Page 1 - Design
Page 2 - Engines and transmissions
Page 3 - Engines and transmissions (cont.)
Page 4 - The chassis
Page 5 - The chassis (cont.)
Page 6 - The body
Page 7 - Comfort and communication electronics
Page 8 - Comfort and communication electronics (cont.)
Page 9 - Standard equipment
Page 10 - Optional equipment
The TDI engines
3.0 TDI
A genuine power pack is being introduced in the Audi A6 Avant in the guise of the three-litre six-cylinder unit. Compared with the competition, this engine offers truly impressive power and torque potential: 225 bhp and 450 Nm. Maximum torque is available just above idle speed, starting at a mere 1,400 rpm and giving the driver forceful acceleration at all speeds.
Despite having a torque-converter transmission, this means performance on the road that even many a sports car will find hard to match: the A6 Avant 3.0 TDI accelerates from 0 to 100 km/h in just 7.3 seconds, and reaches a top speed of 240 km/h.
Further fortes are the engine's highly efficient noise management and compliance with the strict EU4 emissions standard.
Featuring turbocharger technology and map-controlled, cooled exhaust-gas recirculation, this V6 four-valve power unit is the first six-cylinder TDI in Audi's new family of V-configuration engines. Both the camshafts and the oil pump, incidentally, are driven by chains.
Like all engines in Audi's new V-generation, the V6 TDI has extremely compact dimensions: engine length, for example, measures a mere 444 mm. This is also an important step in view of achieving an overall engine weight of just 219 kg, making the 3.0 TDI one of the lightest V6 diesels in the world. This benefits the power-to-weight ratio and the weight distribution in equal measure – two characteristics that are of central importance for the driving dynamics of the new A6 Avant 3.0 TDI quattro.
Common rail technology with piezo inline injectors
Mixture preparation is the task of a latest generation common rail system featuring a high-pressure pump and a rail for each row of cylinders. This increases maximum injection pressure to 1,600 bar, 250 bar more than with previous common rail systems.
This high injection pressure results in even finer atomisation of the fuel and therefore in better mixture preparation and more efficient combustion.
The piezo injectors are undoubtedly the most important innovation of the new common rail system. The injection process makes use of the piezo effect: a voltage is applied to ceramic which changes its crystal structures. The result is a minimal geometric change which – supported by a hydraulic element – mechanically triggers the opening of the injector needle.
The piezo injectors offer multiple advantages compared with conventional solenoid valves. The moving mass at the injector needle is for instance reduced by no less than 75 percent, from 16 to 4 grams in each case. This enables considerably smaller and more precisely metered injection quantities. At the same time, piezo technology allows a higher injector needle speed.
The number of injection processes per combustion cycle can thus be varied almost at will. Audi’s TDI development engineers opted for up to five injection processes for the 3.0 V6: in addition to the main injection process, double pilot injection takes place at the lower end of the speed range and single pilot injection in the medium speed range. On top of this, single post-injection takes place up to around 2,500 rpm and at maximum part-load.
This strategy produces both lower emissions and a smoother combustion process, the benefits of which are most immediately apparent in the engine's acoustic behaviour. The 3.0 TDI engine is not only much quieter and smoother than its predecessor, it now unquestionably serves as the benchmark in its class.
Turbocharger with two intercoolers
For optimum charging of the combustion chamber in all operating conditions, the six-cylinder 3.0 TDI has a turbocharger accommodated inside the engine's "vee" to make optimum use of the available space. And to enhance efficiency to the highest level, the temperature of the intake air is reduced by two intercoolers running in parallel, any loss of pressure being kept to a minimum.
The exhaust gas is purified by a close-coupled primary catalytic converter – located close to the turbocharger – and the main converter under the floor. As a result of all these measures, the A6 Avant 3.0 TDI is the first car in the diesel executive class that easily undercuts the limit values of the EU4 standard.
One feature of the new engine that is undoubtedly as welcome as its efficiency at reducing emissions is its impressive fuel economy. Its overall consumption over 100 kilometres is just 8.0 litres of diesel. In practice this obviously means a very significant cruising range, the A6 Avant 3.0 TDI quattro being able to cover almost 1,000 kilometres on one tank of fuel.
