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Audi A5 Sportback to debut fuel-sipping 1.8

A5 hatched: A5 Sportback will be the first model powered by Audi's new 1.8 TFSI.

Breakthrough petrol engine from Audi gets diesel-like torque and efficiency

8 Aug 2011

AUDI’S new super-efficient 1.8-litre turbo petrol engine will make its Australian debut in the mid-range A5 Sportback in the first half of 2012 before spreading to other models in the range.

The four-cylinder 1.8 TFSI – generating as much torque as Audi’s existing 2.0-litre turbo engine while slashing fuel consumption by more than 20 per cent over the existing 1.8-litre turbo in the A4 and A3 – will provide a new gateway to the A5 Sportback range, which currently starts with the $68,900 2.0 TSFI.

Prices and other details of the new A5 Sportback variant will be released closer to the launch date, but Audi Australia has indicated that the 1.8 TSFI will be an additional model, not a replacement for the 2.0 TSFI.

Audi Australia general manager corporate communications Anna Burgdorf said it was likely the new engine would appear in other models in future.

“Once a new engine comes, it is more than likely we will see it in other models, particularly an engine that is this efficient,” she said.

“Obviously that is an area of huge interest for us, to promote efficiency and better performance – it is a constant cycle we are looking at with our engine technologies.”

The new engine uses a range of new technologies to boost power from the existing 1.8-litre TFSI petrol engine’s 118kW to 125kW, while also lifting torque massively from 250Nm to 320NmThis peak torque – generated between 1400rpm and 3700rpm – is not only equal with the output of the bigger 2.0 TSFI petrol four but also that of the 2.0 TDI turbo-diesel widely used in Audi models.

7 center imageAudi claims a 0-100km/h sprint time for the A5 Sportback 1.8 TFSI of 7.9 seconds, which is more than half a second quicker than than the 132kW 2.0 TFSI A5 Sportback available in Australia in front-wheel-drive, but slower than the 6.6-second sprint time of the 155kW 2.0 TSFI quattro version.

However, the big news with the new 1.8 TFSI is fuel efficiency, slashing consumption from 7.2L/100km from the most efficient petrol A5 Sportback currently on offer, to 5.7L/100km.

CO2 emissions are said to be just 134 grams per kilometre – a 20 per cent improvement.

Audi says that places the new engine in the same league as some hybrids, although Toyota’s benchmark Prius returns 3.9L/100km and 89g/km.

It is certainly the most efficient petrol engine in its class, out-pointing the Mercedes-Benz 1.8-litre BlueEfficiency, which achieves 7.0L/100km in C-class form, and BMW’s 1.9-litre 320i, which returns 7.6L/100km.

The new Audi four-cylinder engine uses two forms of fuel injection to achieve its results – FSI direct injection and indirect injection.

Audi says indirect injection in the manifold is used in the part-load range to reduce both fuel consumption and particulate emissions, cutting them to such an extent that the four-cylinder engine already complies with the limits of the future Euro 6 standard that does not come into effect until 2015.

It says direct injection is activated at launch and at higher loads, performing two or three individual injection operations per work cycle.

As well, the valve-lift system, which adjusts the lift of the valves in two stages, has been upgraded to act on the exhaust valves as well as the intake valves. The two camshafts can be adjusted through 30 or 60 degrees of crankshaft angle.

To help the engine achieve operating temperature faster, the engine coolant is controlled by valves operated by an electronic module.

This isolates the engine coolant at cold start until the motor oil is hot, when it then opens the coolant to the radiator. The cabin heating runs off of a separate loop in the cylinder-head.

Audi says this thermal management system reduces the CO2 emissions of the 1.8 TFSI by around 2.5g/km.

Reduced exhaust gas temperatures made it was unnecessary for Audi to enrich the fuel mixture at full load, reducing fuel consumption “significantly” in sporty driving.

Audi has added a new turbocharger that develops up to 1.3 bar “systematically” through a range of improvements that include a new alloy turbine wheel that can withstand exhaust temperatures of up to 980 degrees Celsius.

Audi engineers have cut engine weight by 4.5kg with improvements to the turbocharger/cylinder-head module, a new casting process for the grey cast iron crankcase that reduces wall thickness to 3mm, a crankshaft with four rather than eight counterweights and reduced main bearing diameters.

As well, the pistons are made of new, high-strength alloy. Lightweight polymers are used for the oil pan, and many screws are made of aluminium.

Internal friction has been cut by a new piston skirt coating, while the balance shafts are now mounted on roller bearings.

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