Those who assumed the 2010 Audi S4 would share its powertrain with the S5 were incorrect. Instead, look for an all-new forced-induction 3.0-liter V-6 that will generate something close to the 340 horsepower found in the outgoing S4's 4.2-liter V-8.
Why is the Audi S4 moving from a V-8 to a V-6, just as the BMW M3 moved from an inline-six to a V-8? In two words: Fuel economy. 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%.
A less powerful, 290-hp, 310 lb-ft version of the engine will be the base offering in the A6 Quattro, replacing the 3.2-liter 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. While Volkswagen has a “twincharger,” Audi has not yet offered such a system. At the very least, we expect the new V-6 to be supercharged, although what will allow the S4's version to generate 50 or so more horsepower is still a mystery.
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Don't look for a dramatically lower weight in this S4. 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-the new S4 apparently was not developed by Audi's high-performance division, Quattro GmbH, but the S4 will be distinguished by having distinct cladding from the A4. 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.
We expect to see Audi roll out its Magna-sourced “sport differential” (BMW uses ZF) in the S5 and Q5 as well, to combat understeer in its four-wheel-drive vehicles. This trick differential, like the one in the BMW X6, 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 (although even Audi people still call it DSG, as it was originally known, and as VW still calls it), 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. Add in the requisite safety and luxury features that every new model gets, and it's a wash. Expect Audi to claim a nominal weight reduction of only 20–100 pounds for the new model, putting it at about 3900 pounds.
Audi will debut the 2010 S4 this fall sometime after the 2008 Paris show in October-making the L.A. show in November a possibility. Expect the new S4 to compete with the BMW 335i for efficiency but the Audi probably won't have the edge in performance and will cost significantly more. Watch for more details on the new S4's engine in the coming days.
