The long-stroke 2.0 TFSI in the Audi S3 has been developed from scratch. The only thing it has in common with its predecessor, which was named Engine of the Year five times in a row between 2005 and 2009, is its displacement of 1,984 cc (bore x stroke 82.5 x 92.8 millimeters [3.25 x 3.65 in]). The four-cylinder unit delivers a constant 380 Nm (280.27 lb-ft) of torque to the crankshaft between 1,800 and 5,500 rpm. Rated power at 5,500 rpm is 221 kW (300 hp), and the engine redlines at 6,800 rpm.
The S3 delivers impressive performance. The sprint from zero to 100 km/h (62.14 mph) is completed in 4.8 seconds when equipped with the S tronic (5.2 seconds with the manual transmission). The electronically governed top speed of 250 km/h (155.34 mph) is just a formality. The S3 with S tronic consumes on average just 6.9 liters of fuel per 100 km (manual: 7.0 liters) [34.09 and 33.60 US mpg]. This corresponds to CO2 emissions 159 (162) grams per kilometer (255.89 and 260.17 g/mile) and for models equipped with the manual transmission, an improvement of 1.5 liters compared with the previous version.
The powerful four-cylinder engine features two balance shafts rotating at twice the speed of the crankshaft for tremendous smoothness. The sound is emotion-inspiring and sporty. An electromechanical sound actuator at the bulkhead brings the engine sound to life in the cabin. The exhaust system also includes a sound flap that opens at certain engine speed ranges to give the S3 a sportily sonorous sound.
The 2.0 TFSI boasts groundbreaking solutions in many fields of technology. One of these is the additional use of indirect injection. It supplements the FSI gasoline direct injection at part load to reduce consumption and particulate emissions. FSI injection, which works at pressures up to 200 bar, is used when starting and at higher loads.
The developers achieved new degrees of freedom when it comes to filling the combustion chambers. On the exhaust side, the Audi valvelift system varies the stroke of the valves in two stages; the camshaft on the intake side can be adjusted steplessly through 30 degrees of crankshaft angle while 60 degrees of adjustment is available on the exhaust side. The compression ratio of 9.3:1 is unusually high for a turbocharged engine.
The exhaust manifold is integrated into the cylinder head, where it is bathed in coolant. This solution lowers the temperature of the exhaust and accelerates warmup following a cold start, which lowers consumption during the cold-start phase. This concept also has a positive effect on fuel consumption during sporty driving because full-load enrichment is no longer necessary. The large turbocharger is also a new development. It achieves a maximum boost pressure of up to 1.2 bar for even more spontaneous engine response. A high-performance intercooler integrated into the water circuit greatly reduces the temperature of the compressed air and thus increases the amount of air required for combustion.
With the 2.0 TFSI’s innovative thermal management system, two rotary slide valves consolidated in a single module regulate the flow of coolant. These valves ensure that the engine oil heats up to its operating temperature soon after the vehicle is started; they also maintain the coolant temperature, as per a given driving situation, between 85 and 107 degrees Celsius (185.0° F and 224.6° F). As a result – regardless of load or engine speed – the valves always strike the perfect balance between minimal friction and high thermodynamic efficiency.
The 2.0 TFSI has been designed specifically for use in the new Audi S3. Pistons with stronger bolts and new rings plus reinforced connecting rods with new mounts transfer the power to the crankshaft. The gray cast iron crankcase has been reinforced at the main bearing seats and the main bearing cover.
The cylinder head is made of a new, particularly lightweight aluminum-silicon alloy characterized by high strength and temperature resistance.
An innovative coating on the piston skirts and mounting the balance shafts in roller bearings keep internal friction low. The regulated oil pump only consumes as much energy as is necessary for the current driving situation.
Despite its complexity and the high performance, the new 2.0 TFSI weighs just 148 kilograms (326.28 lb) – more than five kilograms (11.02 lb) less than the previous engine. The dimensions are compact: 603 millimeters (23.74 in) long, 678 millimeters (26.29 in) wide and 664 millimeters (26.14 in) high.
Transmissions
The new Audi S3 comes standard with a manual six-speed transmission with a lightweight magnesium case. The optional S tronic boasts high efficiency and a tall sixth gear. The lower gears are short in the interest of dynamics, as is also the case with the manual transmission.
The S tronic comprises two subunits, with two multi-plate clutches controlling the gears. The large K1 clutch located on the outside directs the torque via a solid shaft to the gear wheels for gears 1, 3 and 5. A hollow shaft rotates around the solid shaft. It is connected to the smaller K2 clutch, which is integrated inside its larger sibling, and which acts on the gear wheels for gears 2, 4 and 6, as well as reverse.
Both transmission structures are continuously active, but only one of them is connected to the engine at any one time. For example, when the driver accelerates in third gear, the fourth gear is already engaged in the second transmission section. Shifts are performed by switching the clutches. This takes just a few hundredths of a second and happens so quickly and smoothly that it is barely perceptible.
S tronic can be operated using the short selector lever or with the optional paddles on the steering wheel. It includes the modes D and S in addition to manual mode. The driver can activate launch control at the push of a button. This manages starts with controlled tire slip to deliver maximum engine power to the road.
quattro permanent all-wheel drive is an integral component of the powertrain. It gives the new top model in the A3 series a decisive edge over its two-wheel-drive competition. The Audi S3 can accelerate earlier and more safely when exiting a corner. It remains dynamic and stable under all conditions, particularly in the rain and snow.
The heart of the quattro drive system is an electronically controlled and hydraulically actuated multi-plate clutch. In the interest of balance axle load distribution, it is located at the end of the prop shaft, in front of the rear axle differential.
Inside is a package of plates that rotate in an oil bath. The metal friction rings are arranged behind one another in pairs – one ring of each pair is rigidly meshed with the housing, which rotates with the prop shaft; the other ring is meshed with the output shaft to the rear axle differential.
During normal driving, the clutch sends most of the engine’s power to the front wheels. If traction decreases there, the clutch can transfer torque steplessly to the rear axle in just a few milliseconds by forcing the packages of plates together via controlled action. An axial piston pump generates the necessary pressure almost instantaneously.
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