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New Audi S models to feature new downsized 4.0L V8 with cylinder deactivation, energy recuperation and start-stop

31 August 2011

Audi will present its new S models for the first time at the 2011 Frankfurt Auto Show (IAA). The new S6, S7 and S8 feature a new 4.0L TFSI V8 with cylinder deactivation (cylinder-on-demand), energy recuperation and start-stop system). This is a downsized platform from the prior 5.2L naturally aspirated V10.

The S6 and S6 Avant use the 309 kW (420 hp) version of the new 4.0 TFSI. The twin-turbo V8 provides a constant 550 N·m (406 lb-ft) of torque from 1,400 to 5,300 rpm. It accelerates the S6 from 0 to 100 km/h (62 mph) in 4.8 seconds and the S6 Avant in 4.9 seconds. Both models have an electronically governed top speed of 250 km/h (155 mph).

Compared to the 5.2L V10 engine in the previous model, the 4.0L turbo reduces fuel consumption by as much as 25% percent. Average fuel consumption is 9.7 liters per 100 km (24.3 mpg US) in the S6 and 9.8 liters (24.0 mpg US) in the S6 Avant.

A number of technologies contribute to this top result, including the energy recuperation and start-stop systems as well as the new cylinder-on-demand cylinder management system. When the V8 deactivates four cylinders under part load, the Active Noise Cancellation system (ANC) is activated. Four microphones integrated into the headlining record the noise in the cabin, which is then analyzed by a computer. If the computer detects intrusive sound elements, it broadcasts an antiphase sound through the speakers of the sound system. This sound combines with the intrusive sound and largely cancels it out.

Independent of this, active, electronically controlled engine bearings use targeted counterpulses to attenuate low-frequency vibrations. A sound actuator, flaps in the exhaust system, the engine shroud and a newly developed two-mass flywheel with a centrifugal force pendulum in the seven-speed S tronic also contribute to the sound and smoothness of the engine.

The Audi S7 uses the same engine as the S6 and S6 Avant, with fuel consumption of 9.7 liters of fuel per 100 km (24.25 mpg US). The S7 features a lightweight body of a hybrid aluminum construction, weighing roughly 15% less than a comparable all-steel body.

The Audi S8, which will be launched on the market in spring 2012, features a new 4.0 TFSI which generates 382 kW (520 hp) and delivers a constant 650 N·m (479 lb-ft) of torque to the crankshaft between 1,700 and 5,500 rpm. Acceleration from zero to 100 km/h (62 mph) takes 4.2 seconds, and top speed is electronically capped at 250 km/h (155 mph).

Fuel consumption averages 10.2 liters per 100 km (23.06 mpg US), a decrease of nearly 23% despite a 51 kW increase in output compared to the preceding 5.2L V10. The new S8 also features cylinder-on-demand, recuperation and start-stop systems.

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Major gas guzzlers?

Relative to the 50 mpg diesel models, yes, but remember that a very small fraction of the market will only buy the S4 due to price and horrific depreciation - more horrific than the extra running costs due to fuel consumption.

Meaning the second owners will get a few-year-old guzzler relatively cheaply. Better that the guzzlers weren't made in the first place; luxo models should be required to be PHEV by law. Let the rich buy the battery packs and pass them along, subsidizing the lower-income buyers and cutting fuel use every step of the way.

But then that's the point, they become much cheaper because no-one wants to buy a car that uses a lot of fuel, except enthusiasts who will spend more time polishing them, taking them out on the odd weekend run and use a daily-driver runabout that's cheaper to run or even "shock-horror" take the bus.

I wouldn't have one myself, but I don't think a small minority of people who buy something for a weekend hobby is going to make the earth implode, which kind of makes people's knee-jerk reactions a bit over-reactive.

...but then I wouldn't fancy a hybrid or electric either given that their efficiency is overshadowed by the issue of replacing batteries - £20,000 for a set for the leaf (if you haven't got fed up with the short range by then). And given what's been said about the overall lifecycle costs, the efficiency benefits seem to be pretty marginal. Personally, i'd rather go for a clean burning diesel that gets 50+mpg on its combined cycle: efficient, long range and no hidden surprises with long-term bettery drain.

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