WHEN IS a V8 not a V8? Audi has the answer in its latest range of S cars, which aren’t just ridiculously quick and lavish: they’re also cleverly efficient.
Everything is relative of course, and nobody’s saying that the S6 and broadly similar S7 are Greenpeace’s new mascots. But under their bonnets, inside the advanced new 4.0-litre V8 they share, is a cylinder-deactivation system that cuts fuel to four cylinders when they’re not needed, turning the unit into a 2.0-litre V4.
The S6 Avant we have here is arguably the most practical among the S6 and S7 range, despite the S7’s thoroughly capacious hatchback boot.
You’ll find roughly the same engine in the Bentley Continental GT V8, so rest assured it’s a belter. No Audi S model has ever been lacking in the power department, and with 414bhp it’s as powerful as past RS-badged cars.
Now, as Peter Parker was once told by his uncle in the film Spiderman, ‘with great power comes great environmental responsibility.’ Or something along those lines, anyway.
So to balance out the immense shove that’s distributed to all four wheels, the cylinder deactivation system helps the car achieve 29.1mpg, 0.3mpg less than the 55kg lighter saloon but still remarkable for a vehicle that hits 62mph in 4.7 seconds.
Alas, there’s a spanner in the works with CO2 emissions of 226g/km, adding just one gram to the saloon’s figure but dumping £190 onto the tax bill, making it £460 per year instead of £270. The extra practicality of the Avant will no doubt make it a worthwhile investment to some.
Matching the S6 platform’s astonishing performance is an array of electronics and computing power that would have baffled scientists 15 years ago, let alone the men who put Neil Armstrong on the moon.
Some of it is optional, but Audi is hailing an adaptive cruise control system as the highlight. It’s capable of controlling the car’s speed anywhere between 0mph and the car’s 155mph limited top speed using a pair of forward-facing radar sensors, albeit with limits attached to how hard it will brake without driver input.
In the real world only an emergency stop situation would demand harder braking, and it works unnervingly well – if you can allow yourself to trust it. There are other caveats and occasions when it deactivates though, and unfortunately it’s not a system you can just use fully without reading the manual.
The same goes for much of the MMI system, which when you know how to get to what you need is efficient and stylishly designed. But it’s so full of menus, settings and bizarre why-would-you-need-it options that at times it’s its own worst enemy.
Under more traditional scrutiny, as in that of how well it drives, the S6 is almost, almost brilliant. The huge and relentless acceleration through the seven-speed auto gearbox is matched by monumental braking power, all the grip any sane person could ever need and a more than pleasant V8 rumble from up front.
Its Achilles’ heel is its steering, which isn’t just variable assistance but is variable rate, too, steering more for a given wheel movement the faster you travel. The problem comes when you turn into a corner expecting to need to turn the wheel a certain amount, only to discover the car disagrees and doesn’t steer enough. It feels almost like understeer behind the wheel, but it’s technically very different.
But to be fair it’s a rare occurrence, especially when you’re used to it. Call it a quirk, which is a rare thing on an Audi. The vast majority of the time the steering is accurate, direct enough and well matched to the chassis dynamics – which, of course, can be altered as part of a drive mode sub-menu.
As well as big performance stats the other key box a fast Audi estate needs to tick is interior luxury, and I guarantee no disappointment on that front. The materials are thick and plush, the styling and layout is mostly very good, the instrument cluster is attractive and upmarket, and the seats are supportive.
Past bugbears about Audi ride quality were not at the time unfounded, but improvements have definitely been made. On optional 20-inch wheels the S6 rides relatively well, and much better than even 18- or 19-inch equipped Audis of recent memory. It only gets really crashy or unsettled on the worst of rural roads.
Of course, the interior space is immense. The boot is gargantuan, and luckily special fixings to stop loads sliding around are standard fit. Rear legroom behind a six-foot driver is ample, although the chunky front seat bases do prevent rear passengers tucking their feet underneath.
There are certain things that a fast Audi should be, and some would argue an Avant is one of them. Very fast is another, and by Jove the S6 is that as well. It’s also comfortable, luxurious and massively advanced. If you like fast Audis, you’ll love the S6 Avant.
FACTS AT A GLANCE
Model: Audi S6 Avant, £56,050 on the road.Engine: 4.0-litre turbocharged petrol V8 producing 414bhp and 406lb.ft.Transmission: 7-speed automatic gearbox driving all four wheels.Performance: Top speed 155mph, 0-62mph in 4.7 seconds.Fuel economy: 29.1mpg.CO2 rating: 226g/km.