A shimmering focal point on Audi’s exhibition stand: with its polished aluminium body, an A2 show car takes centre stage on Audi’s stand at the 2002 Geneva Motor Show. The explicitly metallic appearance of its outer panelling combines the visual lightness of the A2’s design with a clear indication that this product majors in the lightweight material aluminium.
There is more to the Geneva show car, however, than merely external qualities. It also demonstrates the pioneering technology that is about to be launched for the top-of-the-range A2 model version: a 1.6-litre petrol engine with FSI petrol direct injection, developing 81 kW (110 bhp) at 5800 rpm. The peak torque of 155 Newton-metres is available at 4500 rpm. The engine’s power is transmitted to the front wheels via a manual 5-speed gearbox.
Thanks to the low weight of the car’s aluminium body – 995 kg – the FSI engine propels this nimble athlete from 0 to 100 km/h in 9.8 seconds. The A2 1.6 FSI is capable of a top speed of 202 km/h, thanks in part to aerodynamic properties that are pioneering in the compact class.
The free-revving four-cylinder engine is impressive not simply for its sporting talents. The 1.6-litre FSI engine also demonstrates remarkable potential for fuel economy thanks to its petrol direct injection technology. The A2 1.6 FSI covers 100 kilometres on just 5.9 litres of Super Plus petrol (acc. to 1999/100/EC). Bearing in mind its performance figures and ample interior space, this is an unbeatably low value.
The new version broadens Audi’s range of A2 models to four. In addition to the two 1.4 versions with TDI and petrol engine, each of which develops 55 kW (75 bhp), the range includes a 1.2 TDI version, which became the first five-door, three-litre car when it was launched in 2001.
This version combines advanced technology, economy, ample space and driving fun to a quite unprecedented degree.
At the other end of the scale there is now the new 1.6 FSI which, in its own way, represents an equally exceptional synthesis. It is the top-performance version in this model line; with its agile running gear and precision steering, all the signs are that it will establish a new standard of dynamism and driving enjoyment. Yet when it comes to fuel consumption, the 1.6 FSI achieves values that are way below those for competitor models with similar performance and power output. It uses an average of only 5.9 litres of Super Plus per 100 kilometres (1999/100 EC).
Thanks to its larger tank, which now holds 42 litres of fuel, it is thus capable of a range of more than 700 kilometres. Together with its excellent performance figures, this gives the A2 1.6 FSI all the necessary credentials of a long-distance vehicle. Even at high average speeds, it will clock up a considerable distance on a single tank of petrol. And it will outstrip even nominally faster competitors as they pull onto the forecourt of the service station for a refill.
The A2 1.6 FSI is rather reminiscent of the Al2 study which Audi exhibited at the 1997 Frankfurt Motor Show: that vehicle already incorporated essential features of the revolutionary aerodynamics and space concept for which the A2 production models ultimately became renowned; as well as its ASF body, it had pioneering engine technology.
It was powered by a three-cylinder engine, an early prototype of the new generation of petrol direct injection engines. With the A2 1.6 FSI now making its début, yet another technological innovation which was first shown on the much-acclaimed Al2 prototype is thus going into volume production, underlining the role of the A2 model line as the technological avant-garde of the compact class.
FSI – the future of spark-ignition technology
FSI petrol direct injection: Audi unveiled the first production version of its new family of engines at the 2001 Frankfurt Motor Show, in the guise of the 2.0 four-cylinder unit with an output of 110 kW (150 bhp). The 1.6 FSI is now the second engine to use this pioneering form of mixture preparation.
The effectiveness of the new technology was first demonstrated compellingly in a motor racing car in June 2001: the Audi R8 which triumphed at Le Mans was likewise powered by an FSI engine, and owed its victory in that notable race in particular to the unique combination of efficiency and economy that is the result of FSI technology.
FSI engines are all-rounders: they deliver more torque and power, and are therefore palpably more dynamic, than engines with conventional indirect injection. What is more, they reduce fuel consumption by up to 15 percent.
It is no mere coincidence that such a quantum leap should seem reminiscent of the revolution in diesel technology brought about by Audi’s TDI engines. They, too, succeeded in combining high power output and an effective reduction in fuel consumption to a previously unattainable extent.
So how does an FSI engine differ from a conventional one? On this engine, fuel is not injected into the intake port, but directly into the combustion chamber. The injector, which is supplied by a high-pressure pump and common rail fuel line, is in the side of the cylinder head, and controls the injection time to within milliseconds, at injection pressures of up to 110 bar.
Stratified charge and homogeneous operation
In the stratified-charge operating mode, fuel is injected during the engine’s compression stroke and is picked up by the movement of the air that has been drawn into the combustion chamber. A movable flap in the intake manifold, the intake port and the special shape of the piston crown impart a type of movement in the air that is known as “tumble”.
