THERE'S SOMETHING UTTERLY improbable about the Audi RS7 Sportback. Look beyond its rakish, four-door-coupe lines and you find an immensely practical piece of kit that accommodates four decentsized people in considerable style and comfort. Raise the hatch that covers its sleek rear end and you discover a voluminous, 535-litre cargo bay in which you can stow a liberal selection of LV's finest and still find room for the supermarket run. Engage Comfort mode from the menu of options on the Drive Select System, and you can pootle around the city as meekly and innocuously as if auntie had offered you a ride in her Corolla.
But floor the accelerator and the Sportback morphs into a monster – which is exactly how I start thinking about the big red beast just minutes after picking up the keys on a stormy Friday morning in May. Of course I'm well aware that any Audi bearing the “RS” (rennsport) nomenclature is going to be extraordinarily quick, but even I'm flabbergasted at the way this behemoth goes ballistic when a gap in the outer lane opens up and I aim for it.
The engine, which until now has been quietly burbling on just four of its eight cylinders, emits a fearsome roar as the remaining quartet kicks in, the rev counter jerks sharply northwards and, with plumes of spray kicked up by the ultra-low-profile 275-section tyres, the car not so much accelerates as erupts into the faster stream of traffic. Weighing the better part of two tonnes, the RS7 is a hefty brute indeed, yet with more than 550bhp and a gargantuan 700Nm of twist from its twin-turbocharged 4-litre V8, its performance verges on the surreal. From a standstill, 100km/h appears in just 3.9 seconds and, with the Dynamic Package Plus optioned – the high-tech bundle also includes carbon-ceramic brakes, RS sports suspension with Dynamic Ride Control, and Dynamic Steering – top speed is more than 300km/h. (Regular RS7s, if such a word can be used to describe them, are limited to the more usual 250.) I'm sticking my neck out and claiming that numbers such as these, which would do several supercars proud and even encroach on hypercar territory, are hitherto unheard of for a four-door – or, more accurately, a five-door – saloon, though possibly a Panamera Turbo S could top them.
One of the best high-performance powerplants on the road, the RS7's wonderful engine is a further uprated development of the unit in the Bentley Continental GT V8 and the Audi S7 and S8, for which it produces 500bhp and 513bhp respectively. Naturally it sounds marvellous, producing all the requisite farts and crackles on the overrun, while its deep, throaty low-end rumble quickly builds into a sonorous snarl as the revs increase. As in the other three machines, it's hitched to an eight-speed automatic box (Audi's seven-speed dual-clutch transmission simply can't handle the torque), quattro permanent all-wheel drive and all manner of electronic tricks aimed at keeping car and road connected, no matter how insanely fast the former is going.
I've already said it's a monster, but in fact almost everything about the RS7 is enormous. It measures more than 5 metres long and almost 2 metres wide. Its carbon-ceramic discs, which look bigger than the wheels on some cars, are so relentlessly and reassuringly powerful they feel capable of standing the Audi on its nose whenever I stamp on the brake pedal – which is just as well, considering the speeds it can achieve. And its massive tyres provide virtually endless grip that, along with the Sport differential's torque vectoring and the battery of electronic driver aids, means it'll take you safely around just about any corner no matter how stupidly fast you enter it – even on the wettest days a tropical summer can throw at it. Like the McLaren I wrote about last month, the RS flatters your driving abilities outrageously.
By this time I've begun fiddling with the Drive Select controller, switching between Comfort, Auto and Dynamic modes – which thus remaps the engine, gearbox, dampers and steering settings – but never quite finding the perfect pre-set combination. Dynamic, for example, means instant powertrain response, glorious noises from the engine and exhaust, and an almost total absence of body roll, but a ride so harsh that it quickly becomes unbearable. (It's worth noting here that standard RS7s are equipped with air suspension rather than steel springs, which could well be the way to go if comfort is a priority.) Fortunately a fourth option enables you to dial in a personalised menu, which for me means softer damping and steering but more hard-core settings for the engine and transmission.
Thus set up, the car is staggeringly quick, beautifully balanced and surprisingly comfortable. The main issues concern the steering, which though light and quick is characteristically lacking in road feel, even when Dynamic mode is selected, and a tendency towards understeer on the twisty bits. The automatic box is perhaps a mite slow to shift, too. But when the road opens out into long straights and sweeping curves the RS7 has few peers, its immense speed and agility making it virtually unbeatable as it gobbles up huge chunks of landscape. I know which wheels will top my wish list when next I undertake a long European journey.
Naturally there are plenty of visual clues to the RS7's heroic abilities, from the black honeycomb that adorns the central grille and flanking air intakes, the five-spoke 21-inch wheels, the side sills and rear diffuser, to the body-hugging Super Sports seats, aluminium pedals, carbon-fibre inlay on the dash and console, and red seatbelts that are in vivid contrast to the otherwise inky interior. Yet as this, after all, is an Audi, everything is beautifully executed, whether it's the understated purity of the original A7 body shape or the quality of the cabin, whose layout, ergonomics and detailing – the 3D-effect instrument display, with super-legible speedo and tach raised and angled towards the driver; the honeycomb stitching on the quilted Valcona leather seats – remain in a class of their own.
As the test car is fully loaded, it also comes with a brilliant 15-speaker B&O sound system, with two acoustic lenses that appear out of the top of the dashboard like mini radar dishes, and Bluetooth connections to smartphones and other devices through the MMI interface. The sat-nav works, too, and having recently surrendered five points on my driving licence I find the head-up display a boon.
Whether I'd want an RS7 in my garage is not so easy. I've a suspicion that an M6 or a Panamera (the latter's considerable aesthetic shortcomings excepted) offer the more involving and ultimately the more rewarding drive, though I'd doubt that either offers such awesome continent-crunching abilities as the Audi. Indeed, the RS is so mind-warpingly fast, so madly extreme and so brilliantly able to shift four people and their possessions at missile velocities that I can't help but love it – but as I don't need to annihilate entire autobahns in a single afternoon I'd probably, reluctantly, have to pass. If ever I do, though, you'll know which key I'd be reaching for.