For the first time in its history, the Audi S5 now has a V6 diesel at its heart. Underpinned by mild hybrid technology, it equips the peak performer with impressive staying power between fill-ups and delivers even greater immediacy of response courtesy of an electric powered compressor. The 3.0 TDI engine, which will be introduced in both the S5 Coupé and the S5 Sportback in late 2019, now produces 347PS and delivers up to 700 Nm (516.3 lb-ft) of torque to the crankshaft, available between 2,500 and 3,100 rpm. This combination of power, torque and efficiency sets the S5 apart in this segment.
The 3.0 TDI in the S5 models is the most powerful version in the Audi V6 diesel engine line-up. Both the electric powered compressor (EPC) and mild hybrid (MHEV) systems are embedded in the standard 48-volt main electrical circuit. For the first time in the S5 TDI, a powerful 48–volt belt alternator starter is the heart of the mild hybrid system with maximum recuperation power of up to 8 kW. A DC/DC converter steps this voltage down for components in the 12–volt electrical system. A compact, air-cooled lithium-ion battery with a capacity of 0.5 kWh installed under the luggage compartment floor serves as the energy centre.
With these characteristics, the V6 diesel engine is the ideal power plant for agility, spontaneity, low fuel consumption and long range, with a suitably resonant sound to match.
Acceleration to 100kmh in the S5 Coupé takes 4.8 seconds and and 4.9 seconds in the S5 Sportback, with both reaching their peak at an electronically limited 250kmh.
The EPC: fast support for the turbocharger
The electric powered compressor in the Audi S5 TDI is new to this segment. It is located in a bypass downstream of the intercooler and thus close to the engine. From the outside, the compressor looks similar to a conventional turbocharger. A compact electric motor replaces the turbine wheel, however. With an output of up to 7 kW, it accelerates the compressor wheel to 65,000 rpm in approximately 300 milliseconds. It is activated whenever the power demand from the driver is high but the energy available in the exhaust flow for driving the compressor wheel is low. If this is the case, the bypass valve closes and directs the intake air to the EPC. The compressed air flows directly into the combustion chamber. This enables the driver to tap the full power of the 3.0 TDI instantly even at low engine speeds, whether passing another vehicle or accelerating out of a corner. Because the technology increases torque at the lower end of the rpm range, it provides for lower engine speeds and less frequent downshifts during relaxed driving. From a standing start, the new S models quickly move several metres ahead of comparable vehicles without an EPC.
MHEV technology: recuperate or coast
The mild hybrid system in the S models, which is also integrated into the new 48-volt electrical system, has the potential to reduce customer fuel consumption by as much as 0.4 litres per 100 kilometres. Mounted on the end face of the 3.0 TDI is a water-cooled belt alternator starter (BAS), which is connected to the crankshaft via a particularly high-load poly-V belt. The BAS generates a recuperation power of up to 8 kW and 60 Nm (44.3 lb-ft) of torque.
It interacts closely with the TDI engine, which in many situations can be operated more closely to its ideal load point as a result. That enhances efficiency.
The engine management system decides in every situation whether coasting, freewheeling or recuperation, i.e. the recovery of kinetic energy, is most efficient. It does this using information from the navigation system and the onboard sensors. The energy recovered by the BAS during coasting and braking flows into the 48-volt storage unit or directly to the electrical consumers.
The mild hybrid system not only reduces fuel consumption; it also provides greater comfort and convenience. The conventional starter is only used to start the car initially, when cold engine oil requires high forces. When the driver presses the accelerator pedal again after a coasting phase or a stop, the BAS restarts the combustion engine. The system does this as required by the driver’s wishes and the situation, from very smoothly to very quickly. Start-stop operation begins at 21kmh. When stopped, the engine restarts as soon as the car in front starts to move, even if the brake is depressed.
