The starting pistol is about to be fired for a highly talented young sprinter: the new top version in the A2 range, the A2 1.6 FSI, accelerates from 0 to 100 km/h in just 9.8 seconds. This lightweight athlete with aluminium body and Audi Space Frame ASF reaches a top speed of 202 km/h. But it is not just these performance figures that make the A2 1.6 FSI such an impressive new car. It is also the first Audi production model to be powered by a spark-ignition engine of the next generation: the bonnet conceals a 1.6-litre unit with FSI petrol direct injection that develops 81 kW (110 bhp).
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.
The lively 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 (overall fuel consumption according to 1999/100/EC). Bearing in mind its performance figures and ample interior space, with room for up to five occupants, this is an unbeatably low value.
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 data, this figure qualifies the A2 1.6 FSI as a long-distance vehicle: with high average speeds, it can cover considerable distances without stopping to refuel.
Two very difference ancestors: the Al2 and the R8
A straight line descends from the A2 1.6 FSI to the ancestor of the entire model series, the Al2 study which Audi presented at the 1997 Frankfurt Motor Show. This vehicle already incorporated essential features of the revolutionary aerodynamics and space concept for which the A2 production models ultimately became renowned; as well as an all-aluminium body based on the ASF principle, it already had pioneering engine technology.
It was powered by an early prototype of the new generation of petrol direct injection engines – in the form of a three-cylinder unit. The launch of the A2 1.6 FSI will consequently see a further technological innovation that was announced by the much admired Al2 study introduced into volume production: the A2 series is thus proving once again to be the technological avant-garde of the compact class.
By contrast, this new car’s relationship to a further family member is not immediately obvious at first glance. But the Le Mans winner from 2001, the Audi R8, is more closely related to the new A2 1.6 FSI than its purpose and visual differences would have us believe. This racing car was also powered by an engine with FSI direct injection.
For the winning team, the use of this new technology meant not only a much higher performance potential, but also a reduction in fuel consumption by around eight percent – the prerequisite for correspondingly longer distances between refuelling stops. But that’s not all. The drivers also praised the fact that an FSI racing engine allows them to control the power much more precisely than is generally the case with such power units.
FSI – the future of spark-ignition technology
When the Audi R8 with FSI engine won the Le Mans 24 Hours, this was not least the result of the unique combination of power and economy that characterises FSI technology.
FSI engines are all-rounders: they deliver more torque and power, and are therefore palpably more dynamic and efficient than engines with conventional indirect injection. What is more, they make it possible to reduce fuel consumption by up to 15 percent in production vehicles.
A quantum leap that is reminiscent of the revolution in diesel technology brought about by the TDI engines developed by Audi, and not without good reason: here too the company succeeded in combining high power and clearly reduced fuel consumption to a previously unknown extent.
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. These include:
- a common rail fuel injection system with high-pressure injection pump
- a four-valve cylinder head with laterally located injector and an intake port divided by a tumble plate
- two-position tumble control
- an external exhaust-gas recirculation system
- an optimised emission treatment system, with NOx storage-type catalytic converter and NOx sensor
- two-line exhaust-gas cooling with radiation cooler
The greatest challenge apart from exhaust-gas treatment proved to be the implementation of the necessary software in the engine control unit. This is because the many maps and the transitions between the operating states call for a computing capacity more than twice the norm.
Only with the aid of sophisticated computer simulations was it possible to match the complex, three-dimensional maps sufficiently.
This array of new features makes it clear that the new 1.6 FSI engine is far more than simply a refined version of its conventional predecessors. Its production start in the Audi A2 marks the start of a new era for Audi spark-ignition engines and lends yet more substance to Audi’s proverbial “Vorsprung durch Technik”.
Two operating states
So how does FSI technology differ in design terms from a conventional engine?
The term “petrol direct injection” makes the most significant feature clear: in contrast to indirect injection, the fuel is injected directly into the combustion chamber.
The injector, which is located in the cylinder head on the intake side, is supplied by a high-pressure pump driven by the camshaft and a single distribution pipe for all cylinders, the common rail system. The injector controls the injection time to within thousandths of a second, at injection pressures of up to 110 bar. By comparison, indirect injection operates at a maximum of eight bar.
