Audi has taken the diesel engine from the S5, S6 and S7 TDI and slotted it into its more practical S4 and S4 Avant, creating the S4 TDI in the process.
As with its two-door brother, the S4 TDI is powered by a 3.0-litre V6 TDI engine making use of an electrically-powered compressor. It pumps out 255kW and 700Nm, the latter on tap between 2500rpm and 3100rpm.
The engine is shared with the S6 and S7 TDI revealed two weeks ago, and shoots the S4 to 100km/h in just 4.8 seconds, or 4.9 seconds in the Avant. Top speed is limited to 250km/h, while claimed fuel consumption is 6.2L/100km on the combined cycle.
Thanks to its 48V electrical architecture, the car has a 'belt alternator starter' and can recuperate energy into its 0.5kWh battery during deceleration. The setup allows the car to coast between 55 and 160km/h to save fuel, and means the start/stop can operate at speeds up to 22km/h.
It can also offer a boost under heavy acceleration, essentially using the car's electrical system to eliminate lag by manually driving the turbo when the engine isn't spinning fast enough to create the boost required. Apparently, the electric compressor can spin at up to 70,000rpm and respond in less than 250 milliseconds.
As for the rest of the car? Well, it's an S4. That means you get a range of performance options, like adaptive dampers and a sportier differential on the rear axle, and wheels up to 20 inches in size.
The usual tech features in the cabin, which means the driver is faced with a 12.3-inch digital instrument binnacle, and there's an 8.3-inch MMI display sitting atop the dashboard. Tech like adaptive cruise control, autonomous emergency braking, rear cross-traffic alert and turn assist is available, too.
Other standard equipment will include LED headlights with scrolling indicators, and powered front seats trimmed in leather and Alcantara.
We've contacted Audi to see if the S4 TDI is bound for our shores, but the S5, S6 and S7 variants with the same engines have remained forbidden fruit for our market. We'd suggest the same story is likely here.
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