What is it?
The new range topping diesel version of Audi’s stylish A7 ‘coupe saloon’, now fitted with a twin-turbocharged 3-litre V6 engine that produces the dizzying combination of 308 bhp and 479 lb ft of torque – while still managing to return an official 44.1 mpg on the official test.
Barring the S7, which is powered by a twin-turbo petrol V8, the BiTDI is the quickest car in the A7 range. The same engine is also offered in the A6 and A6 Allroad.
Prices start at £52,330 for the SE version and £54,120 for the range-topping S-Line, as tested here.
However skeptical you might be about the idea of diesel performance cars, there’s no arguing that the twin-turbo engine is a seriously impressive bit of engineering, with a specific output of over 100bhp/ litre to accompany its prodigious torque peak.
The smaller of the two turbochargers spins up at lower engine speeds – being lighter, it has less inertia to overcome – with the larger rotor progressively taking over as the rev counter passes beyond 2500rpm. By the 4500rpm rpm where peak power arrives the bigger turbo is effectively working by itself. Audi claims a 5.3-sec 0-62mph time and a top speed that’s predictably curtailed by only a 155mph limiter.
The transmission is an eight-speed torque converter autobox – the engine’s torque curve being too much for the twin-clutch unit that Audi fits to the standard TDI and TFSI versions.
What's it like to drive?
Comically fast. It would take a long time for the novelty of the Audi’s thundering performance to wear off – in terms of real world pace, this is one of the very quickest cars on the road thanks to its combination of low-down torque and top-end power.
The autobox is willing to shuffle its ratios at close notice, and although there’s a slight hesitation between requesting full ahead and feeling the urge arrive, once acceleration starts it feels pretty much relentless. As previously confirmed on the Autobahn, this engine feels capable of running well past its 155mph limiter.
It sounds great, too – with a burbling big-cube soundtrack overlaid by a solid induction whoosh. If anything, the noise is closer to what you’d expect from a classic American muscle car than something that fills up at the black pump. And this isn’t one of the increasingly popular artificial electronic soundtracks, either – it’s just as good from outside the car.
The rest of the A7 remains as before, with lots of grip but over-light controls that rob it of ultimate driving appeal. The handling balance is impressively neutral for something this size – with the optional sports differential fitted to our test car helping to rechannel torque across via the Quattro four-wheel drive system to keep the car tight on a chosen line.
How does it compare?
The A7’s biggest rival is the BMW 640D Gran Coupe – a similarly stylish ‘coupe saloon’ that’s also powered by a twin-turbocharged 3-litre six. Power, torque and performance figures are effectively identical, but the Audi is nearly ten grand less.
Anything else I should know?
We managed 34.5mpg for 500 miles of rapid use.