Audi S4 gets mild-hybrid V6 diesel

The Audi S4 sedan and Avant wagon will soon be offered with a powerful mild-hybrid turbocharged V6 diesel that promises to blend stonking performance with surprising efficiency, at least in Europe.

Borrowing its 3.0-litre V6 mild-hybrid turbo-diesel from the S6 and S7 TDI models available in Europe, the small Audi S4 TDI produces 255kW and 700Nm of torque.

Combined with the firm's quattro all-wheel drive, the Audi S4 sedan is capable of a 4.8-second dash to 100km/h and a top speed of 250km/h while being able to average a very respectable 6.2L/100km, says Audi.

Like its bigger brothers, the power and efficiency gains are thanks to Audi's 48-volt mild-hybrid technology that sees the 3.0-litre V6 diesel come equipped with both a large exhaust-driven turbocharger, a smaller electric compressor and a belt-driven alternator.

Clawing back energy under braking to charge a small 0.5kWh lithium-ion battery, the electric motor-powered compressor kicks in iduring the momentary pause before the big turbo spools up to eliminate turbo lag.

That belt-driven alternator boosts efficiency, meanwhile, by allowing the S4 to coast for up to 40 seconds saving fuel, while under acceleration it can recover as much as 8kW of power.

The powerful TDI mild-hybrid has also been announced for the sportier S5, but the electrified TDI engine has not yet been confirmed for Australia for either the coupe, sedan or wagon.