At the Geneva Motor Show last month, we got a glimpse at a new 2018 Audi coupe. Audi says the 2018 RS 5 Coupe will focus on both performance and fuel efficiency. It will be powered by a new twin-turbo 2.9-liter V6 rated at 450 horsepower and 442 lb-ft of torque. This engine replaces the 4.2-liter V8 in the outgoing model, making the new coupe lighter. The V6 is paired with a Tiptronic eight-speed transmission and Audi Quattro all-wheel-drive system….