The engine: torquey and efficient
The 3.0 TDI is a high-tech engine. Its common rail system injects fuel at a pressure of up to 2,500 bar. Crankshaft, pistons, connecting rods and oil management have been designed for high performance, and sophisticated measures have been taken to reduce friction in the crankshaft and camshaft drive. The thermal management system features separate coolant loops for the crankcase and cylinder heads so that the engine oil heats up quickly following a cold start. The coolant flow is directed to the oil cooler, the EPC, the BAS and the compressor case of the turbocharger as needed.
The large turbocharger generates up to 3.4 bar of absolute charging pressure. Its variable turbine geometry (VTG) is optimised for low-loss flow. The external low-pressure exhaust gas recirculation (EGR) system extracts the exhaust gas downstream of the particulate filter. This enables the turbocharger to be operated with the full mass flow, significantly increasing its efficiency.
The eight-speed tiptronic: lightning-fast and smooth
The 3.0 TDI transmits its power to a lightning-fast and smooth-shifting eight-speed tiptronic. Its lower gears feature short, close ratios, while the upper gears are long to reduce revs and fuel consumption.
The driver can let the torque converter automatic transmission work on its own or actively control it, in which case the driver’s commands are transmitted electrically. The shift sequence and connection logic are optimized for the rapid development of traction. The transmission control system avoids unnecessary shifting in stop-and-go situations.
New detailed solutions improve the close interplay between the tiptronic and the mild hybrid system. A clutch in the central transmission interrupts the flow of power when the car is rolling and the engine is either idling or shut off. When coasting, an electric oil pump independent of the combustion engine makes it possible to engage the gear required at restart. Additional technology modules contribute to efficiency. Narrow springs at the multi-plate brakes in the gear sets separate the plates from one another and thus reduce drag torque. The torsion damper in the tiptronic’s converter includes an rpm-adaptive damper that largely attenuates the vibrations of the V6 diesel that occur at very low engine speeds.
quattro permanent all-wheel drive: self-locking centre differential
The quattro permanent all-wheel drive system transfers the engine power from the eight-speed tiptronic to the wheels. At the heart of the drivetrain in the Audi S5 Coupé TDI and S5 Sportback TDI is a self-locking centre differential. It normally distributes the torque in a ratio of 40:60 between the front and rear axle. If a wheel loses traction, the differential send the majority of the power to the axle with the better grip, with as much as 70 percent going to the front or up to 85 percent to the rear.
Wheel selective torque control – a software function of the ESC Electronic Stabilisation Control – perfects the handling. It brakes the two wheels with reduced load on the inside of a bend slightly before they can begin to spin.
The difference between propulsive forces at the wheels makes the car turn into the corner ever so slightly – making handling even more precise, agile and stable.
quattro with sport differential
The optional sport differential further optimises handling. During dynamic cornering, the sport differential literally pushes the car into the corner and eliminates any hint of understeer. When turning into or accelerating in a corner, most of the torque is distributed to the outside rear wheel. The sport differential ensures that steering commands are carried out precisely and stably, providing for outstanding agility. Integration into the Audi drive select dynamic handling system also allows the driver to choose between different sport differential setups.
Sport suspension, with the option of fast-acting damper control
The sophisticated suspension contributes to the dynamics of the S models. The front and rear axles are five-link constructions made largely of aluminium. Two subframes connect the links to the body. The track width is 1,587 mm at the front and 1,568 mm at the rear. The Coupé has a wheelbase of 2,765 mm; the Sportback 2,825 mm.
With a ratio of 15.9:1, steering is direct and features an S-specific power assist system. It filters out intrusive road inputs while passing useful information to the steering wheel. Audi also offers dynamic steering as on option. It uses a superposition gear to vary its ratio by up to 100 percent as a function of the car’s speed and the mode selected in the Audi drive select dynamic handling system. At the cornering limit, dynamic steering stabilises the car with lightning-fast steering inputs.
Audi offers the optional suspension with damper control, in which electromagnetic valves regulate the flow of oil in an energy-efficient manner: Higher power is only provided if the valves are closed to firm up the dampers. There is a wide range between a soft ride and firm handling.
