Audi to start series production of A8 hybrid in 2012

Audi A8 hybrid. Click to enlarge.

Audi will start series production of the A8 hybrid in 2012. (Earlier post.) Its 2.0 TFSI gasoline engine and an electric motor develop peak output of 180 kW (245 hp) and 480 N·m (345 lb-ft) of torque. Average fuel consumption in the EU cycle is below 6.4 liters per 100 km (36.75 mpg US); CO₂ emissions are below 148 grams per km (238 g/mile). (All figures are provisional.)

The Audi A8 hybrid reaches 100 km/h (62.14 mph) in 7.7 seconds from a standing start and has a top speed of 235 km/h (146 mph). The sedan can travel at speeds of up to 100 km/h (62 mph) on electric power alone, and cover around three kilometers (1.86 miles) with zero local emissions at a constant speed of 60 km/h (37 mph).

The A8 hybrid is a parallel hybrid. The 2.0 TFSI, which has been modified in some areas, generates an output of 155 kW (211 hp) and 350 N·m (258 lb-ft) of torque, which is available between 1,500 and 4,200 rpm. The combustion engine works together with a disc-shaped electric motor which develops 40 kW (54 hp) and 210 N·m (155 lb-ft).

The permanent magnet synchronous 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. The fast-shifting hybrid transmission guides the torque to the front wheels; with its wide gear spread it contributes to the efficiency of the Audi A8 hybrid.

The driver has the choice of three modes: The EV characteristic map gives priority to the electric drive, while the D mode efficiently controls both the engine and the electric motor. The S mode and the tiptronic gate are designed for a sporty driving style.

The hybrid sedan has five operating states: with the TFSI engine alone, with electric drive only or in hybrid mode; recuperation and boosting are also possible. Two displays show the driver all operating modes in detail.

The lithium-ion battery, which weighs 36.7 kilograms (80.91 lb), is located in a crash-proof area in the trunk. It provides 1.3 kWh of nominal energy and up to 40 kW of power. Two different methods are used to air-cool the battery, depending on need: with air blown from the passenger compartment by a fan and via a separate cooling circuit coupled to the automatic air conditioning system. The battery is thus kept within the temperature window required for it to perform to its full potential over a wide range.

The electric motor and the compact power electronics which serve as a controller between the electric motor and the battery are water-cooled.

The Audi A8 hybrid will be one of the lightest sedans in its category. Its ASF (Audi Space Frame) body is made entirely of aluminum, while the B-pillars are of hot-shaped, ultra-high-strength steel. Weighing 231 kilograms (509 lb), it is roughly 40% lighter than a comparable steel construction.

Source: Green Car Congress