The Audi A8 hybrid has been given the green light for series production beginning in 2012. Employing a four-cylinder gasoline engine for the first time in a premium Audi model, it will offer 245hp and 350 lb-ft, despite delivering sub-148g/km CO2 output and all-electric emissions-free running at speeds of up to 62mph.
The Audi flagship model is designed as a high-efficiency parallel hybrid. Its 2.0-liter TFSI engine, which has been modified in some areas, generates 211hp and makes a 260 lb-ft peak available between 1500 and 4200rpm. The combustion engine works together with a disc-shaped electric motor, which generates 54hp and 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 transmission. A multi-plate clutch that operates in an oil bath connects or disconnects the electric motor and the TFSI engine. The smooth and fast-shifting hybrid transmission guides the torque to the front wheels, and its wide gear spread contributes to the efficiency of the Audi A8 hybrid.
The short-term system output of 245hp and 350 lb-ft serve to provide impressively response. According to the provisional figures generated by early-stage tests, the Audi A8 hybrid will be capable of reaching 62mph from rest in 7.7 seconds and continuing to a top speed of 146mph, while returning in excess of 37mpg US in the EU combined cycle test, along with CO2 emissions of less than 148 g/km.
The Audi A8 hybrid can drive at up to 62mph purely on electric power and has a range of up to 1.86 miles at a constant 37mph. This gives the driver the choice of three modes: The ‘EV’ setting gives priority to the electric drive, while the ‘D’ option controls both the engine and the electric motor. The ‘S’ mode and the tiptronic gate place the emphasis on optimal acceleration.
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 81 lb, is located in a crash-proof area in the trunk. It provides 1.3 kWh of nominal energy and up to 40kW of power. Two different methods are used to air-cool the battery, depending on need: air is either blown from the passenger compartment by a fan, or 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.
In visual terms, the Audi A8 hybrid is distinguishable by subtle details such as its 18-inch or optional 19-inch ten-spoke wheels which resemble turbine blades, hybrid badges and an exclusive Arctic Silver paint finish. The metallic paint finish is a standard feature, as are three-zone automatic air conditioning, LED headlights and a Bose sound system.
Thanks to the brand’s ultra-lightweight construction expertise, the Audi A8 hybrid will be one of the lightest sedans in its category. Its Audi Space Frame body is made almost entirely of aluminum, with ultra-high-strength steel used only for the B-pillars to optimize rigidity. Weighing just 510 lb, it is roughly 40 per cent lighter than a comparable steel construction.