The electronic chassis platform (ECP) controls the dampers in millisecond cycles. The high-tech control unit collects comprehensive information about the movement of the car and the data from the chassis control systems involved.
From these, it quickly calculates and precisely coordinates the optimal function of these components. Besides the controlled dampers, the ECP also controls the optional sport differential. The latter and the dynamic steering are integrated into the Audi drive select dynamic handing system, which also affects the throttle valve, tiptronic, power steering and other technology modules.
The driver can adjust their function by switching between the profiles comfort, auto, dynamic, efficiency and individual (only with MMI navigation system).
Discreet and elegant design
The wide, low Singleframe grille features three-dimensional aluminium struts and is flanked by the standard LED headlights. The front bumper is strongly three-dimensional and richly contoured. U-shaped clasps structure the large, pentagonal air inlets, which are partly filled with honeycomb grilles. Separate openings on their outer edge direct a portion of the airflow into the wheel housings, where it flows past the wheels for improved aerodynamics. A horizontal, aluminium-look blade in the bumper forms the lower edge of the nose.
When viewed from the side, the exterior mirrors with their aluminium-look housings and the strongly contoured side sills are particularly eye-catching. The S5 Coupé and the S5 Sportback have a spoiler integrated into the luggage compartment lid. LED rear lights with dynamic turn signals are standard. A flat honeycomb grille is integrated into the rear bumper, while a diffuser insert in titanium black matt frames the two dual chrome tailpipes of the exhaust system.
Inside, the seat coverings – optionally with contrast stitching – are available in either a leather/Alcantara combination or the top grade Fine Nappa leather. Buyers can choose from the colours black, rotor grey and magma red.
Sport seats with an embossed S logo are standard. Strongly contoured super sport seats with integrated head restraints, rhombus pattern and massage function are optionally available. The MMI display displays a welcome screen with an S5 logo when the ignition is switched on. Illuminated door sill strips, the sport leather steering wheel with multifunction plus and the clasp on the tiptronic selector lever bear the S logo with a red rhombus. The pedal caps and the footrest are stainless steel; the inlays are made of matt brushed aluminium or optionally carbon Atlas.
Controls and infotainment: well-connected and informed
The MMI system on board the S5 models offers a highly modern control logic. With its flat hierarchies, it is oriented on modern smartphones, including the intelligent free-text search function.
The voice control function recognises inputs from everyday speech. Audi virtual cockpit fitted as standard also presents all key information on its 12.3-inch display. One of the three views from which the driver can choose is the S mode, in which the tachometer takes centre stage. The optional head-up display projects important data onto the windscreen as symbols and digits.
The infotainment system for the S models is modular, with MMI navigation plus with MMI touch and an 8.3-inch monitor topping the infotainment range. The rotary pushbutton has a touchpad for zooming, scrolling and entering characters. The system includes the Audi connect hardware module, which connects the car to the internet via LTE and also includes a Wi-Fi hotspot. It also delivers the numerous Audi connect internet services to the car, ranging from traffic information online to remote functions. The free myAudi app connects a smartphone with the car.
The optional Audi phone box connects smartphones to the on-board antenna by near-field coupling and charges them inductively using the Qi standard. Particularly discerning hi-fi fans can choose the Bang & Olufsen Sound System with 3D sound. The Audi smartphone interface brings Apple CarPlay and Android Auto on board for iOS and Android phones, respectively.
Driver assistance systems: comfort and safety
The S5 Coupé TDI and S5 Sportback TDI make driving even more relaxed and comfortable with a wide range of driver assistance systems. Highlights include adaptive cruise control including traffic jam assist, collision avoidance assist, turn assist and rear cross traffic assist.
The Audi S5 models with TDI engines will be available in the UK from late 2019. Standard items of equipment include LED headlights with dynamic turn signals, tautly tuned S sport suspension and damping and power-adjustable front sport seats with Alcantara leather, embossed S logo and seat heating.