AUBURN HILLS, MI – The 2010 Audi S4’s powertrain will feature an all-new forced-induction 3.0L V-6 that will generate something close to the 340 horsepower found in the outgoing S4’s 4.2L V-8. Audi’s strategy is to deliver comparable or improved overall performance by toeing the line on weight and maintaining power output by using forced induction on a smaller displacement engine. Doing so will boost a manual transmission S4’s fuel economy on the European cycle to 23.3 mpg compared with only 19.4 mpg for the V-8 S5. That’s an efficiency gain of 20 percent, according to www.caranddriver.com.

A less powerful, 290-hp, 310 lb-ft version of the engine will be the base offering in the A6 Quattro, replacing the 3.2L V-6. Known as TFSI, which in the past has been Audi’s internal moniker for four-cylinder turbos, the new engine may be referred to as the 3.0T in the model name, possibly indicating a twin-charged system using both a supercharger and a turbocharger, the report said. While Volkswagen has a “twincharger,” Audi has not yet offered such a system.

Compared with the outgoing 2008 A4, the redesigned 2009 A4’s body is approximately 10 percent lighter. The A4 and S4 will use identical sheetmetal this time around. Not only does the sharing save money, but stresses the exclusivity of the RS 4 which will better stand out with its distinct sheetmetal—including bulging fenders—and a V-8.

Car and Driver expects to see Audi roll out its Magna-sourced “sport differential” in the S5 and Q5 to combat understeer in its four-wheel-drive vehicles. This trick differential adds about 40 pounds.

The S4 will be the first Audi vehicle in the U.S. with a longitudinal engine layout to offer a dual-clutch transmission. Now known as S tronic, this seven-speed sequential-manual will further improve performance and efficiency. The supercharger will make the V-6 weigh about the same as the V-8 overall.

Audi will debut the 2010 S4 this fall after the 2008 Paris show in October.