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by Greg Kable 13 November 2019 Follow @@autocar Share
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The engineering brief for the new Audi S8 is surely one of the most demanding in the automotive business.
Here’s a car that, on the one hand, must deliver top shelf limousine like qualities, with all the imbibing plushness, soft-riding comfort and soul soothing refinement discerning customers expect.
As effective as it is under full load in sport mode, the S8’s engine is also compellingly smooth on more measured throttle inputs in an altogether more relaxed Comfort+Greg KableEuropean editor
But at the same time, the most outwardly sporting variant of Ingolstadt’s flagship four-door saloon is also expected to offer supercar-like performance while engaging the driver with the sort of dynamic qualities to see off its premium brand rivals – all in a package stretching to over five metres in length and weighing all of 2230kg.
It’s a balancing act previous incarnations of the S8 attempted to achieve but arguably failed to pull off with quite the same level of success as the high end competition.
For this new one, Audi has left nothing to chance. Not only does the new S8 get a heavily reworked twin-turbocharged 4.0-litre V8 petrol engine featuring new mild hybrid properties but also the most advanced suspension Audi has ever placed in a production model.
With 563bhp, power has wound back by 34bhp over the ultimate version of the third-generation S8 – the S8 Plus, which used a less heavily developed version of the same engine. But with up to 1.8bar of turbocharger boost pressure, torque has increased by 37lb ft, now peaking at 590lb ft on a band of revs between 2000 and 4500rpm.
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To put this into perspective, the newly facelifted BMW M750i xDrive’s twin-turbocharged 4.4-litre V8 petrol engine delivers 523bhp and 553lb ft, while the Mercedes-Benz S63’s twin-turbocharged 4.0-litre V8 powerplant serves up 603bhp and 664lb ft.
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The stronger reserves are sent through an upgraded eight-speed torque converter equipped automatic gearbox with a manual shifting Tiptronic function and Audi’s quattro four-wheel drive system with a so-called sport differential that constantly varies the amount of drive sent to each individual rear wheel. Depending on the conditions, up to 70 per cent of drive can be delivered to the front wheels. Alternatively, 85 per cent can also be apportioned to the rear wheels.
Audi makes big claims about the new S8’s efficiency. It boasts both a cylinder on-demand system that automatically closes down one bank of cylinders on light throttle loads at urban driving speeds and a new belt-driven 48-volt starter motor that operates in combination with a 0.47kWh lithium-ion battery and a recuperation system capable of harvesting up to 8kW of energy during braking and coasting. Together, they are claimed to reduce consumption by almost 0.2mpg.
Yet despite the impressive energy-saving technology, combined cycle fuel economy is reduced from a previous 29.4mpg to 24.8mpg, giving the new S8 an average CO2 rating on the NEDC cycle of 260g/km.
It’s the suspension, though, that Audi is relying on to allow the new S8 to successfully achieve it dual roles. The new system, known as Predictive Active Suspension, uses a camera to scan the road and electro-mechanical actuators to constantly vary the ride height. Each wheel can be separately loaded or relieved depending on the road conditions across five driving modes. In Comfort+, the suspension tilts the body into corners to reduce lateral forces. In Dynamic, body roll is reduced to around half of that of a standard steel sprung suspension, according to Audi.
As always, there’s little to tell the fourth-generation S8 apart from its less sporting A8 sibling. Audi has a long history of delivering some of the most sought after understated performance saloons, and it is successfully employed here. At standstill, the new model looks pumped but subtly so and without any obviously contrived design elements. Among the unique touches is a new front bumper housing an S8 specific double louvre grille, wider sills beneath the doors, aluminium-look mirror housings and Audi’s signature S-model quad tailpipe treatment at the rear.