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Does the buyer spending $200,000 on a high performance saloon really want to be this subtle?

WITH Audi’s new S6, superlatives don’t necessarily spring to mind. Rather, you’re left with a sort of delighted puzzlement.

The new flagship for Audi’s mid-size range isn’t the maxi-G, rocket-thrusting, thumping twin-turbo that was the previous RS6. And it’s not simply a deliciously accelerative car that’s more a luxury sedan than sports sedan. Somehow it treads a thin line between the two.

The S6 certainly has mind-altering credentials: An all-alloy, direct-injection 5.2-litre V10 producing 320kW along with a surging, non-turbo 540Nm of torque is enough to have one thinking about unrestrained, over-muscled, riotous on-road behaviour.

This is an engine bigger than the stupendous BMW M5’s 5.0-litre V10.

Okay, it doesn’t produce the same power (the M5 makes an astounding 373kW), but it has more torque (540Nm compared with 520Nm), and promises even better ability to get it to the ground, with full-time four-wheel drive delivering the traction that such power demands.

The Lamborghini-derived powerplant is a snug fit in the Audi’s engine bay – something the company seems to enjoy doing, if the blistering RS4 V8 is any indication – and there’s certainly not a lot of breathing space between the four-ringed grille and the front of the V10.

But there is never a thought of imbalance. Weighing just 220kg, the V10 is lighter by 20kg than the already wispy M5 engine, meaning the distribution of mass between front and rear is less of a problem than by rights it should be.

But the close-to-$200,000 car is so distant from regular A6 models – that start with a 2.0-litre turbo front-drive four-cylinder costing not much more than a third of the S6’s price – that you’d barely connect them.

The specification, from the equipment to the running gear, is all you’d expect.

Eight airbags are provided, along with whiplash-minimising front seats. There’s a tyre pressure monitor even though the S6 runs a full-size spare, front and rear park-distance sensors, bi-Xenon headlights, satellite navigation with TV, a sunroof and a mood-setting 13-speaker Bose AM/FM audio with a six-disc CD player in the glove box.

The short options list includes things like adaptive cruise control, adaptive headlights, a reversing camera and a solar sunroof.

The S6 joins its larger, and identically engined S8 sibling – although the bigger, aluminium-bodied car produces more power (331kW), meaning it’s actually a bit faster – as a showcase for the V10, which has clear potential for more and brings thoughts of a future RS6 model. A smaller-bore, 5.0-litre 382kW version of the same engine can be found in the Lamborghini Gallardo Spyder.

It doesn’t exactly bristle with high technology (no variable valve lift, for example), but it does get common rail direct injection, a super-high 12.5:1 compression ratio, variable-timing camshafts, a balancing shaft, two-stage variable intake manifold and rear-of-engine chains driving camshafts, oil and water pumps and auxiliaries.

The V10 drives through Audi’s familiar six-speed tiptronic automatic transmission – using a different set of ratios to the A6 – to the quattro three-differential all wheel drive system that electronically apportions power delivery to the point that as much as 85 per cent of power can be channelled to the back wheels (or 65 per cent to the front wheels) when the occasion demands.

The coil-spring suspension has been reworked accordingly, and the wheels are up to 19 inches in diameter wearing symmetrical 265/35R19 tyres at both front and rear.

But when you start looking more deeply into the specifications and discover that the Audi V10 is not just less endowed with kilowatts than the BMW V10, but also weighs quite a bit more, you begin to understand why the S6 lacks the anticipated animal attitude.

Two tonnes loom with a quoted kerb weight of 1910kg, which is a solid 155kg more than the M5 and barely any less than the aluminium-bodied S8’s 1940kg.

The result is that the S6 reaches 100km/h from a standstill in 5.2 seconds (5.1 for the S8) where the M5 takes just 4.7. The chunky RS4 V8 makes it to 100km/h in 4.9 seconds.

So, although it’s virtually as quick as a Porsche 911, the S6 is the antithesis of a raw, brutal, racetrack-oriented muscle car.

The whole experience is one of sure-footed, confident firepower. Plant the accelerator pedal and the S6 responds with a rising surge and a distant hammering from the V10 as it works its way towards the 7200rpm redline.

Although you’d never say an M5 was unrefined, the experience is altogether different in the Audi, where you’re more an observer than a wired-in, direct participant. As the scenery blurs by, you’re cosseted in a silent, stable and reassuring sense of calm.

Needless to say, the S6 feels well planted on the road, even if it absorbs the bumps with a lovely sense of compliance rather than a firm attack that forcefully reminds you of what a potent vehicle you are driving.

The steering, modified over the A6 for improved response, is quick and light to touch, almost too light for a super high-performance car – although there’s never any questioning its stability.

Driving the S6 more quietly, you’d rarely be aware – apart from a deep, growling bark when it’s fired up – of the feats it is able to perform. It is entirely tractable, deadly smooth, spacious and luxurious. With its massively deep, 546-litre boot, complete with a split-fold rear seat, it’s even practical.

The steering wheel goes from lock to lock in a minimalist 2.6 turns, although this is partly explained by the turning circle which is a less than wieldy 11.9 metres (better than the M5’s 12.4 metres though).

An interesting thing about this 5.2-litre V10 is that it does a pretty good job of conserving fuel. On test we averaged between 11.0L and 12.0L/100km, which is not bad for a potent two-tonne sedan. A firm foot would produce worse results without trying too hard though, and obviously this high-compression powerplant does require premium unleaded fuel.

With its more-than-subtle external changes, identification of the S6 is largely left to the 19-inch wheels and subtle but affirmative embellishments like the slightly flared wheel arches, wider side trim strips and the subtlest of rear spoilers.

Of course there are the V10 badges on the flanks, and the S6 badges set into the single-framer grille and on the boot, as well as LED daytime running lights sitting low in the front apron, along with the tell-tale quad exhausts.

If you’re one of those drivers with no need to flaunt, high performance doesn’t come any more discreet than in the Audi S6.