Friday 8 May 2015

‘Rightsizing’ gasoline 2-litre from Audi

The first production appearance of Audi’s new 2-litre gasoline engine will be in the A4 due later in 2015.
Audi claims its new 190PS 2-litre TFSI as the most efficient petrol-powered unit in its class.

Over 10 years ago, Audi launched its first series production engine featuring a ground-breaking combination of turbocharging and direct injection. This made the brand the trendsetter in down-sizing and down-speeding.

Professor Dr. Ulrich Hackenberg, member of the board of management for technical development at Audi, says the reduction in displacement and engine speed can be optimally effective only if reasonably related to the vehicle class and the customers' everyday use. 

"Rightsizing thus involves the optimal interplay of vehicle class, displacement, output, torque and efficiency characteristics under everyday conditions."

The four-cylinder engine delivers 190PS and 320 Nm (236 lbft) torque from a displacement of 1,984 cc. The high torque is applied in a wide speed range from 1,450 to 4,400 rev/min.

Audi also claims a ground-breaking maximum fuel economy in excess of 56 mile/gal according to the NEDC cycle.

To achieve this, Audi claims the engine has a new combustion method. At its core its principle is comparable to the Miller cycle. The increase in efficiency is based on the following factors:

The intake time has been significantly shortened (140° crank angle (CA) rather than 190 to 200° CA).

Owing to a higher boost pressure on the inlet side, the engine attains optimal cylinder charges despite the shorter intake time.

The intake valve also closes earlier -well before the bottom dead centre is reached. This lowers the medium pressure, allowing a high, efficiency-boosting compression ratio.

In the partial load range, an additional injection upstream from the intake valve yields an efficient mixture formation that is already complemented by the direct injection in the intake manifold and in the combustion chamber.

The Audi Valvelift System (AVS) on the inlet side allows a short intake time at partial load and a longer time at higher loads (full load: 170° CA).

Beyond the new combustion method, the new engine weighs in at a relatively modest 140 kg, avails itself of other efficiency technologies. For example, the coolant flow is controlled so as to greatly shorten the engine warm-up time. The integration of the exhaust manifold into the cylinder head also brings benefits, as does the use of low-friction engine oil (0W-20).

The package of high-tech solutions makes the new 2-litre TFSI a high-efficiency engine that “sets a new benchmark in its segment”. Audi will introduce the new generation of engines in the new Audi A4, and then in other model series.

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