Twin Turbo V-10 Audi RS 6 Quattro

How much more power can a compact sedan or wagon have? 500 bhp seemed to be the limit, but Audi has raced through that with the amazing Audi RS 6 Quattro. Powered by Audi's version of the Lamborghini V-10, the RS6 blasts to 60 mph in 4.5 seconds, and to 125 mph in 15 seconds.

This takes a fairly smooth, but nevertheless ordinary looking car into the supercar class. It is not just the speed alone that takes the Audi RS 6 Quattro into this select band, but the new Quattro system and ingenious suspension.

Eyebrows over the wheels which are big with low-profile tires - and the two big exhaust pipes show that this is no ordinary A6, but to a quick glance this is just one more ordinary wagon or sedan. The rear end has a sloping under tray to get the air away.

Twin-turbo V-10 engine for torque and power

Even so, it is the 5.2 liter engine that sets this car apart. Audi has been using its direct injection version of the V-10 for a little while now, but for the new RS 6 Quattro, twin turbochargers, designed to give power throughout the speed range have been adopted. The result is a stunning 570 bhp at 6,250 rpm, while the torque is a massive 480 lb ft (650 Nm) over the whole speed range of 1,500 rpm to 6,250 rpm!

This terrific speed range over which you get maximum pulling power means that there is plenty of turbo power on tap at almost any speed.

There is just the one transmission available – a slush-box automatic with Tiptronic control, through a pair of paddles at the steering wheel. So you will never be stuck for power because as soon as you put our foot down the box will find you the ratio you want.

40:60 torque split and cross-linked damping

For years, Audi stuck with a 50:50 front to rear torque split on its Quattro cars, but recently it has improved the handling by raissing the power toward the rear, and the RS6 Quattro gets that too 40 per cent of torque goes to the front wheels and 60 per cent goes to the back wheels.

As the rear is a lot lighter than the front, this arrangement makes it easier to slide the tail out under power. To allow this, the threshold of the stability control has been set to allow more slippage. It can also be switched off.

The Audi A6 has the right underpinning for a performance are with double wishbone front and multi-link rear suspension supplemented by anti-roll bars. For the RS6 Quattro, stiffer springs are used.

Also, Audi has adopted its cross-linked damping system, in which the dampers are connected to a central set of valves. When a damper is compressed, extra fluid is sent to it from the damper diagonally opposite that is from front-left to rear-right and so on, which improves handling.

This system can also be set to three settings by the driver comfort, dynamic and sport. Roll is less than with a conventional system, but the ride is as good as normal.

Obviously, the brakes are large there is an option of carbon-ceramic discs - and so are the wheels ad tires 19 inch wheels are standard but there is the option of 20-inch wheels.

To give plenty of grip when you start pushing the car, the seats are trimmed in Alcantara, rather than potentially slippery leather, which can spoil the comfort when cornering fast in many a supercar. You also get full instrumentation with the Audi RS 6 Quattro and a fashionable flat-bottomed steering wheel. To reduce weight, the front fenders and hood are use aluminium.