The Audi S7 Sportback uses the same engine as the S6 and S6 Avant, the new 4.0 TFSI with 309 kW (420 hp) and 550 Nm (405.66 lb-ft) of torque. The twin-turbo V8 accelerates the five-door coupe from 0 to 100 km/h (62.14 mph) in 4.9 seconds, and top speed is limited to 250 km/h (155.34 mph). The cultivated eight-cylinder, which uses Audi's "cylinder on demand" technology under part load, consumes on average just 9.7 liters of fuel per 100 km (24.25 US mpg). Much of this groundbreaking efficiency can be attributed to the lightweight body. A hybrid aluminum construction, it weighs roughly 15 percent less than a comparable all-steel body. Lightweight components include the long rear hatch that opens and closes electrically as standard. Beneath it is a luggage compartment with a volume of 535 liters (18.89 cu ft), which increases to 1,390 liters (49.09 cu ft) with the rear seat backs folded down. Drivetrain and chassis Power transmission in the Audi S7 Sportback is provided by the dynamic seven-speed S tronic and the quattro permanent all-wheel drive system with a self-locking center differential and torque vectoring. The optional sport differential from Audi distributes the power in variable proportions between the rear wheels. The Audi S7 Sportback comes standard with the adaptive air suspension sport and the Audi drive select dynamics system. Mounted behind the 19-inch wheels are large, internally ventilated disc brakes front and rear. Their matt black calipers sport S7 logos up front. Carbon fiber-ceramic discs are available as an option.