Audi Q7 4.2 TDI in Depth

Press Release

Drivetrain

A sprint from zero to 100 km/h in 6.4 seconds and on to a top speed of 236 km/h – these figures illustrate the power of the Audi Q7 4.2 TDI, which is akin to that of a sports car. Its 90° V8 TDI draws on plentiful resources. The world’s mightiest diesel model in the SUV segment has superior pulling power on tap – at every speed and in every driving situation. The V8 transforms the Audi Q7 into a dynamic touring SUV with its serene and ultra-smooth operation, making long journeys a relaxed and supreme driving experience. On average, one full tank holding 100 litres is sufficient to cover 900 kilometres. The diesel, fitted as standard with a diesel particulate filter in compliance with the Euro 4 emissions standard, gets by on 11.1 litres per 100 km overall. The undersquare eight-cylinder TDI belongs to the new ultramodern V-engine family and is produced at the Györ plant in Hungary. With a bore of 83.0 mm and a stroke of 95.5 mm it has a displacement of 4,134 cc. It unleashes 240 kW (326 bhp) and a formidable 760 Nm of torque, which is available constantly between 1,800 and 2,500 rpm. The angle between cylinder banks on the range-topping TDI unit, which also powers the A8 luxury saloon, is 90 degrees, the spacing between cylinders 90 millimetres and its length a mere 520 millimetres. The crankcase is made of the high-tech material vermicular graphite cast iron, which is more rigid and more resistant to fatigue than grey cast iron. The graphite flakes produced during the casting process ensure that the microstructure elements are firmly interlocked. The relatively light crankcase forms the basis for the low weight of the engine – 257 kilograms – which enables a finely balanced distribution of mass between the front and rear axle. The crankshaft is forged from chrome-molybdenum steel; the pistons are made of cast aluminium. High-precision treatment of the bore surfaces using UV laser exposure reduces oil consumption to a minimum. The mighty TDI unit, housed beneath an elegantly styled bonnet, features a maintenance-free chain drive at the rear for its four camshafts and ancillaries. In the cylinder head, made of cast aluminium, low-friction roller cam followers actuate the 32 valves. Electronically controlled flaps in the intake tract set the intake air into a controlled swirl as required. At lower engine loads a high degree of swirl optimises combustion; at higher loads less swirl enables the combustion chambers to be filled to a high level. Both turbochargers – one for each cylinder bank – operate using electrically adjustable turbine geometry. Even at low engine speeds they provide solid torque and generate a relative boost pressure of up to 1.5 bar. Two large intercoolers lower the temperature of the compressed air, ensuring that the cylinders are filled more efficiently. The state-of-the-art common rail injection system features small, light piezo inline injectors, which respond extremely fast and with great precision by means of their electrically excitable piezo crystals. They can achieve up to five injection phases per power stroke. As a result, in conjunction with the robust engine construction and the particularly quiet valve gear, they make a vital contribution to the refinement of the high-tech diesel unit. Maximum injection pressure is 1,600 bar – this corresponds to the weight of a mid-size saloon on the area of a fingernail. The high pressure induces exceptionally fine atomisation of the fuel when it leaves the eight-hole nozzles. This ensures optimum mixture preparation and combustion and consequently high efficiency and low emissions.

Power transmission

The Audi Q7 4.2 TDI leaves the assembly line equipped as standard with the highly efficient tiptronic automatic transmission. Its six wide-spaced gears fully exploit the mighty pulling power of the diesel engine. Off-road, the torque converter with its damping action and torque multiplication is particularly useful when driving off and when driving slowly on inclines. A reduction gear is superfluous. The gear shifts are precise, spontaneous and harmonious in every situation. The tiptronic was designed from the very outset for high torque and is extremely well matched to the V8 diesel powerplant. Management of the tiptronic is taken care of by the dynamic shift program DSP, which orients itself to the individual style of the driver and to the prevailing road conditions. In the special sports program – S mode – the computer performs gear shifts later and faster when accelerating. The driver can take command at any time, either via the special shift gate on the selector lever or via optional paddles on the steering wheel. These manual shifts are particularly sporty. The Audi Q7 series employs the latest generation of the quattro permanent four-wheel drive. The self-locking centre differential – a purely mechanical planetary gear – provides fast asymmetric/dynamic torque distribution according to available traction at the front and rear axle: under normal driving conditions the front axle is assigned 40 per cent of the propulsive force, the rear axle 60 per cent. If required, the differential can deliver up to 65 per cent to the front or up to 85 per cent to the rear. If a wheel at one axle starts to spin, the electronic differential lock EDL controls distribution between left and right by means of brake intervention. The quattro drive in the Audi Q7 4.2 TDI provides optimum grip, safety and driving enjoyment in every situation. Its sporty basic setting produces exceptional agility that sets the benchmark – and not just in the SUV segment.