Audi's new RS4 quattro four-door sedan steps boldly into supercar territory with 0-100km/h acceleration of under five seconds and the potential to hit 290km/h flat-out.
It's being seen as the most dramatic Audi since the original quattro coupe of 1980. That car sprinted to 100km/h in a shade under seven seconds, and started the revolution that has seen four-wheel drive turbocars dominate the World Rally Championship.
The 2005 RS4, which debuted at this month's Geneva motor show in Switzerland, differs from the original quattro and subsequent Audi performance cars in one major respect.
In place of a turbocharged motor, it runs an all-new 4.2-litre FSI direct petrol injection V8, derived from the 90-degree unit used in the Audi S4.
The V8 delivers 420bhp and peak torque of 430Nm.
Though the peak occurs at 5500rpm, 90 percent of the torque is available between 2250rpm and 7600rpm.
Audi quotes a 0-100km/h time of 4.8 seconds, and says the RS4 will reach 200km/h in around 16.6 seconds.
It has an electronically limited top speed of 250m/h but if it allowed to run unrestricted to the 8250rpm redline the RS4 would hit 290km/h-plus.
Audi developed FSI direct petrol injection in the Audi R8 Le Mans V8 sports racing cars before using it in four and six-cylinder road cars.
This is its first application in a road-going Audi V8.
Audi says the system helps maximise both performance and efficiency through more effective and accurate fuel combustion.
A steering wheel-mounted Sports button enables the driver to adjust the throttle control mapping to give even sharper response.
The RS4's Electronic Stability Programme (ESP) has been programmed to intervene later and for a shorter period than in a standard A4, improving driving satisfaction while retaining traction.
Careful design to keep weight to the minimum has given the new RS4 an impressive power-to-weight ratio of 254bhp per tonne (that compares with the BMW M3's 215bhp/tonne).
The RS4 uses aluminium for normally heavy items like the suspension, bonnet and front fenders.
The car is 30mm lower than a standard A4, and has wider front and rear track.
To give it more of a driver's car feel, a new evolution of the quattro four-wheel drive system does away with the traditional 50/50, front/rear, torque split. In the new RS4 it delivers 60 percent of torque to the rear wheels, making the car more agile - at the expense of some traction - and making its cornering behaviour more adjustable.
The system works in conjunction with Dynamic Ride Control, an electronically governed, mechanical damping system. DRC connects the car's shock absorbers diagonally, using a central valve which directs a flow of oil to provide additional damping force whenever a shock absorber is compressed. That improves handling precision and the car's stability.
The RS4's 19-inch alloy wheels surround 18-inch disc brakes.
Details like a tapered sports-style steering wheel, RS bucket seats, engine starter button and extensive carbon fibre trim give the RS4 a race car feel.
Audi will sell saloon and Avant station wagon versions of the RS4, the Avant from 2006.
British magazine Autocar says the RS4 is the first of several naturally-aspirated Audi performance cars, including an RS6 and an RS8.