Audi is set to take the fight to the recently unveiled BMW M6 GranCoupé with a new 552bhp twin-turbocharged 4.0-litre V8-powered RS7 Sportback.

Pictured here officially for the first time following its unveiling at the Detroit motor show today, the rapid liftback extends Audi’s RS line-up to six models.

Power for the RS7 Sportback comes from the same 4.0-litre V8 petrol engine used by the recently unveiled third-generation RS6 Avant. It produces 552bhp at 5700rpm and 76.45kgm of torque between 1750rpm and 5500rpm - some 138bhp and 20.46kgm more than the less highly tuned version of the same V8 in the S7 Sportback.

The new M6 GranCoupé’s twin-turbo 4.4-litre V8 produces the same 552bhp. However, it offers 7.18kgm less.

Because Audi’s seven-speed dual-clutch gearbox is unable to handle the heady torque loading of the engine, the RS7 Sportback receives a standard eight-speed automatic ’box. It operates in combination with the latest evolution of the Audi’s Quattro four-wheel drive system, offering the choice between D (drive), S (sport) and M (manual) modes. 

Audi is yet to confirm a kerb weight for its latest RS model but claims it delivers 0-100kph in 3.9sec and a top speed limited to 250kph. Buyers can raise the top speed to 280kph with an optional Dynamic package and to 305kph with a Dynamic Plus package.

Underpinning the RS7 Sportback is a heavily reworked version of the standard A7 Sportback’s chassis that features widened tracks and air suspension. Audi will also offer its new performance model with an optional steel-sprung suspension in combination with Dynamic Ride Control as part of a package known as Sport Suspension Plus — a move that is reflected on the new RS6 Avant.