Spy shots of the upcoming 2018 Audi RS5 test mule have been captured as it undergoes development work. Recently, it was revealed that the new Audi A5 and S5 models will go on sale as early as September of this year. This leaves the top of the range RS5 model as the only model yet to receive a release date from Audi. The RS5 is expected to be powered a turbocharged V6 engine with total output around 420 to 450 horsepower.