BIG cars with small engines are becoming quite a common feature at the higher end of the new-car market.

Once-expensive twin-turbo technology is now extracting V8-like performance out of engines as small as Mercedes-Benz’s 2.1-litre four-cylinder engine, but without the big hit at the fuel pump.

Audi is the latest to join the twin-turbo diesel set, strapping a pair of exhaust-fed blowers to its 3.0-litre V6 engine to produce some numbers that truly raise an eyebrow.

It stars in the first diesel-engined Audi to wear a badge from the performance end of Audi’s model line-up – the SQ5 mid-size soft-roader – and extends to another couple of more mainstream models in the range including our test car here, the A7 Sportback.

The A7 Sportback is a four-door coupe version of the range-topping A8 limousine (though it shares much with the A6), but looks completely different to the more mainstream corporate shuttle thanks to those fastback looks.

Mercedes-Benz may have invented the four-door coupe with its CLS-Class, but latecomer Audi has taken the whole concept a step further, particularly with this engine.

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