The Audi A8 hybrid is designed as a parallel hybrid – a straight-line concept with high efficiency. Its combustion engine and the electric motor are located one directly behind the other and are linked by a clutch to work together, when necessary. The interplay between the combustion engine and the electric motor briefly results in a peak system output of 180 kW (245 hp) and a maximum system torque of 480 Nm (354.03 lb ft).
The Audi A8 hybrid combines the performance of a six-cylinder with the fuel economy of a four-cylinder model. The sprint to 100 km/h (62.14 mph) takes 7.7 seconds, and top speed is 235 km/h (146.02 mph). In the standard cycle, the luxury sedan consumes just 6.3 liters of fuel per 100 km (37.34 US mpg) on average – a CO2 equivalent of 147 grams per km (236.57 g/mile) and easily the best in its class. For the A8 L hybrid, these figures (all figures provisional) are 7.9 seconds, 228 km/h (141.67 mph), 6.4 liters per 100 km (36.75 US mpg) and 149 grams of CO2 per km (239.79 g/mile). The 75 liter (19.81 US gallon) tank gives both versions a long range.
The 2.0 TFSI displaces 1,984 cc and produces 155 kW (211 hp). Its maximum torque of 350 Nm (258.15 lb-ft) is available between 1,500 and 4,200 rpm. The four-cylinder engine, which has been chosen as Engine of the Year five times in a row, combines gasoline direct injection with turbocharging – typical for the Audi philosophy of downsizing, which replaces displacement by forced induction.
The Audi valvelift system (AVS) further increases power, torque and efficiency by switching the stroke of the exhaust valves between two stages depending on the load and engine speed.
The 2.0 TFSI has been overhauled in some respects for use in the Audi A8 hybrid. The mechanical belt drive for the auxiliaries was eliminated; it was electrified for the hybrid. A secondary air system at the cylinder head makes sure that the exhaust gas treatment cuts in particularly fast after cold-starting.
Quiet on board: Active Noise Control
The Audi A8 hybrid comes standard with Active Noise Control (ANC). This innovative system eliminates intrusive engine noise by broadcasting a precise antiphase sound to the cabin through the sound system’s speakers. This principle is known as interference: If two waves of the same frequency are superimposed, their amplitudes cancel each other out provided that they are equal and 180 degrees out of phase from one another.
A highly modified eight-speed tiptronic transfers the power to the front wheels. Instead of a torque converter, it includes the disk-shaped electric motor, which is combined with a multi-plate clutch operating in an oil bath. The clutch connects and disconnects the electric motor and the TFSI very precisely and gently.
With its eight widely spaced gears, the comfortably and fast-shifting hybrid transmission contributes significantly to the efficiency of the Audi A8 hybrid. When the 2.0 TFSI is deactivated, an electric pump maintains the oil pressure in the hydraulic system to safeguard the convenient start-stop feature.
The power electronics, connected to the battery and the electric motor by high-voltage cabling, are located in the plenum chamber of the engine compartment. They serve as a controller between the battery, which outputs direct current, and the electric motor, which operates on alternating current. Innovative technologies keep the volume and weight of the component low, with cooling provided by a separate water-filled circuit. The power electronics include a DC/DC converter that connects the consumers in the 12 V electrical system to the high-voltage network.
Electric drive is a permanent magnet synchronous machine; it serves as an electric motor, as a starter and – during deceleration – as a generator. The electric motor, which delivers up to 40 kW (54 hp) of power and 210 Nm (154.89 lb ft) of torque, is integrated into the engine’s cooling system.
Energy is stored in a lithium-ion battery system weighing a mere 38 kg (83.78 lb). It is located in a crash-safe area of the trunk and protected by a separate housing. The battery consists of 72 cells; at 266 volts its normal energy is 1.3 kWh and its power 39 kW.
The lithium-ion battery is cooled by air in two ways. At low-temperature load, it draws temperature-controlled air from the vehicle interior by way of a fan. If its temperature exceeds a certain limit, a separate refrigerant circuit is activated. It is coupled to the main climate control system of the vehicle and uses a separate evaporator. This powerful active cooling makes Audi A8 hybrid superior to many other hybrid vehicles.
The equipment and data specified in this document refer to the model range offered in Germany. Subject to change without notice; errors and omissions excepted.