to use a dash-displayed touchscreen keyboard that diverts the driver’s attention from the road.

Less Distraction
Audi Etron Spyder Int 1.jpgAt a time many makers of advanced-drive vehicles are larding the instrument panel with enough powertrain information and infotainment displays to make an airline pilot feel right at home, Audi is using a minimalist approach for its electric and hybrid concept vehicles, said E-Tron Spyder interior design chief Gallitz Dorfer. “The focus is on the driver and the road and we just want to give the driver enough to use the car, so there is less distraction and not an overwhelming amount of information.”

Thus there are almost no extraneous knobs, dials or switches. The climate system is controlled by touch-sensitive slides hidden behind the floating dashboard’s thin aluminum trim strip and ignition is via a flush, console-mounted button. The single, round combination speedometer and information-display screen is flanked by four relatively tiny backlit displays – two on each side of the recessed speedo – that relate information about the state of charge of the hybrid battery, the climate-control settings, diesel fuel level and status of lights, oil pressure and coolant temperature. The rest is a clean sweep of hand-stitched leather trimmed in polished aluminum. The speedometer screen also displays the regenerative braking system gauge – showing how much electrical power is being restored to the hybrid batteries when the car is coasting or being braked.

New-Generation Diesel Engine
The E-Tron Spyder’s motive power comes from a new 3.0-liter, twin-turbocharged Audi TDI V6 diesel mounted behind the cockpit and a pair of front-mounted electric motors that draw their power from a 9.1 kilowatt-hour lithium-ion battery. The battery pack and the electronic power control system are packaged to ride above the motors under the clamshell front hood. The diesel has yet to be used in a production vehicle, but should appear in the next year or so in larger Audi sedans, Haller said. It produces 300 horsepower and an impressive 479 lb.-ft. of torque.

In a production Audi diesel hybrid, the engine would drive the real wheels via an electronically shifted 7-speed dual-clutch transmission. But the concept was cobbled together in two months and the dual-clutch transmission couldn’t be adapted to work with the hybrid system in such a short period, so it was replaced with a continually variable transmission (CVT) and the engine was detuned so as not to overwhelm the CVT. The electric motors – one for each of the front wheels – combine to produce about 88 horsepower and 260 lb.-ft. of torque. They deliver all that via a single-speed transmission. The layout means the E-Tron Spyder works part of the time as an all-wheel drive vehicle with full torque-vectoring (power apportioned to individual wheels as needed), with a default torque split of 75 percent of the power to the rear and 25 percent to the front.

New-Age Materials
Audi Etron Spyder Detail1jpg.jpgLike its predecessors, the E-Tron Spyder features an aluminum spaceframe – hand-built for the concept – clad in carbon-fiber reinforced plastic body panels for strength and light weight. The concept’s design parameters call for a car that carries a fairly large diesel engine, two electric motors, a 220-pound battery and its accompanying electronic controls and still weighs in at only 3,196 pounds, about the same as a the Audi TT convertible. As built, however, the car tipped the scales at a slightly overweight 3,638 pounds, closer to an A6 sedan. Audi and fellow German automakers BMW AG and Daimler AG’s Mercedes-Benz all are heavily involved in development of carbon fiber for body and structural parts because of its strength and light weight, but the material is expensive and hard to work with in large batches, so for now typically is reserved for high-end exotics and luxury cars.

31 Miles of All-Electric Range
Audi designed the E-Tron Spyder’s complex driveline to enable the driver to select a blended hybrid or all-electric drive mode – although the all-electric mode defaults to blended operation when the batteries are too low or the car’s speed exceeds 37 miles per hour. In blended mode, the electric motors provide the powerful diesel with even more boost for passing and hill climbing. In blended or all-electric modes, the motors alone can move the car along at speeds of up to 37 mph for as far as 31 miles. The concept is still a work in progress, so the switching was done manually via a computer hidden in the glove compartment. In blended mode, per Audi’s calculations, the diesel-electric system should propel the car to 62 mph from a standing start in just 4.4 seconds. Top speed is electronically limited to 155 mph.

By combining the frugality of a diesel – albeit a high-performance one – and a pair of electric motors that use no liquid fuel at all, the E-Tron Spyder theoretically would deliver combined U.S. highway and city fuel economy of 106.9 miles per gallon-equivalent. The car carries only 3.5 gallons of diesel fuel, but that’s extended by the power in its battery pack. Audi said a filled and fully charged Spyder should deliver up to 600 miles of range. Charging is via a 240-volt, Level 2 charger and takes about three hours.

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Production Intent?
Because the concept car is one-of-a-kind and intended only to foreshadow production possibilities, not deliver them, Audi permitted the E-Tron Spyder to be driven only for a few miles and only at speeds of less than 40 mph. Haller rode in the thin, low-slung, deeply bolstered passenger seat, wincing and uttering soft warnings whenever he saw a rock in the road or spied the speedometer edging close to the 40-mph limit. A California Highway Patrol car preceded the car and another followed, protecting it from other traffic and ensuring that E-Tron Spyder’s speed limit was heeded.

Whether the CHP will ever be chasing a production E-Tron Spyder along those same roads remains to be seen, but fans of Audis and fuel-efficient sports cars can take heart from the direction the company is headed: at the recent 2011 Frankfurt auto show one of the stars of the Audi display was a near-production version of an A8 E-Tron based on the original all-electric E-Tron coupe. Audi plans to bring the A8 E-Tron – which features an electric motor on each wheel – to market around the end of next year.

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