The A5 encompasses a wide range of performance that boils down to the numbers of cylinders under the hood. In short, the A5 itself sports a turbo four-cylinder; the S5 gets a supercharged six; and the roaring RS5 has the lineup's only naturally aspirated V-8.
As an A5, the two-door Audi relies on the corporate turbocharged 2.0-liter four for power in all versions, from front-drive Cabrio to all-wheel-drive Coupe. With 211 horsepower and 258 pound-feet of torque, the powerplant generates a wide, useful band of torque from low in its rev range, pulling strongly through about 6000 rpm as it tapers off toward redline. It's fast to respond to throttle changes even without available driver-configurable options, and though it can sound a little gritty as it winds out, it's an exemplary unit that still compares well with the newer turbo fours from Mercedes, BMW, and Cadillac.
Transmission choices depend on body style. In the Coupe, Audi brings a choice of an eight-speed automatic or a six-speed manual. Either one suits the A5 well, though with quattro all-wheel drive, the eight-speed automatic is particularly effective, since it has more gears, staged in the grunty end of the powerband, to deliver good acceleration and decisive, quick downshifts. Audi estimates 0-60 mph times with the automatic of 6.6 seconds; with the six-speed manual, it's even quicker, at 6.4 seconds.
In the Cabriolet, Audi's continuously variable transmission makes its only appearance. It's not unwelcome, especially for those seeking out its excellent city fuel economy ratings, but like other CVTs, it's more sluggish to respond and generates more drivetrain noise than a well-sorted automatic. It still suffers from a drawn-out feel, almost rubbery, as it glides through ratios generated by the expansion and contraction of pulleys around a belt--they take the place of conventional gears. This is Audi's least satisfying powertrain available in the U.S. It's the only A5 offered without all-wheel drive, and still it's the slowest of the A5 lineup, with a 0-60 mph time estimated at 7.5 seconds. Even with the weight penalty of all-wheel drive, the Cabriolet with the excellent eight-speed automatic hits 60 mph in 7.2 seconds.
Ride and handling are set for comfort, but Audi makes its Drive Select feature available on the A5. Along with the CVT, it's a feature we'd just as soon leave on the order sheet. Drive Select gives the driver the ability to alter settings for the suspension, steering, transmission and throttle response. As it does in the A4 sedan, Drive Select can be a bit of too much choice--much of the time, it doesn't seem to offer the right combination of ride and handling to suit the car's character. We think the basic suspension is up to the task, allowing you to maintain composure over choppy surfaces without feeling overly stiff. If the mostly serene driving feel of the A5 needs a boost, in your mind, there's always the S-line option package that has stiffer suspension settings and better handling. A superb ride—firm but just absorbent enough—plus excellent insulation from road and wind noise altogether make the A5 a joy for covering long distances.
Steering response, with or without Drive Select, has improved this year with the adoption of electric power steering, which in the now-typical VW/Audi mold, has better on-center feel and response than some other brands and executions. It also enables Dynamic Steering, a variable-assist feature that can change the amount of steering response delivered based on a variety of factors. It's another feature that means more to enthusiasts and higher-performance cars, than it does to more relaxed cruisers like the A5 and its drivers.
Move up to the S5, and the two-door's performance envelope expands to FedEx proportions. Both the S5 Coupe and Cabriolet are now powered by a 3.0-liter supercharged V-6, rated at 333 horsepower and 325 pound-feet of torque. Until this model year, Coupes still sported a V-8 engine. Performance hasn't lagged, though--acceleration is still good for 0-60 mph times of about 5.0 seconds. The S5 cars adopt stiffer suspensions and better brakes, and Audi's magnificent seven-speed dual-clutch transmission becomes the gearbox of choice on the coupe, above and beyond the standard six-speed manual. (Cabriolets don't offer the manual at all.) The dual-clutch's lightning-quick reflexes and paddle controls will have even the diehard shift-it-yourselfers reconsidering their position on the third pedal.
With uprated brakes, 18-inch wheels and summer sport tires, and standard all-wheel drive, handling is, as you might expect, is very good. Audi's quattro all-wheel-drive system aids this, biasing the front-rear power split at 40/60 percent, and an available sport differential splits power between the rear wheels for even more balanced handling. Electronic power steering in the S5, like everywhere it's been used, is a tad on the numb side, while the stiff ride quality which enhances handling can feel a bit harsh on the street, though the optional Drive Select system allows the driver to adjust the shift modes, suspension stiffness, and steering feel to better suit the situation. As with the A5, the S5's basic suspension seems so well-sorted, Drive Select and Dynamic Steering seem more like an upsell than a necessity. Braking performance is very good.
At the pinnacle of the A5 lineup sits the RS5. New for the 2013 model year, the coupe-only cruiser is the only model to carry a V-8. It's a muscular 4.2-liter engine with 450 horsepower that shows its semi-exotic roots as it blends power with an authoritative growl through the seven-speed dual-clutch transmission and all-wheel-drive system. Audi pegs 0-60 mph times at 4.5 seconds, and top speed rises to 174 mph, figures that rival BMW's M3 and Mercedes' C63 AMG. The sport differential comes standard, as do 19-inch wheels and Drive Select--but without control over the suspension, which uses conventional springs and shocks. Dynamic Steering remains an option on this model, too. It's the sole A5 that feels fluid with Drive Select, admittedly left in its most sporting setting, while even Comfort mode imparts a somewhat stiff ride. A sport exhaust makes the RS5's sound even more resonant, and optional carbon-ceramic brakes lift its stopping power into Porsche territory. In sum, the RS5 is part luxury coupe, part weekend track toy.