Three re-designed engines will initially be available for the Audi A3 Sedan: one TDI and two TFSI units. Their engine displacements range from 1.4 to 2.0 liters, with power output between 103 kW (140 hp) and 132 kW (180 hp). Audi resolutely sticks to its downsizing commitment, as usual. Substituting engine displacement with turbocharging boosts performance and fuel efficiency alike.
In this context, technologies from Audi’s modular efficiency platform play a key role. The start-stop system, for example, relies on a high-performance Absorption Glass Mat (AGM) battery to reduce fuel consumption by 0.3 liters per 100 km. The innovative thermal management system ensures that the engine comes up to its operating temperature rapidly after a cold start – this shortens the phase of elevated friction losses due to viscous oil, and the car’s interior warms up faster as well.
All three engine versions are installed as per the same configuration: tilted backward by 12 degrees with the intake side at the front. This advancement from the Volkswagen Group’s modular transverse platform paired with the engine’s compact layout made it possible to position the Audi A3 Sedan’s front axle very far forward. This, in turn, has improved crash safety, the vehicle’s design and the distribution of axle loads (59% of power to the front and 41% to the rear).
Audi’s dedication to ultra-lightweight construction also extends to its engines. The re-designed 1.4 TFSI weighs a mere 107 kg (235.89 lb). And the 1.8 TFSI barely weighs 140 kilograms (308.65 lb) – thanks in part to a thin-walled crankcase that weighs 2.4 kg (5.29 lb) less than its predecessor. And, in the 2.0 TDI, relocating both balance shafts to the cylinder block saved 3.0 kg (6.61 lb).
Audi A3 Sedan: Initial engines
103 kW (140 hp)
250 Nm (184.39 lb-ft)
132 kW (180 hp)
250 Nm (184.39 lb-ft)
110 kW (150 hp)
320 Nm (236.02 lb-ft)
0 – 100 km/h (62.14 mph)
217 km/h (134.84 mph)
4.7 l/100 km (50.05 US mpg)
235 km/h (146.02 mph)
5.6 l/100 km (42.00 US mpg)
220 km/h (136.70 mph)
4.1 l/100 km (57.37 US mpg)
Vigorous power: The 2.0 TDI
The 2.0 TDI has been overhauled. Its 110 kW (150 hp) of power output is paired with 320 Nm (236.02 lb-ft) of torque between 1,750 and 3,000 rpm. The 2.0 TDI furthermore propels the Audi A3 Sedan from 0 to 100 km/h (62.14 mph) in 8.7 seconds en route to a top speed of 220 km/h (136.70 mph). Its average fuel consumption is a mere 4.1 liters per 100 km (57.37 US mpg) and it emits 107 grams of CO2 per kilometer (172.20 g/mile).
A reduction in friction was prioritized during development of this two-liter diesel engine, which features a displacement of 1,968 cm3 (bore x stroke 81.0 x 95.5 millimeters [3.19 x 3.76 in]). The toothed belts for the camshafts and ancillary components run smoothly and quietly. The balance shafts, relocated from the oil pan to the crankcase, boast anti-friction bearings and are lubricated by an oil mist. Elaborate needle bearings are used for the drive wheels of the camshafts, as well. The shafts are pressed into a separate bearing frame; a new valve train module exhibits high rigidity and low weight.
At the pistons, reduced stress on the rings results in smooth running. In manufacturing the engine, a honing process in fine machining of the cylinder liners guarantees high precision. The oil pump, with its two-stage control, requires very little drive energy. The cylinder block and the cylinder head have discrete coolant circuits supplied by dedicated pumps. During the engine’s initial warm-up period, only the cylinder head’s circuit operates.
The common-rail injection system in the 2.0 TDI generates up to 1,800 bar of pressure; eight-hole injection nozzles nebulize the fuel. A turbocharger with adjustable vanes is operated pneumatically. An intercooler is integrated in the intake manifold, facilitating short gas-travel paths, good control quality and high efficiency ratios. A new low-pressure, exhaust-gas recirculation system which is located near the engine is also very compact and designed to minimize friction losses.
