For even more performance, Audi offers limited-production RS 4 versions of the S4 sedan and cabriolet. The main difference is the retuned V-8 engine with the same 4.2-liter displacement that is now capable of 420 horsepower (an improvement of 80 horsepower over the S4) with a redline of 8,250 rpm. There is also a sport mode on the RS 4 that changes throttle input for a sportier driving experience and audibly changes the tone of the exhaust for a more imposing sound. Improving the stability, the RS 4 rides on a wider track than the S4 and refines the sport handling capabilities with further tuning to the suspension components. The RS 4 uses flared wheel arches, aggressive front fascia with added air inlets and unique 19-inch wheels to build on the S4’s already aggressive look and stance. Since the RS 4 has a primary purpose of being a track car, the driver’s information display also has a stopwatch feature with lap timer function.