On the evening leading up to the opening day of the Paris Motor Show, Audi took the wraps of the much-anticipated 2010 S4 and S4 Avant. A perennial favorite with Audi enthusiasts, the big question on their minds is what lay beneath the Ingolstadt mid-size marvel’s hood; another V8, a turbocharged V6 or none of the above?

The answer is something completely new – a 3.0-liter direct injected, supercharged V6. Breaking with more than two decades of turbocharging tradition and a recent trend toward normally-aspirated V8s in the S4 and RS 4, this new engine delivers improvements in performance, drivability and fuel economy. And though it actually puts out a touch less horsepower than the outgoing V8-powered S4 (333 vs 340), it makes up for this with more torque, a meatier powerband (325 lb-ft @ 2500-4500 rpm vs 302 lb-ft @ 3500 rpm) and 26% better fuel economy.

The S4’s performance is matched with sport-tuned suspension, upgraded brakes and availability of an all-new 7-speed S tronic dual-clutch transmission (a 6-speed manual is still standard). Also new is the S4’s Drive Select feature, which allows the driver to choose between three settings that alter the engine’s throttle response, the S tronic transmission’s shift points and the responsiveness of the speed-sensitive servotronic steering. For drivers wanting even more performance, an optional quattroSport rear differential adds an enhanced level of traction and control during hard driving.

The S4 makes its sporting intentions clear without straying from its A4 roots. A different nose and tail, more aggressive rocker panels, aluminum-look mirrors and a discreet rear deck treatment give the S4 a quietly purposeful look. Add distinctive 18 inch wheels and a quartet of business-like exhaust tips and few will mistake the S4 for its more pedestrian sibling. Inside, S4-specific touches like sport seats, a sport steering wheel and trim accents (aluminum, carbon, wood or stainless steel mesh) further reinforce the car’s sport-oriented character.

While both the S4 sedan and S4 Avant will be available in Europe, sadly, American wagon fans will be disappointed to learn that like the current RS 4, only the sedan is coming stateside. When the S4 arrives next fall as a 2010 model, expect pricing to be roughly in line with the outgoing model.

Also shown at the VW Group’s preview event were the A1 Sportback concept and the A4 TDI concept e, a pair of low emissions vehicles. The diminutive A1 looks like a slightly smaller, more aggressive A3 complete with four doors and a unique split rear hatch. Under the hood, the A1 is propelled by a hybrid powerplant that combines a turbocharged 1.4-liter 150-horsepower 4-cylinder engine with a 27-horsepower electric motor. Small in size, but big on performance, Audi claims a 0-60-kph (62 mph) time of just 7.9 seconds in a car that also delivers over 60 mpg and has range of up to 60 miles on electric power only. Also noteworthy is the commendably low CO2 emissions rating of just 148 grams/mile.

Not quite as attention grabbing as the A1, but no less significant is the A4 TDI concept e, which showcases the company’s latest clean-diesel technology packaged in Audi’s best-selling mid-size sedan. Powered by a 120-horsepower 4-cylinder direct-injected turbo diesel (TDI), this near production-ready vehicle achieves hybrid-like fuel economy of 59 mpg, while emitting only 168 grams/mile of CO2. Similar to a hybrid, the A4 TDI concept e also employs start-stop technology to save fuel, as well as a recuperation system that recovers power under braking and coasting, converts it to electricity, and then temporarily stores it in a battery to save load on the alternator. No word on if/when this vehicle will arrive in showrooms (probably Europe only), but it definitely appears to be on the way.