Audi will unveil a hybrid version of its flagship A8 at the 2011 Frankfurt Auto Show next month ahead of series production of the vehicle kicking off next year. Audi says a 2.0 TFSI gasoline engine generating 155 kW (211 hp) and 350 Nm (258.15 lb-ft) of torque and a disc-shaped, permanent magnet, synchronous electric motor developing 40 kW (54 hp) and 210 Nm (154.89 lb-ft) combine for a peak output of 180 kW (245 hp) and 480 Nm (345.03 lb-ft) of torque and give the A8 hybrid the power of a six-cylinder model with the fuel consumption of a four-cylinder vehicle.

The A8 hybrid boasts an average fuel consumption of below 6.4 liters per 100 km (36.75 US mpg) and can travel at speeds of up to 100 km/h (62 mph) or cover around three kilometers (1.86 miles) at a constant speed of 60 km/h (37.3 mph) on electric power alone. The vehicle can accelerate from zero to 100 km (62 mph) in 7.7 seconds on the way to a top speed of 235 km/h (146 mph).

In addition to being powered by either the TFSI engine or electric motor alone, the vehicle also offers three hybrid modes. The EV characteristic map gives priority to the electric motor, while the D mode controls both the engine and electric motor to maximize efficiency. Meanwhile, the S mode uses all available power and re-maps the transmission shift points for a sporty driving style.

The hybrid drive is designed for electric-powered driving up to 65 km/h (40.4 mph), after which the TFSI engine alone does all the propulsive work while the electric motor powers the vehicle's electronic systems and recharges the battery. When the driver lets up on the gas, the combustion engine is disconnected from the drivetrain, so the vehicle "sails" and the electric motor acts as a generator to recharge the battery.

The electric motor is mounted in the space usually occupied by the torque converter in front of the modified eight-speed tiptronic. A multi-plate clutch that operates in an oil bath connects or disconnects the electric motor and the TFSI engine, while Audi says a wide gear spread contributes to the vehicle's efficiency. The lithium-ion battery pack, which weighs 36.7 kg (80.9 lb), is protected by a high-strength housing and features a ventilation module to ensure it is always in the ideal temperature range. Despite the battery pack being housed in the trunk, the A8 hybrid provides 400 liters (14.13 cubic feet) of luggage space.

The Audio A8 hybrid will come with Bose sound system, LED headlights, three-zone climate control, metallic paint finish and ten spoke 18-inch alloy wheels as standard, with 19-inchers and an exclusive Arctic Silver paint finish available as options. Its frame is made entirely of aluminum, while the B-pillars are of hot-shaped, ultra-high-strength steel. Weighing in at 231 kg (509.27 lb), Audi claims it is roughly 40 percent lighter than comparable steel construction frames.

Audi will debut the A8 hybrid at the 2011 Frankfurt Auto Show, which runs from September 15 to 25, with the car set to enter production in 2012.

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