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Audi's Prologue concept sports the company's hexagonal grille that it uses to differentiate cars from the eight-sided grilles on its SUVs.

Audi shows design, fuel-cell directions

At the 2014 Los Angeles Auto Show, Audi exhibited its thinking on the future with a pair of vehicles, one showing its direction for exterior design and the other highlighting the future of electric drivetrains.

The Prologue concept car is a full-size luxury coupe that foretells the company’s styling plans for new models above the current A8 sedan, presumably to be called A9.

The concept coupe itself is, at 5100 mm (200 in) in length, slightly shorter than the A8 sedan. But the car’s styling is meant to introduce themes that will apply to smaller cars too, and is not intended as a literal representation of one specific future model, according to the car’s Chief Designer, Andreas Mindt. “This is a hint for the future,” he explained.

For example, the Prologue wears a broad, six-sided grille, which is to be Audi’s new standard for cars, while SUVs will have octagonal grilles, he said.

The Prologue’s crisp lines are meant to keep Audi’s still-familiar styling moving in a contemporary direction, Mindt said. “Audi is a design brand,” Mindt noted, and as such must continuously evolve its styling theme.

The Prologue rolls on show-car-typical 22-inch wheels and features Audi’s new signature laser headlights. The lasers don’t fire directly down the road, because that would obviously be a uselessly narrow beam. Instead, the laser strikes a projection lens that lights the whole street. That beam is supplemented with five smaller lenses fed their light via fiber optics, letting the light adapt to the conditions.

In contrast to some all-aluminum Audis today, the Prologue mixes aluminum with high-strength steel in its construction, perhaps to reinforce strategic areas for crash safety.

At the rear, the LED taillights continue the form language of today’s production lights, but underscore the Prologue’s width. Fine lines in the light’s glass impart a 3D effect when illuminated that creates the illusion of the light moving toward the observer when the brake lights illuminate.

Audi aimed to introduce significant innovations in the Prologue’s cabin.  Upon entering, the car identifies occupants by their smartphones and adjusts the seating and climate settings accordingly.

The dashboard contains an expanse of three flat-panel touch-screen LED displays that stretch across its entire width. Two are them are in front of the driver, with the left one used to manage lighting and assistance systems, while the right one handles media duties.

The passenger uses the third display panel to individually control entertainment features. The passenger can also set navigation routes, and with the flick of a finger, send them to the driver’s display.

The Prologue has a fourth, high-resolution organic LED (OLED) display on the center console, which is used to manage climate control and to input handwriting gestures.

Underneath, the Prologue’s significant innovation is the use of four-wheel steering. While this technology has so far found little favor with customers, Audi is confident that its time is coming, according to Ulrich Hackenberg, Volkswagen Group Board Member for Technical Development. “Four-wheel steering will be a typical feature in premium cars like this,” he said.

In the Prologue, the rear wheels steer as much as five degrees opposite the fronts for easier parking maneuvers, while they steer in parallel with the fronts at higher speeds for stability’s sake.

The car features a 445-kW (597-hp) 4.0-L turbocharged V8 engine that produces 750 N·m (553 lb·ft) driving through an eight-speed Tiptronic automatic transmission to power all four wheels using Audi’s quattro technology.

A new wrinkle is the addition of a 48-volt belt-alternator-starter mild hybrid system. It can recover as much as 12 kW of energy under braking and seamlessly restarts the engine when it is off. The company says that the system will soon be introduced in a production Audi model.

Under the more conventional shell of a production A7, Audi also introduced an innovative fuel-cell drivetrain that incorporates a plug-in hybrid electric drivetrain using a lithium-ion battery pack.

Audi has developed fuel-cell technology because of the slow progress in battery development, Hackenberg reported.  Fuel cells look like a better solution today, but “the performance of battery cells is increasing,” he said. “We have to compare which technology is the winner. We can’t answer now.”

With currently available technology, the company decided a blend of fuel cells and batteries would be best. The A7 Sportback h-tron quattro concept car’s primary drivetrain is a fuel-cell stack powering front and rear electric drive motors that power all four wheels.

Total power is 170 kW, with a combined 540 N·m (398 lb·ft) of torque, which accelerate the 1950-kg (4300-lb) car to 100 km/h (62 mph) in 7.9 s, reaching a top speed of 180 km/h (112 mph). Maximum driving range with full hydrogen tanks is more than 500 km (310 mi), and refilling those tanks takes three minutes, both factors that give fuel-cell EVs advantages over battery EVs.

The fuel cell achieves efficiency of 60%, making it almost twice as efficient as an internal combustion engine. Audi rates the concept car’s ability to travel 100 km on a kilogram of hydrogen as the equivalent of 62 mpg.

Audi says the fuel cell is guaranteed to operate at temperatures as low as -28°C (-18°F). Its four carbon-fiber composite outer shell/aluminum inner hydrogen tanks lie beneath the floor of the trunk and together store about 5 kg (11 lb) of hydrogen at 700 bar (10.2 ksi).

With this electric drivetrain in place, failure to recapture energy under braking would be a waste, so the engineering team added an 8.8 kW·h lithium-ion battery pack borrowed from the A3 Sportback e-tron. It not only increases the car’s efficiency through the use of recaptured brake energy, it contributes as much as 50 km (31 mi) of reserve driving range in the event there is no hydrogen available.

The plug-in battery pack charges in about four hours using 230-volt service, according to the company.

Hackenberg pronounced the A7 Sportback h-tron quattro’s fuel-cell technology ready for production, saying that the sole obstacle to the sale of such cars is the construction of a hydrogen fuel infrastructure to support it. “The first market will be the one with the infrastructure,” he said. “Right now, that is California, with Germany not far behind.”

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