With cylinder on demand: The 1.4 TFSI
In 2004, Audi became the world’s first manufacturer to pair direct gasoline injection with turbocharging – and the abbreviation TFSI has stood for great output, terrific torque and low fuel consumption ever since. A shining example of all these attributes, the 1.4 liter version has been overhauled. Its 103 kW (140 hp) of power output is paired with 250 Nm (184.39 lb-ft) of torque between 1,500 and 3,500 rpm. The 1.4 TFSI furthermore propels the Audi A3 Sedan from 0 to 100 km/h (62.14 mph) in 8.4 seconds en route to a top speed of 217 km/h (134.84 mph). It averages 4.7 liters per 100 km (50.05 US mpg), corresponding to 109 grams CO2 per km (175.42 g/mile).
Regarding the ultra-lightweight character of the 1.4 TFSI engine – which features a displacement of 1,395 cm3 (bore x stroke 74.50 x 80.00 millimeters [2.93 x 3.15 in]) – the single largest role is played by the crankcase. Unlike its predecessor made of cast gray iron, this die-cast aluminum innovation weighs a mere 18 kg (39.68 lb) instead of 33 kg (72.75 lb). Additional improvements made to the crankshaft, connecting rods and elsewhere have reduced the overall weight of the engine to 107 kg (235.89 lb).
Frictional losses have been reduced by as much as 20 percent compared with the previous engine. Improvements concern the piston rings, their reduced diameter at the crankshaft main bearings, lighter valves and toothed belts for the timing and ancillary drives designed to last the life of the engine. The pressure-controlled oil pump also contributes to engine efficiency. Like the 2.0 TDI, the 1.4 TFSI has a valve train module with low-friction camshaft bearings, whereby these shafts are integrated directly in the cylinder-head cover. The intake camshaft can be adjusted by 50 degrees of crank angle.
Intelligent thermal management: The exhaust manifold
Another innovation is integration of the exhaust manifold in the cylinder head. It quickly brings the coolant to operating temperature after a cold start; only then does a thermostat in the new coolant pump module enable cooling of the crankcase. At full load – e.g. during very fast freeway driving – the cooling jacket reduces the temperature of the exhaust gases. This eliminates the process of enriching the fuel-air mixture which would otherwise be necessary – which improves fuel economy significantly.
The aluminum pistons have also been redesigned. The nearly flat design of the piston heads is precisely tuned to the intake ports, which have likewise been redesigned. The five-port nozzles of the common rail unit facilitate up to three injections per power stroke. The turbocharger has shed 1.8 kg (3.97 lb) compared to the previous engine. Its new electric wastegate adjuster is very quick and precise, which significantly improves engine responsiveness. An intercooler integrated within the intake manifold accelerates generation of boost pressure.
A particularly intriguing innovation in the 1.4 TFSI is the cylinder on demand (COD) system. A similar version is found in Audi’s large S and RS models. An advancement of the Audi valvelift system that varies valve stroke, it shuts down the second and third cylinders of the four-cylinder engine at low and moderate engine load during coasting. The system operates between 1,400 and 4,000 rpm and torques up to 100 Nm (73.76 lb-ft). Switchover lasts 13 to 36 milliseconds, depending on engine speed. This transition is accompanied by tweaks to fuel injection, ignition point and the throttle valve.
Valves are adjusted by sleeves, each of which has two different cam profiles. When these sleeves are axially adjusted on the camshafts by electromagnetically telescoping pins, something known as zero-stroke cam profiles rotate over the exhaust and intake valves. They do not actuate the valves, and the valve springs remain closed; at the same time, fuel injection is deactivated. In the active cylinders 1 and 4, on the other hand, efficiency rises, because their operating points are shifted to higher loads. As soon as the driver presses firmly down on the gas pedal, the cam units retract and the idle cylinders are reactivated.
Even with a 360-degree firing interval, the remarkably harmonized 1.4 TFSI runs very quietly and with little vibration, on account of modifications to the engine mounts, dual-mass flywheel and exhaust system. Fuel consumption as per standards of the ECE (Economic Commission for Europe) is reduced by some 0.4 liters per 100 km thanks to the COD system. Moderate driving can result in fuels savings as high as 20 percent.
