2010 Audi TTS

The Drivetrain

The TFSI engine fitted in the TTS summons its power from a displacement of 1984 cc, and blends two separate Audi technologies – gasoline direct injection and turbocharging – to form a partnership that is perfect for a sports car. It is with good reason that an international jury of motoring journalists has crowned the two-liter four-cylinder power unit "Engine of the Year" three times in succession since 2005.

It is not only the 265 of output that makes the TFSI so scintillating, there’s its hefty pulling power too – the maximum torque of 350 Nm (258.15 lb-ft) is constantly on tap from 2,500 up to 5,000 rpm. The Coupe with manual transmission takes just 5.4 seconds to race from zero to 100 km/h (62.14 mph), while a mere 4.4 seconds are required to speed up from 80 to 120 km/h (49.71 to 74.56 mph) in fourth gear. The Roadster is almost as impressive, recording times of 5.6 and 4.6 seconds respectively for the same two exercises. The electronic limiter calls a halt to this outstanding propulsion at a speed of 250 km/h (155.34 mph) in both models.

Compared to the engine it was derived from, the two-liter power unit has undergone extensive reengineering and strengthening to ready it for operation in the TTS – overhauled areas include the engine block, the cylinder head, the pistons, the connecting rods and the turbocharger, which can build up as much as 1.2 bar of relative air pressure. The intake and exhaust systems have undergone elaborate honing to allow the refined four-cylinder engine to both breathe freely and generate a powerful, resonant soundtrack. An optimized and highly efficient intercooler lowers the temperature of the compressed air, producing a crucial increase in the quantity of air supplied for combustion.

Thanks to its outstanding efficiency, the TFSI has impressive fuel consumption of 7.9 liters per 100 km (29.747 mpg) in the Coupe when partnered by the S tronic transmission, and just 8.0 l/100 km (29.375 mpg) in the Roadster. The two-liter engine is extremely light, weighing in at 153 kilograms (337.31 lbs). This has considerable benefits for the overall weight of the TTS as well as for the axle load distribution and, consequently, for the vehicle’s handling.

Strong basis: the 2.0 TFSI

The 2.0 TFSI in the Audi TTS incorporates key technical components of its 147 kW (200 hp) base engine. Its intake camshaft can be adjusted through 42 degrees for optimum cylinder charging and the two balancing shafts rotate at double the speed of the crankshaft to compensate for the second-degree inertial forces.

To equip it for use in the TTS, the undersquare engine was given a whole raft of radically reengineered features. The cylinder block has been reinforced at the main-bearing pedestals and the main-bearing cap. The piston pins, rings and connecting rods have also been adapted to the higher forces. The camshafts and annular valve seats, too, have been upgraded and the cylinder head consists of a new aluminum-silicon alloy.

The intake tract incorporates flaps that induce rolling movement in the incoming air. Special injectors inject the fuel into this “tumble” at pressures of up to 110 bar generated by a redesigned pump. The mixture has a lambda ratio of one – meaning one part fuel per 14.7 parts air. The compression ratio of 9.8:1 is in the same league as naturally aspirated engines, further enhancing the engine’s thermodynamic efficiency.

It operates with a larger turbine wheel so that the reengineered turbocharger can deliver a particularly large quantity of air. The turbocharger is an integral module made from thermally high-strength cast steel that also incorporates the exhaust manifold. It very rapidly achieves its maximum relative boost pressure of 1.2 bar. An intercooler lowers the temperature of the compressed air, increasing the engine’s thermodynamic efficiency as a result. The intercooler is made entirely from aluminum, making it even more efficient than a conventional component with plastic casing. The entire admission tract of the TTS has been optimized for minimum pressure loss. The development engineers successfully reduced the exhaust backpressure in the exhaust tract.

Audi’s powerful 2.0 TFSI engine weighs just 153 kilograms (337.30 lb), much less than the equivalent power unit of a key competitor. This benefits the overall weight of the TTS and is also a big advantage for its axle load distribution and thus handling. The engine measures just 652 millimeters (25.67 in) in length, 648 millimeters (25.51 in) in width and 666 millimeters (26.22 in) in height, making it ideal for transverse installation.

