The Audi A1 drive TrAin Turbocharged engines and dual-cluTch gearbox The turbocharged engines emphasise the Audi A1’s sporty market positioning. The spark-ignition engines with

gasoline direct injection and the common-rail diesels all have ample pulling power and dynamism, allied to low

fuel consumption and compliance with the EU5 exhaust emission limits. The seven-speed dual-clutch gearbox

is available for A1 versions with gasoline or diesel engine.

Audi A1 DrivE TrAin

The 1.2-liTre, 63 kW TFSi engine

The TFSI engine with a displacement of 1.2 litres is the entry-level direct-injection, turbocharged unit. It continues the TFSI success story in a smaller engine-size category. This friction-optimised engine, ❶, with an improved combustion process, helps to reduce the car’s fuel consumption. The principal development goals were reducing mechanical losses and optimising the weight of the complete engine.

A major factor in weight reduction is the aluminium engine block, which has grey cast iron cylinder liners. By reducing the diameter of the big-end and main bearings to 42 mm, further optimisation of the weight of the steel crankshaft became pos-sible. Overall efficiency improvements were obtained by a pis-ton ring set with reduced tangential tension and by lowering the volumetric flow of engine oil, using a gallery pressure con-trolled oil pump. Two valves per cylinder and reduced main and big-end bearing dimensions have cut friction and the amount of oil needed for lubrication. Flow restrictions have been elimin-ated from the dual coolant circuits, ensuring that the ideal oper-ating temperature is reached quickly. The electrically controlled waste gate for the integral turbocharger, which has also been optimised, responds more rapidly and with greater precision. In conjunction with a coolant-filled charge air intercooler mounted directly in the intake manifold, the turbocharger helps the engine to develop its full torque of 160 Nm from an engine speed of 1500 rpm upwards, ❷. This torque is transmitted to the wheels on entry-level versions of the A1 by a five-speed manual gearbox. The engine complies with the EU5 exhaust emission limits and is equipped as standard with a start-stop system; it is therefore well equipped to satisfy future needs. ❸ is a summary of the engine’s key technical data.

The 1.4-liTre, 90 kW TFSi engine

The A1 introduces a further TFSI engine to the subcompact segment. The compact 1.4 TFSI engine, ❹, with a power out-put of 90 kW and a maximum torque of 200 Nm available between 1500 and 4000 rpm, confirms the A1’s sporty posi-tioning, ❺. Moderate downsizing and the availability of this direct gasoline-injection engine’s full torque even at low engine speeds avoids any hint of weakness when starting from a standstill. The coolant-filled charge-air intercooler integrated into the intake manifold ensures a more direct re sponse on an engine with four valves per cylinder as well. Maximum power output is obtained at 5000 rpm; higher engine speeds are not needed to utilise the engine’s performance potential. These characteristics enable the engine to be run at extremely low speeds and the fuel consumption distinctly reduced. In the A1 it is available with a six-speed manual gearbox or with the seven-speed S tronic dual-clutch gearbox. Both drive trains feature a start-stop system and recuperation system as stand-ard equipment: measures that help this efficient engine to consume even less fuel. ❻ is a summary of the engine’s key technical data.

dAniel herrmAnn is Project Manager in Power Unit

Development at AUDi AG in ingolstadt (Germany).

AUTHor

27June 2010 Audi A1

The 1.6-liTre Tdi dieSel engine

The 1.6-liter diesel unit powers a fur - ther highly efficient version of the Audi A1, ❼. This engine is available in two power categories. The 77 kW version can be obtained as soon as sales of the car begin. With the manual gearbox, it develops a torque of 250 Nm between 1500 and 2500 rpm, and makes the car fun to drive and economical at the same time, ❽. Even lower fuel consumption can be expected from the 66 kW en - gine, which has a maximum torque of 230 Nm. In conjunction with the five-speed gearbox, its CO2 emissions are only 99 g/km. Both engines are equipped with the start-stop system and recuperation system as standard features.