High-tech engine: The 1.8 TFSI
The 1.8 TFSI showcases Audi’s high-tech expertise via numerous innovations. Of the engines initially available for the A3 Sedan, this is the most powerful. Its maximum torque of 250 Nm (184.39 lb-ft.) remains constant between 1,250 and 5,000 rpm. Power output amounts to 132 kW (180 hp). This four-cylinder engine also offers sporty performance, needing just 7.3 seconds to propel the A3 Sedan to 100 km/h (62.14 mph) before topping out at 235 km/h (146.02 mph). Its average fuel consumption is just 5.6 liters per 100 km (42.00 US mpg), which corresponds to 129 grams of CO2/km (207.61 g/mile).
One of the key innovations in the 1.8 TFSI is the addition of indirect fuel injection. During partial-load operation, it aids FSI direct gasoline injection. This system supplies fuel at the tip of the intake manifold to the tumble flaps, whereupon the fuel is intensively swirled with air. This enhances carburation, consequently reducing fuel consumption and particulate emissions. Direct fuel injection, which generates pressure as high as 200 bar, operates upon starting and at relatively high loads.
The turbocharger generates boost pressure very rapidly. Its notable features include an electric wastegate adjuster and a turbine wheel made of a new alloy that can withstand exhaust-gas temperatures nearly as high as 1,000 degrees Celsius (1,832 °F). Audi engineers have pushed the envelope by optimizing charging efficiency in the combustion chambers. The intake camshafts and exhaust camshafts are adjustable. The Audi valvelift system switches, as needed, between two settings regarding lift of the exhaust valves. Scavenging losses drop as a result. As in the 1.4 TFSI, the 1.8 TFSI’s exhaust manifold is integrated within the cylinder head.
Two rotary slide valves – housed in a single module and driven by a motor – regulate the thermal-management system of the 1.8 TFSI. They not only ensure that the engine oil is rapidly heated, but also maintain a coolant temperature between 85 and 107 degrees Celsius (185.00–224.60 °F) as per given operating conditions. Regardless of operating point, they strike an ideal balance between minimal friction and excellent efficiency.
Despite these new technologies, the 1.8 TFSI barely weighs 140 kilograms (308.65 lb). This is due in part to a crankcase made of cast gray iron; its walls are just three millimeters thick. The pistons consist of a new high-strength alloy. The oil pan is lightweight plastic and many bolts are aluminum. Internal friction is low thanks to a novel coating for the piston skirts, low-friction bearings for the two balance shafts and a narrower main bearing for the compact crankshaft. A regulated oil pump requires little energy itself and an electric system cools the piston heads with jets of oil.
Economical and strong: The other A3 engines
At some point in the not-too-distant future, Audi will offer the highly efficient 1.6 TDI for the A3 Sedan. This compact diesel engine delivers 77 kW (105 hp) of power from a displacement of 1,598 cm3 (bore x stroke 79.5 x 80.5 millimeters [3.13 x 3.17 in]). It also supplies 250 Nm (184.39 lb-ft) of torque, which remains constant from 1,500 to 2,750 rpm. It will emit less than 100 grams of CO2 per km (160.93 g/mile).
A particular strength of the 1.6 TDI lies in the ongoing minimization of internal friction. Key enhancements concern the oil pump, the piston rings, the honing process for the cylinder barrels, the toothed belt and the carbon-coated pins of the cast-aluminum pistons. The common-rail system’s piezo injectors facilitate as many as six injections per power stroke.
A tangential port in the intake manifold precisely whirls incoming air while an adjustable flap in the adjacent swirl port meters the fuel-air mixture as per load and engine speed. When the swirl port closes, the tangential port alone handles intake. A turbocharger with variable turbine geometry rounds out this engine.
Another engine, which is planned for the phase following the market launch, is the 2.0 TDI with 135 kW (184 hp) of power output and 380 Nm (280.27 lb-ft) of torque between 1,750 and 2,500 rpm. A third configuration of the two-liter diesel engine will offer 110 kW (150 hp) and comply with the emission limits of the EU’s Euro 6 standard. The single-most important technology module in these engines will be a unit that adjusts the camshafts by 50 degrees of crank angle. This unit, known as a valve star, is offset by 90 degrees. Each of the two camshafts actuates one intake valve and one exhaust valve per cylinder. A sophisticated emission-control system and an injection system generating as much as 2,000 bar complement this engine.
Among the gasoline engines, a 1.4 TFSI with 90 kW (125 hp) will be the entry-level unit.
The equipment and data specified in this document refer to the model range offered in Germany. Subject to change without notice; errors and omissions excepted.