Last month, Audi divulged the facelifted versions of its A5 range, which include the Coupe, Convertible and Sportback models.

While the cosmetic changes were minor, the Ingolstadt-based company introduced a new 1.8-liter TFSI 4-cylinder engine that will power the entry-level A5 models. Now, Audi decided to share the full details of its new, more powerful and at the same time more frugal gasoline unit.

The new 1.8 TFSI has a displacement of 1,798 cc. It produces 170HP at a rather low 3,800 rpm and, more importantly, 320 Nm (236 lb/ft) of peak torque from 1,400 rpm until 3,700 rpm. When equipped with a manual-gearbox, the A5 Coupe 1.8 TFSI accelerates from 0-100 km (0-62 mph) in 7.9 seconds and reaches a top speed of 230 km/h (143 mph).

Audi says the four-cylinder engine is much more fuel efficient than its predecessor as average consumption has been reduced by 21% to just 5.7 lt/100 km (41.27 mpg), while CO2 emissions are the lowest in its class, with 134 g/km.

Naturally, the force-fed 1.8-liter unit meets the Euro 6 standards which will be implemented in 2015.

Audi has achieved this by paying particular attention to the combustion behavior of the engine. For example, the new unit features direct fuel injection (FSI) but with rail pressure increased from 150 to 200 bar. At the same time, it also uses indirect injection where fuel is sprayed at the end of the intake manifold when the engine operates at part-load. The direct injection system operates at start up and at higher engine loads. In addition, the variable valve system operates on the exhaust side and adjusts the camshafts in 2 angles, 30 or 60 degrees.

The new 1.8 TFSI is lighter by 3.5 kg (to 131.5 kg) than the previous unit and features an all-new turbocharger with a maximum boost pressure of 1.3 bar. The turbine wheel is manufactured by a new alloy that can withstands temperatures up to 980 degrees Celsius and the electronic boost pressure controller adjusts pressure immediately in order to reduce fuel consumption.

It also has a fully electronically regulated cooling system that aims to bring the oil to operating temperature as fast as possible. This is done by operating the main radiator only at the last possible moment and by keeping the coolant in the crankcase for a long time. The exhaust manifold is integrated into the water-cooled cylinder head, reducing exhaust gas temperature and thus doing away with the need to use a rich fuel mixture at full engine load, further reducing consumption.

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