Common-rail fuel injection together with the systematic application of other fuel-saving measures is the key to this diesel engine’s success. Development work has significantly reduced its friction losses. The fuel injection system, a new development, operates at an injection pressure of 1600 bar, and thanks to piezo injectors with controlled multiple injec-tion (up to six injections for each com-bustion stroke) the pressure gradient is less steep, and the engine’s acoustics benefit. The necessary amount of fuel is supplied by a twin-piston high-pressure pump, which is combined with an inte-gral fuel pre-delivery pump on the higher-output engine. On the 66 kW engine the mechanical fuel pump is replaced by an electric unit in the fuel tank. Friction losses have been reduced even further by piston rings that exert less tangential force and by a volumetric flow-controlled oil pump driven by a toothed belt running in an oilbath. The cast aluminium pistons have a shallow bowl for uniform heat distribution and are attached to the conrod by a DLC (dia-mond-like carbon) coated gudgeon pin, which reduces friction still further. A special honing pro cess increases the dimensional accuracy of the cylinder liners and helps to keep engine oil con-sumption low. The width of the toothed belt has been changed and belt tension lowered, again in order to minimise fric-tion losses and cut fuel consumption. A large number of similar measures have been taken to continuously improve the

❷ Power output and torque diagram for the 1.2-litre gasoline engine

❸ Technical data of the 1.2-litre gasoline engine

❶ The 1.2-litre TFSi gasoline engine

Audi A1 DrivE TrAin

28

❻ Technical data of the 1.4-litre gasoline engine

Communicating in interna tional business

www.viewegteubner.de

technik bewegt.

❹ The 1.4-litre TFSi gasoline engine

❺ Power output and torque diagram for the 1.4-litre gasoline engine

29June 2010 Audi A1

engine’s overall level of efficiency. A tur-bocharger with variable turbine geom-etry (VTG) and other modifications to the air intake system round off this com-plete concept. Special engine software with a specific A1 application meters the injected fuel volumes precisely over the engine’s entire operating life. The car’s performance benefits from the engine’s abundant torque and power, but fuel consumption remains low. ❾ is a sum-mary of the key technical data for the engines in both power-output categories.

The S Tronic duAl-cluTch geArbox

The S tronic dual-clutch gearbox, ❿, combines the advantages of a manual gearbox with the convenience of an automatic trans mission. This explains why it is being adopt ed by Audi in more and more car categories. The strategy is continued in the Audi A1, where a seven-speed dual-clutch gearbox can be obtained with either a gasoline or a die-sel engine. The design of the gearbox supports the engine start-stop function. On the A1 with an output of 90 kW this facility is utilised for the start-stop sys-tem that is a standard feature. The two dry-plate clutches have further improv ed the efficiency of the gearbox. Each of them engages four gears. The first clutch on input shaft 1 is used to select first, third, fifth and seventh gears, the second on shaft 2 selects second, fourth and sixth gears and reverse. This divided action ensures that the next gear can be pre-engaged before the actual gear change takes place. The gearbox can therefore react more rapidly when the driver wishes to accelerate. When a gear change takes place, the power flow from the engine is transferred from one clutch to the other with no interruption. Since the clutches are engaged actively, the gear change pro cess is extremely sensi-tive and smooth. Oil for gearbox control is taken from a pres sure reservoir sup-plied by an electric demand-controlled pump. Since the design of the S tronic dual-clutch gearbox is closely based on a conventional manual gearbox, it has a comparable high level of efficiency. This is the key to the very low fuel consump-tion recorded by the Audi A1 with S tronic. The driver can influence the car’s response in three ways: in the “D” ❾ Technical data of the 1.6-litre diesel engines

❽ Power output and torque diagram for the 1.6-litre diesel engines

❼ The 1.6-litre TDi diesel engine

Audi A1 DrivE TrAin

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mode, the gear change program is rated for maximum refinement and high effi-ciency. The engine tends to remain in the lower engine speed range, but higher speeds are available im mediately if the kick-down function is op er ated. For the sporty-minded driver who wishes to have the engine’s power on tap with no delay, the “S” mode is the correct choice. The gear change program then selects lower gears at the same level of vehicle speed and allows the engine to run freely up to higher speeds. Individ-ual gears can be selected at the lever or the shift paddles on the steering wheel.

❿ The S tronic seven-speed dual-clutch gearbox

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31June 2010 Audi A1