The main factor contributing to the engine’s efficiency is the stratified-charge principle at part load. In other words, in this operating mode the engine only needs a fuel-air mixture capable of immediate ignition in the area around the spark plug. The remainder of the combustion chamber is filled with a leaner mixture, that is to say one with a considerable degree of excess air. As a result of this, the engine can be run with the throttle valve open. The direct injection engine also benefits from reduced heat losses,
This means that the strata of air around the ‘cloud’ of ignitable mixture isolate the latter from the cylinder and cylinder head; less thermal energy is lost via the cooling system.
The desired “stratified-charge effect” is obtained in this way: the cloud of fuel which has become swirled with sufficient air to form an ignitable mixture surrounds the spark plug at the moment of ignition.
After combustion, a layer of air insulates the ignited mixture from the cylinder wall. This cuts the amount of heat lost to the engine block and increases the engine’s operating efficiency.
In stratified-charge operation, incidentally, significantly higher lambda values related to the combustion chamber as a whole are achieved. This is essential if fuel consumption is to be reduced at low and medium engine speeds.
At full load, the fuel in injected synchronously with the air intake phase. This fills the combustion chamber homogeneously. Here again, this produces a definite reduction in fuel consumption together with higher power-output and torque figures than would be possible with indirect fuel injection. This was demonstrated on the race-winning Le Mans engine, which runs permanently in the homogeneous mixture mode.
Highly effective exhaust emission control
On the exhaust side of the engine there is one of the fundamental elements needed for efficient exhaust emission control, the exhaust gas recirculation system. This operates more efficiently than previous systems, and diverts up to 35 percent of the exhaust gas back to the engine’s combustion chambers. Two catalytic converters are provided for exhaust emission control: an underbonnet three-way converter behind the manifold, and a NOx storage-type converter under the floor pan.
The NOx storage converter has been specially designed to suit the needs of a direct injection engine, and has a NOx sensor installed at the discharge end. It is an established fact that the conventional three-way catalytic converter is unable to break down oxides of nitrogen sufficiently in the engine’s lean-burn phase; for this, the composition of the exhaust gas must be stoichiometric (14 parts air to one part fuel).
The higher levels of oxides of nitrogen that remain therefore have to be reduced to harmless nitrogen gas. This task is performed efficiently in the storage-type catalytic converter, which has a barium coating with which the oxides of nitrogen combine.
The storage-type converter is controlled by a mapped operating characteristic and by temperature. When the converter is saturated, the engine’s mixture is temporarily made richer. As a result of the increase in temperature and the enriched exhaust gas, the nitrogen oxide is released by the barium molecules and reduced to nitrogen.
To make this new form of mixture preparation and the modified combustion process possible, Audi’s engine specialists had to develop a large number of new components and assemblies specifically for this purpose. They include the following:
- The common rail fuel injection system with high-pressure injection pump
- The external exhaust gas recirculation system
- A further development of the exhaust emission control system, with a NOx storage-type catalytic converter and NOx sensor
This array of new features highlights that the new 1.6 FSI engine is far more than simply a refined version of a conventional predecessor. Its production launch in the first half of 2002 lends yet more substance to Audi’s proverbial “Vorsprung durch Technik”.
Top model in the range: the A2 1.6 FSI
Like the other versions in the A2 model line, the 1.6 FSI represents the sum total of Audi’s experience as a pioneer of lightweight design. As a result of its Audi Space Frame ASF, the A2’s aluminium body is more than 40 percent lighter than if it had been made using conventional steel techniques. That is why the A2 uses less fuel than other vehicles in this class that are capable of a similar performance. Its low weight makes it particularly agile.
With its striking shape, the A2 moreover reinforces Audi’s claim to set new standards in the field of design. The progressive outline also signals the utterly distinctive character of an innovative vehicle concept with which Audi has once again demonstrated its credentials as a technological trendsetter.
For all its compact exterior, which measures just 3.83 metres in length, the A2’s interior nevertheless feels “grown-up” in every respect – it is outstandingly spacious, in fact. Its width of 1.67 metres and height of 1.55 metres, and above all its superior space efficiency, mean that there is a surprisingly large amount of space in the A2. The “space floor concept”, with a rear footwell that is sunk in relation to the front footwell, provides significantly more space for rear passengers, ensuring that they can maintain a superbly ergonomic, relaxing seated posture.
The increase in engine output compared with the 1.4 version is attributable to various modifications in every department. For instance there is a larger rear spoiler, which adjusts the refined aerodynamics of the A2 body in line with its higher top speed.
The running gear, too, has been modified to reflect the higher performance of the top A2 version. Specially defined spring and damper rates establish a perfect balance between maximum agility and compelling comfort in all driving conditions.
The A2 1.6 FSI also has disc brakes at the rear, to provide effective braking action at any time. And the increased capacity of the fuel tank, which now holds 42 litres, means that the car is capable of an operating range of more than 700 kilometres.
The A2 1.6 FSI is naturally available in a wide array of colour and equipment versions, lending the entire model line an exclusive, sporty flavour.
[source: audi-mediaservices.com]
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