Review of the new Audi A3 1.8 TFSI

The Audi A3 is a car with a lot to answer for. Responsible for popularising the premium hatch market sector, it was also instrumental in lending its Volkswagen Group paymasters to the notion that brands could be stretched in any specific direction. So it was that the company marketed Skodas that challenged Audis, Volkswagens that looked like Lamborghinis and sporty SEATs that were cheaper than Skodas. After all of this madness, the A3 suddenly seemed an eminently sensible idea, especially when presented with some of the more interesting engines at Audi's disposal. Engines like the 1.8-litre turbocharged FSI petrol powerplant.

Given pause to consider, the premium hatch has a tough job in justifying itself. All those layers of meticulously designed quality merely added to the weight of the car until such moment that it became too bloated to be enjoyable. Indeed, jump into many of the leading lights in this market sector - cars like the Mercedes C-Class Sport Coupe and the Alfa Romeo 147 - and it's easy to come away with the notion that keen drivers would prefer a humble Ford Focus. This illusion was cruelly exposed in the less powerful versions of the old A3 which had a tough time justifying their hefty asking prices, but power can be a wonderfully ameliorating thing and the sheer feel-good factor of cars like the S3 and the more powerful diesel versions made handing over a serious sum for a rather bijou hatch seem like a smart piece of business.

And to a certain extent it was. With residual values still jacked through the roof, nobody ever lost their shirt on an Audi A3. Of the current, facelifted range of cars, perhaps the most fascinating is the £18,500 1.8-litre TFSI-engined version, a model which had to answer four clear requirements. First and foremost it had to be enjoyable to drive, offering respectable performance and a willing feel. That was the easy part. Balancing such dynamism with fuel economy that reads more like that of a diesel car is a trickier call and when you factor-in drastic reductions in the amount of carbon dioxide and nitrogen oxides the car was permitted to churn out, the engineer's task became very tricky indeed. The answer was the Fuel Stratified Injection (or FSI) engine. At a stroke the old method of fuel being injected into an intake manifold appeared almost gratuitously profligate. Although it was kept quiet at the time, the 2001 Le Mans winning Audi R8 utilised such technology - the first time a gasoline direct injection car had claimed victory at La Sarthe.

"The 1.8TFSI engine manages the compromise between poke and economy very shrewdly"

So, how does FSI work? A high-pressure fuel line mounted on the side of the cylinder head, often dubbed the 'common rail', injects fuel straight into the combustion chamber. The shape of the pistons and the clever working of a set of valves make the air 'tumble', thus creating more efficient combustion. Where FSI engines really impress is their behaviour under part throttle loads. Whereas before, part throttle meant just that, partially strangulating the output by closing a butterfly valve the FSI system can be run with the throttles in a more efficient open position by creating a rich fuel mix directly next to the spark plug and a leaner mix in other parts of the combustion chamber. This is not only more efficient in terms of how much fuel enters the chamber in the first place but it also means that less energy is wasted as heat to the cylinder block. In effect a blanket of air shields the ignited fuel from the walls of the cylinder.

Part throttle is all well and good in day to day driving, but how does this benefit a Le Mans car? When the throttle is pressed wide open, the engine reverts to a more conventional 'homogenous' method of filling the combustion chamber with fuel and air. The 'tumble' effect and the synchronisation of air and fuel along with the careful metering of the high-pressure injection system all combine to offer more power and a cleaner engine. When you're dawdling you get great economy and when you want to drop the hammer you've got more power.

Clothe that engine in the latest A3 body and you should emerge with a class act. Longer, wider and lower than its predecessor, here is a car that punts the A3 back into pole position as the item of choice for the discerning young professional. The most obvious change is the increase in wheelbase. The styling is largely evolutionary, remaining obviously an A3 with the Audi trademark 'single frame' grille now featuring, only looking a little stretched. The additional 65mm in wheelbase has rectified one of the old A3's faults, namely that rear seat accommodation was a bit pinched. The extra 30mm of width also helps a little with shoulder room. If you need more room, there's a Sportback 5-door version with another 68mm of wheelbase in addition.

The latest, facelifted model has seen some changes to the car's styling. The front wings and the grille are a little shapelier, the headlights are sharper-looking and the side repeaters are now incorporated into the door mirrors

This 158bhp engine will prod the A3 1.8-litre TFSI through 60mph in 7.6 seconds and on to a top speed of 138mph, the acceleration helped by a quick-witted manual gearbox. The torque plateau ranges right from 1,500 to a heady 4,200rpm so you won't need to trouble the gearbox in the same way as you would a turbodiesel. A combined fuel economy figure that nudges 42.2mpg seems scarcely credible given the performance on offer. If you want more power, there's also a 197bhp turbocharged 2.0-litre TFSI on offer. Acceleration here is 0-60mph in 7.0s but fuel consumption slips to 39.2mpg.

The Audi A3 is a desirable package even when supplied with its most underwhelming engine but plug one of these 1.8-litre TFSI units up front and you gave a potent contender that loses little to the more expensive 2.0-litre TFSI, a powerplant which won the Engine of the Year award in 2005 and 2006. This smaller engine could even be the more cerebral purchase.

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