High-tech gearshifting: S tronic

Transmission of the engine’s power is handled as standard in the TTS by a manual six-speed gearshift with a light-weight magnesium housing. As an alternative, customers can opt for S tronic, which operates using six gears and two clutches positioned one behind the other. At high engine loads and rev speeds, it is capable of shifting in just two-tenths of a second. As a result of this high-speed shift work and its dynamic start-off capabilities, the dual-clutch transmission from Audi shaves a whole two-tenths off the time taken for the sprint from zero to 100 km/h (62.14 mph) in both the Coupe and the Roadster.

S tronic, which likewise boasts excellent efficiency, also allows the driver to shift gears manually using the one-touch lever or by means of paddles on the steering wheel, just like in a racing car. There is also a choice of two automatic operating modes: N for “Normal” and S for “Sport.” The clutches also have an adaptive design, enabling the start-off characteristics to be varied – whereas caution is exercised on slippery surfaces, full power can be unleashed at the driver’s command when there is firm grip.

The standard-specification quattro permanent all-wheel drive ensures loss-free transfer of the engine’s power to the road. With drive power being delivered to all four wheels, the TTS is able to accelerate quicker and more safely than its rivals, delivering dynamism coupled with supreme stability under all conditions. At the heart of the quattro system is an electronically controlled and hydraulically operated multi-plate clutch, which now works even faster than ever thanks to a new pressure reservoir. If required, all of the drive force can be redirected from the front to the rear wheels within a matter of milliseconds. To make allowance for the high torques produced by the TFSI engine in the TTS, the drive train has been reinforced as required.

Manual or automatic – the transmissions

A manual six-speed transmission is the standard solution for power transmission between the engine and wheels on the TTS. Both highly compact and ultra-light thanks to its magnesium casing, it perfectly reflects the characteristics of the top TT model. Its shafts and gears have been reinforced with an eye to the high engine torques, and gearshift travel is shorter. Gear changes are performed swiftly, with precision and ease – just as you would expect of an Audi.

Alternatively, the TTS is available with S tronic as an option – the dual-clutch transmission combines the strengths of an automatic with the benefits of a manual. It can change its six gears within just a few hundredths of a second without interrupting the power flow. S tronic responds with dynamic precision or serene poise depending on the requirements, making it the ideal partner for the TFSI engine. Its impressive efficiency is another factor that makes it ideal for the turbocharged four-cylinder engine.

The technical principle on which S tronic is based is as simple as it is brilliant: Two subsidiary transmissions, each with a multi-plate clutch, are integrated into a single casing. The first clutch serves the odd-numbered gears and reverse, and the second one serves the even-numbered gears.

The two input shafts share the same axle, with a solid shaft running inside a ollow shaft. Both subsidiary transmissions are continuously active, but only one is powered by the engine at any given time. If a gear is engaged by one of the subsidiary transmissions, the next is already preselected by the other; the gear change is accomplished by switching to the other clutch.

S tronic can be operated by the one-touch lever or – in motor racing style – via the shift paddles on the steering wheel. For added driver convenience, there are also two automatic operating modes: D (Drive) and S (Sport). S tronic’s clutches also have an adaptive feature and permit a variety of different starting characteristics. On slippery surfaces, they are engaged cautiously. When grip is good, the power is engaged forcefully if the driver so wishes.

Unbeatable: quattro drive

quattro permanent all-wheel drive, like S tronic, underscores the unique position of the TTS in the compact sports car segment. In both areas of technology, its competitors are unable to offer anything comparable.

The nerve center of the quattro drive system, developed specially for transversemounted engines, is a multi-plate clutch that is electronically controlled and hydraulically actuated.

The clutch is located at the end of the propshaft, in front of the rear axle differential – an installed position that improves the axle load distribution. Inside is a package of plates, running in an oil bath, which can be pressed together by
controlled hydraulic power. As this hydraulic pressure increases, the amount of torque diverted to the rear axle rises.

The clutch’s control unit permanently analyses the driving conditions using a wide range of data. If necessary, an electrically driven axial piston pump with five pistons nearly instantaneously generates the oil pressure needed by the clutches to divert the drive torque almost entirely from the front to the rear wheels. Thanks to a pressure reservoir, this process is completed twice as fast as it used to be – in a matter of milliseconds. All important stages of the drive line have been reinforced, from the propshaft through the differentials to the drive shafts.

Again in the TTS, the quattro principle delivers the supreme capabilities that have become an Audi hallmark – greater traction, slip-free acceleration, dynamic driving, safety and directional stability, together making up Audi’s proverbial Vorsprung durch Technik. The TTS handles dynamically and with supreme stability in all weather conditions.

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