The new S8 is one of the quartet of new Audis powered by the Ingolstadt firm’s 4.0-litre V8 with cylinder-shutdown technology. But has driving pleasure been switched off in the process? We take the powerhouse for a spin to find out.
When Audi first launched the then 335bhp S8 in 1996, it caused senior managers at Stuttgart and Munich a few sleepless nights. The most recent version - with its 5.2-litre V10 from the R8 - piled on the pressure. Now that the S8 has lost two cylinders and adopted more conservative looks, has it become a tame boulevard cruiser, and lost its 'fast limousine' crown to BMW or Mercedes?
Far from it. Despite downsizing, the thunderous new flagship (of the four-ringed saloons at least) can trounce pretty much anything currently available in the luxury sports saloon market.
The completely redesigned, all-alloy, 4.0-litre twin-turbo V8 engine plays a significant part in this. The direct-injection unit is the very same that will be slotted neatly into the Bentley Continental GT and GTC next year, conjuring up 513bhp and 479lb ft of torque. That means it surpasses its already potent V10 predecessor by almost 70bhp.
It’s not just the power which has vastly improved. Fuel economy is superior as well, chiefly due to cylinder-shutdown technology which has also been adopted by other marques in the Volkswagen Automotive Group, as well as Mercedes. By adjusting the camshaft timing, and cutting the ignition and fuel supply to cylinders 2, 3, 5 and 8, the new system allows the S8 to go from a V8 to a V4 under deceleration and low throttle input.
But those who buy a V8 want to drive a V8, not a V4. Audi recognises this and, as a result, has developed a system which compensates for any negative (sound and vibration) characteristics. Mounted in the headlining, four directional microphones process interior sound levels in real-time, eliminating any annoying 'hum' frequencies by sending out a counteracting sound via the multimedia speakers.
Active engine mounts also soak up the vibrations produced in V4 mode, both systems effectively compensating for the possible vibrations of a quad-cylinder engine.
Realistically, though, what’s most important is how the S8 performs on the road. After covering only a few kilometres in the pre-production example we tested, it’s clear that the three years of development have paid off. Planting the accelerator makes the 4WD Audi launch itself towards the horizon in a way never seen before in an S-model.
Gone, though, are the days when even a cautious squeeze of the pedal was punished by an impromptu meeting with the rear bumper of the car in front - the new S8's power delivery has the characteristics of a thick rubber band, and at full throttle it simply demotes other road users to ‘extras’.
The new S8 can also be a humble beast, quickly demonstrated in a steady flow of traffic. As soon as the electronics detect more sedate driving behaviour (and thus the chance to save fuel), four cylinders are put to sleep. The switching process takes 300 milliseconds and, due to the measures already described, the only way the driver will know is through the illumination of a green light in the instrument binnacle. There is no stuttering or acoustic change during the complex process, and the thunderous power of full-fat V8 mode is instantly accessible.
Audi promises a reduction in consumption of around 23 per cent compared with its V10 predecessor. However, the stop-start and recuperation systems – combined with a smaller capacity – contribute to this more than the cylinder-shutdown technology; in isolation, it accounts for an economy advantage of around 5.5%. The combined cycle of 27.7mpg means that the new S8 is lighter on both the conscience and the bank balance, but it is also expected to keep the other 'Big Three' German manufacturers on their toes when it goes on sale in Spring 2012.
Text & Photos: Sven Jürisch
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