Overview: Audi RS 5
Audi is set to launch its RS 5, spiritual heir to the iconic Quattro, on the 30th anniversary of the original car’s début.
The new coupé features a formidable 450PS V8 FSI petrol engine driving through the latest incarnation of the quattro four-wheel drive system. Development work was carried out by Audi’s high performance engineering and styling subsidiary Quattro GmbH. The car’s lineage goes back 15 years to the RS 2 Avant, and indirectly to the original Ur Quattro, launched in Geneva in March, 1980.
There’s a direct link, too, to the R8 sports car. The R8’s V10 FSI engine provides the basis for the new hand-built 4.2-litre V8 FSI engine used in the new car. The 4.2 has been set up primarily to be free-revving, hitting its power peak (and the red line) at 8250rpm. Maximum power is 450PS; the torque curve peaks at 430Nm, which is available between 4,000 and 6,000rpm. At 1725kg, the RS 5 is no featherweight, but 0-100km/h in 4.6s should be quick enough for anyone. The maximum speed is electronically governed to 155mph.
Fine-tuning of the dual-branch intake and exhaust system has been aimed at boosting gas-flow at high crankshaft speeds. All four camshafts have variable timing, and tumble flaps in the intake manifold improve mixture turbulence. The unit features an on-demand electric oil pump to cut parasitic engine loads, and there’s an energy-recovery system that operates during coasting and braking. An overall fuel consumption figure of 26.2mpg (10.8l/100km) is quoted.
The RS 5’s transmission is an automated twin-clutch seven-speeder, a reinforced version of Audi’s S-Tronic unit. It consists of two clutches and two subsidiary gearboxes. Both geartrains are continuously engaged, but only one is connected into the driveline at any given time by its clutch. Gears are shifted by the disengagement of one clutch and the immediate engagement of the other, to which the next gear is already connected.
The S-Tronic can change gear automatically, or the driver can take control of gearchanging using the selector lever or shift paddles on the steering wheel. With the gearbox operating automatically, the driver can switch between ‘comfort’ and ‘dynamic’ shift patterns, or set the system to make up its own mind according to how the car is being driven. Additionally, there is a ‘launch control’ mode, in which the transmission ensures clean acceleration from a standstill at full power and with minimal losses in traction.
All Audi RS models feature ‘quattro’ permanent four-wheel drive, but this evocative word has been used as an umbrella term for a lot of different systems over the years. The RS 5 has evolved a little from its siblings in its use of a self-locking crown-gear centre differential.
This is a compact and lightweight unit, and low internal losses are claimed. The differential can vary widely the distribution of torque between the front and rear axles. The nominal torque-split is 40:60 front:rear, but the split can be varied between limits of 70:30 and 15:85. Handling balance should, within reasonable limits and if the differential reacts quickly enough, respond well to changes in road conditions, cornering loads and drivetrain torque.
The RS’s new differential works in conjunction with electronic torque vectoring. This directs torque to each of the wheels individually. If one of the inside wheels in a turn loses traction, the system slightly decelerates the wheel to prevent wheel-spin. This improves cornering traction on the one hand, while also generating a yaw moment which aids cornering.
The rear axle also features Audi’s sport differential, which distributes torque between the rear wheels.
Dynamic Ride Control (DRC)
The RS 5 adopts the latest version of Audi’s Dynamic Ride Control system, as used on the RS 6. DRC connects each wheel damper to its diagonal counterpart by way of a central valve. This directs oil pressure to the more heavily loaded damper to increase damping force, promising gains in handling precision and stability. Using the car’s Drive Select system, the driver can choose from three damper settings: comfort, dynamic and sport.
With its own specifications for springs, dampers and anti-roll bars, the RS 5 chassis sits 20mm lower than that of the Audi A5. Wheels are 19-inch alloys shod with 265/35 tyres. Twenty-inch wheels with 275/30 tyres are available at extra cost.
Stopping the RS 5 is taken care of by internally ventilated discs — 365mm in diameter at the front. To improve heat dissipation, the steel friction rings are perforated and connected by pins to the aluminium brake discs. Aluminium calipers are used; the front units are fitted with eight pistons each. As an optional extra, 380mm ceramic carbon-fibre brake discs can be specified. They are light, strong, and durable, and they’re also less prone to distort after extreme use.
The RS’s Electronic Stabilisation Program (ESP) incorporates a sport mode, and can also be switched off entirely.
Audi’s Drive Select vehicle dynamics control system is a standard feature of the RS 5. It allows the driver to adjust the steering weighting, the shift points for the gearbox, the sport differential, Dynamic Ride Control, the engine and the exhaust system. There are two fixed modes — comfort and dynamic — plus an automatic mode that chooses the systems settings according to how the car is being driven. If the car is equipped with the optional navigation system, a fourth mode allows the driver to customise their own profile.
Amusingly, Audi has incorporated into the engine a system for making it sound more impressive ‘for maximum enjoyment of the engine’. The Drive Select system controls two throttle valves and ‘sound flaps’ in the exhaust system. When these flaps open, the engine note becomes more resonant. An optional Sport exhaust system which is claimed to offer an even more bass-heavy sound is available at extra cost. Lawdy.
The Drive Select system is set up to allow for variable ratio steering, although this function will not be standard. Called ‘dynamic steering’, the optional system adjusts the steering ratio according to the car’s speed, using more direct ratios for low-speed manoeuvring and lower ratios for motorway driving. At the vehicle’s cornering limits, the dynamic steering system provides minor corrective actions to help smooth out the handling. Like many aspects of electronic control over vehicle dynamics, this idea will perhaps take a little getting used to.
The RS 5’s styling differs in detail from its cheaper siblings. There’s an extensible rear spoiler that automatically deploys at 75mph and retracts at 50mph. We take this to mean that it doesn’t serve any useful purpose below 75mph. We wonder whether Audi will do to the RS 5 what Porsche did to the 911 many years ago and reset the spoiler’s deployment speed for the U.K. market, rendering it (on home turf) a vanity accessory.
The underbody of the RS 5 has aerodynamic cladding, with air vents for the S-Tronic transmission and for the front brakes. At motorway speeds, the aerodynamic characteristics of the RS 5 generate downforce — still something of a rarity, even among sportscars.
Audi is now taking orders from U.K. customers. The on-the-road price is £57,480, and deliveries will begin in October.