The Audi A6 Avant 3.0 TDI comes as standard with quattro permanent four-wheel drive and either a 6-speed manual gearbox or a 6-speed automatic transmission complete with tiptronic function.
The 2.7 V6 TDI
In addition to the 3.0 TDI, the A6 Avant is starting out with a further representative of the latest V6 TDI engine generation with common rail system and piezo inline injectors: the 2.7 TDI.
Like its big brother, which has a capacity of three litres, it makes use of the latest injection technology and consequently already undercuts the demanding EU4 emission limits, which will not take effect until 2006, even without a diesel particulate filter.
A new crankshaft with the stroke reduced by 8.3 millimetres, new connecting rods and different pistons result in an overall swept volume of 2,698 cc. The key data with regard to its performance are an output of 132 kW (180 bhp) across an engine speed range of 3,300 to 4,250 rpm and a peak torque of 380 Nm available from just 1,400 rpm all the way up to 3,300 rpm.
These measures result not only in high performance and an enormous torque plateau, but also in low fuel consumption (7.0 litres per 100 kilometres), extremely low emissions and outstanding acoustics. It is especially in this latter area that the new engine undoubtedly represents the new benchmark in this class.
As a result the driver will notice a spontaneous response and tremendous pulling power even from the lowest revs. The 100 km/h mark is passed after just 8.3 seconds on the way up to a top speed of 225 km/h. But it is the mid-range sprints that are the outstanding discipline of this new high-performance engine, which is supplied in combination with front-wheel drive and 6-speed manual gearbox.
2.0 TDI
Driving pleasure and supreme economy, refinement and environmental compatibility: the 2.0 TDI four-cylinder with pump-injector technology, one of the most modern engines in its class, is making its debut in an executive class Avant as a highly talented all-rounder.
Again, the particular strengths of this engine are its high output and powerful torque, combined with equally impressive economy. The Audi A6 Avant 2.0 TDI is easily able to cover more than 1,100 kilometres on one single tank of diesel.
A maximum output of 103 kW (140 bhp) and peak torque of 320 Nm, available between 1,750 and 2,500 rpm, make this the most powerful and dynamic four-cylinder diesel that Audi has even installed in its cars. Performance on the road is correspondingly impressive: the 2.0 TDI with 6-speed manual gearbox accelerates to 100 km/h in just 10.6 seconds and continues on up rapidly to its top speed of 205 km/h.
Two other key strengths of the 2.0 TDI are its low fuel consumption – 6.1 litres of diesel fuel per 100 km (overall value) – as well as compliance with the EU4 emissions standard.
In addition, the four-cylinder unit gives the new Audi A6 Avant a standard of smoothness and refinement which certainly befits an executive estate of this calibre. A balance shaft module with two shafts rotating in opposite directions helps to reduce engine vibrations extremely effectively.
The front-wheel-drive Audi A6 Avant 2.0 TDI will be available with a 6-speed manual gearbox or multitronic from mid-2005.
Transmissions
The low fuel consumption and excellent dynamic performance offered by the new Audi A6 Avant benefit from the standard usage of 6-speed manual and 6-speed automatic transmissions.
Six gears featured as standard
The manual versions of the new Audi A6 Avant – as well as the saloon version – come with Audi's latest generation of ML transmissions, the abbreviation ML standing for Manual/Longitudinal.
This gearbox is noted for its extremely precise, crisp, short gearshifts. Thanks to a special mount for the selector forks, the gear lever is effectively protected against driveline vibrations; the driver does not feel the gear lever trembling at all.
Internal friction reduced by a series of measures increases the efficiency of the manual gearbox. This means that engine power can be converted even more efficiently into forward propulsion.
The 6-speed tiptronic
A six-speed tiptronic transmission is available for the very high-torque 4.2 V8, 3.2 FSI and 3.0 TDI power units in conjunction with quattro permanent four-wheel drive. Having already made its debut in the high-performance Audi S4 sports model, this transmission converts the engines’ power potential into a superior symbiosis of dynamism and operating convenience.
