As with the saloon and Avant, the ride height of the Cabriolet has been lowered by 30 millimetres compared with the A4 Cabriolet. This emphasises the car's sporty appearance.
Even if the Audi Cabriolet's weight has been rigorously trimmed down, in common with all other RS 4 models no corners have been cut with either its equipment or its standards of safety.
The further improved crash strength of the latest A4 Cabriolet generation has likewise benefited the open-top RS 4. The front and side airbags are standard features, as are the rollover bars that extend behind the rear seats in the event of the car overturning.
The 420PS V8 revs up to a speed of 8,250 rpm. With its displacement of 4,163 cm3, this outstanding engine breaks through the magic barrier for a production saloon of 100 bhp per litre. The highly compact power unit reaches its peak torque of 430 Nm at 5,500 rpm. At least 90 per cent of the maximum torque is available between 2,250 and 7,600 rpm. The result is excellent pulling power at all times, enabling the driver to drive in a relaxed style without frequent gear changes.
Audi's RS 4 saloon employs groundbreaking FSI technology. The petrol direct-injection unit delivers enhanced power output based on more efficient combustion of the fuel/air mixture. The engine is also more responsive. The performance of the RS 4 clearly demonstrates this progress: it reaches the 100 km/h mark in 4.8 seconds (Avant 4.9 seconds, Cabriolet 4.9 seconds), and 200 km/h in 16.6 seconds (16.9 seconds; 17.5 seconds). On all three versions, the speed is governed electronically when the needle reaches 250 km/h.
Audi has deployed the high-revving engine principle for the first time in the RS 4. The advantages of this principle are superior power output at high engine speeds, a smooth power flow and eager responsiveness all across the revs range. Further fortes are the car's outstanding agility and fast-revving response as well as the kind of racing-style engine sound that drivers of such cars simply expect.
As a result of these qualities, the eight-cylinder power unit provides maximum thrust and performance in virtually all driving situations. The constant flow of power from bottom-end speeds all the way up to 8,250 rpm is equally appropriate for a relaxing driving style with minimum gearshifting and for exploits worthy of the racetrack.
The V8 power unit is ultra-compact in its dimensions, fitting snugly into the engine compartment of the RS 4 without necessitating any modifications to the body. The camshaft and ancillaries, with the exception of the alternator, are all driven by a chain for easy maintenance. An all-new development, the eight-cylinder unit powering the RS 4 includes such features as modified pistons and con rods, a new crankshaft together with its bearings, and new cylinder heads.
A dual-branch exhaust system with enlarged pipes provides even higher power output. These extensive measures have enabled the 4,163 cm3 engine to break through the magical 100PS per litre barrier.
The car's power-to-weight ratio is also impressive: 254PS per tonne is a figure that only the most thoroughbred sports cars were able to offer just a few years ago. The figure for the Avant is only slightly higher.