2010 Audi S5 Sportback [Live image update]

Audi's sportiest Sportback, the S5 Sportback, was officially unveiled this week at the Frankfurt Motor Show. Based on the A5 Sportback revealed last month, the S model improves the all-around performance of the four-door coupe, thanks in large part to the addition of a supercharged V6.

The S5 Sportback features the same 3.0L turbocharged V6 found under the hood of the S4, tuned to produce 333 horsepower and 324 lb-ft of torque. Power is routed to all four wheels via Audi's seven-speed S tronic dual-clutch gearbox, netting 0-60 runs of just 5.4 seconds. Despite its high level of performance, the S5 Sportback still manages 24 mpg.

Buyers wanting to up the S5 Sportback's performance even further can order a torque-biasing rear differential.

U.S. sales of the S5 Sportback are unlikely - at best - but the Mercedes CLS competitor will hit the European market next spring.