A further special feature can be found in the intake port – the so-called “tumble flap”. On the 1.6 FSI engine this can be placed in two positions, thus controlling the movement of the incoming air.
With the flap in the open position, the air passes by unobstructed. In the second position the flap moves against the tumble plate, thus shielding the lower part of the intake port. In this way it channels the intake air via a controlled path into the combustion chamber and to the piston crown.
This makes two different operating modes possible – these are the fundamental requirement for the versatility of the FSI principle: homogeneous and stratified-charge operation. Depending on load status and accelerator position, the engine electronics always switch to the optimum mode – without the driver noticing.
Homogeneous operation – more power, less fuel
A conventional indirect injection engine produces a petrol-air mixture in the entire combustion chamber with an ignitable ratio of 14.7 : 1 (lambda = 1).
An FSI engine also operates in this mode, known as “homogeneous operation”: namely whenever the engine is required to produce a high power output.
At full load, the fuel is injected synchronously with the air intake phase. This fills the combustion chamber uniformly. However, due to the precision of the injection process, the extremely fine atomisation and the internal cooling effect when the fuel evaporates directly in the combustion chamber, the FSI engine can operate at a much higher compression ratio than an indirect injection engine (1.6 FSI: 12.1:1). This results in greater efficiency.
In other words, even in the homogeneous mode it is possible to achieve a significantly lower fuel consumption coupled with much higher power and torque figures – this was demonstrated in impressive style by the race-winning Le Mans engine, which runs permanently in the homogeneous mixture mode.
Stratified charge: maximum reduction in fuel consumption
Stratified-charge operation at part load, however, is essential for realising the new engine’s fuel-saving potential. In this mode an ignitable mixture is only present in the area around the spark plug; in the rest of the combustion chamber there is a clear excess of air.
In the stratified-charge operating mode, fuel is not injected until the engine’s compression stroke. It thus passes directly into the air in the combustion chamber which, due to the diagonal position of the flap in the intake port on the one hand and the special shape of the piston crown on the other, has been set in a motion that is known as “tumble”.
This controlled tumble motion also enables the required stratification to be achieved: the cloud of fuel which has become swirled with sufficient air to produce an ignitable mixture is kept to a confined volume and reaches the spark plug at the moment of ignition.
In stratified-charge operation, significantly higher lambda values – which means a lean mixture – related to the combustion chamber as a whole are achieved. This, together with reduced flow restrictions, is essential if fuel consumption is to be reduced at low and medium engine speeds.
An additional benefit: after the start of combustion, a layer of air insulates the ignited mixture from the cylinder wall. The amount of heat lost via the engine block is cut as a result. This also reduces energy losses and increases the engine’s operating efficiency.
Strictly speaking the 1.6 FSI engine has a third operating state: the lean homogeneous mode. In this transitional phase between homogeneous and stratified-charge operation, the injection and combustion processes are the same as for pure homogeneous operation. However, the engine operates with an excess of air. This enables fuel consumption to be reduced further compared with pure homogeneous operation where lambda = 1.
Highly effective exhaust emission control
In the past the subject of NOx emissions posed a major obstacle for the developers of petrol direct injection engines based on the stratified-charge principle. Due to the excess of air, it was not possible to reduce the resulting oxides of nitrogen completely to nitrogen gas using a conventional catalytic converter.
Audi has tackled this problem on its 1.6 FSI engine with a whole series of measures.
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.
Controlled by the engine electronics and regulated by the exhaust gas recirculation valve (external exhaust gas recirculation) and variable intake camshaft (internal exhaust gas recirculation), it diverts up to 35 percent of the total exhaust gas back into the combustion chamber. This helps to reduce the combustion temperature. Untreated NOx emissions are consequently cut by up to 70 percent during stratified lean-burn operation.
With NOx storage converter
The 1.6 FSI engine is fitted with two catalytic converters for exhaust emission control: the familiar underbonnet three-way converter behind the manifold, and an NOx storage-type converter under the floor pan.
This has been specially designed to suit the needs of a direct-injection engine. An NOx sensor is 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 (14.7 parts air to one part fuel).
The higher levels of oxides of nitrogen that remain after the underbonnet converter 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 made richer for a short time. This raises the temperature of the slightly rich exhaust gas so that the barium molecules in the converter release the oxides of nitrogen, which are then reduced to nitrogen. This process goes unnoticed by the driver.