Weight reduction, rapid gearshifts and an optimised shifting strategy make sure that the convenience of the automatic transmission is combined with the sports performance so typical of the A6.
Compared with its five-speed predecessor, the new six-speed gearbox is 14 kilograms lighter; its overall weight is a mere 115 kilograms.
Again compared with a five-speed automatic transmission, the spread of gear ratios is up by 18 percent on average. This means a much improved accelerating performance in the low gears and a clear reduction in engine speed and consequently a reduction in both noise level and fuel consumption at high speeds.
The shifting speed of the new 6-speed tiptronic has also been significantly optimised. The driver benefits from more spontaneous gear changes particularly when downshifting. In addition, the fact that the engine automatically double-declutches further increases agility.
Both in stage D and in the S sport program, the electronics respond efficiently to parameters such as lateral and longitudinal acceleration as well as to the movement of the accelerator pedal. This helps to prevent any unwanted upshifts when cornering.
Continuously variable multitronic
After making its production debut successfully in the A6 2.8 in the year 2000, Audi's continuously variable multitronic automatic transmission now also offers its superior qualities in the new A6 Avant, combining the benefits of a manual gearbox with those of a multi-stage automatic transmission. Fortes typical of multitronic are smooth but very dynamic acceleration as well as convenient operation and the efficient transmission of power.
The high standard of operating convenience offered by multitronic exceeds that of a conventional converter-type automatic transmission, while in terms of dynamic performance and economy, multitronic can by all means be compared with a manual gearbox. And if drivers wish to choose the appropriate transmission ratio themselves, they can do so by means of paddles on the steering wheel – now providing no fewer than seven predefined speeds.
Numerous reinforcements and adjustments, as well as optimised cooling, serve to significantly enhance the performance of Audi's continuously variable automatic transmission. The multitronic can now transmit torques as high as 330 Nm.
Modified for the new Audi A6 Avant, the multitronic variator spans an even wider range of gear ratios: the overall spread between the highest and the lowest gears is now 6.25, virtually ideal for such a transmission. This on the one hand permits dynamic, sports-style acceleration using the largest possible ratio, while on the other hand the engine's fuel-saving potential is fully exploited using the smallest ratio.
A further special feature is the ability of the electronics to emulate the functions of a manual gearbox. For the latest multitronic version, Audi has opted for no fewer than seven forward gears which the driver can activate using the one-touch function in the second shift plane or by pressing the shift paddles on the steering wheel (optional).
These seven gearshift stages are memorised by the system as fixed shift programs. Depending on which gear the driver selects, the controller is supplied with the ratio as a set point, which it establishes and maintains. Even these manually prompted gearshifts take place smoothly and jolt-free, satisfying the desire for sports performance thanks to continuous adaptation.
A new multitronic function in the Audi A6 Avant is the starting assist function: a simple press of the brake pedal and the service brake automatically prevents the car from rolling back on a gradient. It is also released automatically as soon as the driver opens the throttle to pull away again.
quattro permanent four-wheel drive
quattro permanent four-wheel drive – a drive principle that has been enjoying success in both motorsport and production vehicles alike for the last 25 years – is a typical feature of all high-performance Audi models. More than 1.8 million Audi quattro models had come off the production line by the beginning of 2005 alone – a figure that speaks for itself.
quattro ensures excellent traction and stable cornering, and minimises the effect of propulsive forces on the car's self-steering properties. This is a precondition for high cornering speeds and a high level of dynamic stability.
A Torsen differential in the new Audi A6 Avant – with its longitudinally installed engines – automatically ensures the optimum distribution of power between all four wheels. The name "Torsen" is a contraction of the two terms "torque" and "sensing". The Torsen differential is a self-locking worm gear.
The advantage of this is that the locking action is only prompted by the driveline. Yet this type of differential accommodates differences in speed when the brakes are applied and when cornering. Normally the power is split 50:50 between the two pairs of wheels, but in extreme cases 75 percent of propulsive power can be diverted to either pair.
Related entries:
New Audi A6 - In Depth
Source URL: http://nensycarblog.blogspot.com/2008/01/new-audi-a6-avant-in-depth_1955.html
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