Exhaust gas cooling for greater efficiency
NOx storage-type converters operate most efficiently between around 250 and 500 degrees. This range is therefore the prerequisite for the lean-burn operation of the petrol direct injection engine since NOx emissions are particularly high in this mode.
In order to guarantee that exhaust gas temperatures remain within this range even at high speed, the exhaust system of the A2 1.6 FSI is fitted with an exhaust gas cooler which is located in front of the NOx storage-type converter. To improve cooling efficiency particularly when exhaust gas temperatures are high, the heat sink is designed as a radiation cooler.
This highly efficient form of exhaust gas cooling means that the lean-burn operating range can be extended significantly to include higher engine speeds, thus increasing the overall efficiency of the engine quite considerably.
The top athlete in the model series: A2 1.6 FSI
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 75 bhp, the range includes a 1.2 TDI version, which became the world’s first five-door, three-litre car when it was launched in 2001. This version combines advanced technology, economy, ample space and driving pleasure 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 sheer driving pleasure.
Lightweight design and performance
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 aluminium body of the A2 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. And its low weight makes it extremely agile, especially in conjunction with the new top-of-the-range engine version.
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 interior of the A2 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 room 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.
Technical perfection for the top model
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 small spoilers in the front wheel arches serve the same purpose.
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.
High standards of safety
As on the Audi A8, the aluminium body built according to the Audi Space Frame ASF principle constitutes the ideal basis for a high passive safety standard. This high-strength frame structure protects the occupants like a cocoon and impact energy is reduced particularly effectively.
With two airbags at both the front and sides, seat belt tensioners and belt-force limiters for all seats, the Audi A2 offers its occupants a high level of safety. The optional SIDEGUARD head airbags set a new benchmark in this class.
In many side or angled impacts SIDEGUARD provides additional protection for the head and neck region of outboard passengers. This airbag system cushions the side window areas and A- and B-posts almost completely.
Equipment: both functional and luxurious
The Open Sky System on the A2 is a real eye-catcher – both inside and outside the car. This glass sunroof has a much larger opening and consequently lets in considerably more light and air for the occupants than conventional sunroofs.
The Multibox System has also been specially developed for the Audi A2. As well as the Space Floor Box and the centre console box with integral cup holders, the package also includes a 12-volt power socket in the luggage compartment. The box can also be flush-fitted in the rear footwell, which is particularly deep thanks to the Space Floor Concept. This additional storage space accommodates toys, drinks or handbags. One of this stable container’s most practical secrets is that it can also be used as a picnic basket or outdoor seat.
There are other items of optional equipment for the Audi A2 which are luxurious, but also practical and highly informative. For example the navigation system Plus, which has a monitor that may be used for TV viewing when the car is stationary.
Automatic air conditioning, which is regulated depending on the position of the sun, is an optional extra for the Audi A2 that maintains the ideal temperature. The new technology cuts energy consumption considerably compared with conventional systems.
For a very distinct hint of luxury, Audi A2 owners can choose leather upholstery and trim for the interior in a choice of six colours. Customers have the choice between elegant black, light beige or light grey, but also between bright red, blue or yellow.
Together with one of the colour-coordinated leather-covered steering wheels that are also available as optional extras, this colour scheme adds a dynamic and elegant note to the interior. This Pearl Nappa leather option or a combination of leather/Alcantara can also be combined with front sports seats that provide excellent lateral support.
For the youngest A2 passengers Audi offers a range of child seats suitable for all ages, which are reliably secured in the back of the car using the standard ISOFIX mountings.
Audi also offers attractive equipment packages for the A2 1.6 FSI. The Style Package includes four 15-inch cast alloy wheels of 6-arm design, remote control for the central locking, leather trim for steering wheel, gear lever and handbrake grip and height adjustment for the front seats. The Style Package Plus even contains 17-inch cast aluminium wheels of 9-spoke design with size 205/40 ZR 17 tyres.
The Advance Package comprises a number of popular extras such as automatic air conditioning and metallic paint. The High Tech Package contains the large-area glass sunroof known as the Open Sky System, the Acoustic Parking System and preparation for a mobile phone.
[source: audi-mediaservices.com]
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