This Week:

• Nissan Displays Modified 350Z Sports Cars and Other Performance Products at 2002 SEMA Show
  .
• Chrysler Group Debuts Vehicle Excitement Team And Three New Show Cars at SEMA Event
  .
• Buick Adds Rainier SUV To Product Line
  .
• The Phaeton: its 4MOTION all-wheel drive and air suspension mean active safety and ride quality at the highest level
  .
• PSA Peugeot Citroën to Build a New Assembly Plant in Europe
  .
• Ford Design VP J Mays to Be Featured in Los Angeles Museum Exhibition
  ... .
• BMW GROUP NA Sales Pass 200,000-Vehicle Threshold
  .
• DaimlerChrysler: smart Variant to be Produced in Brazil
  .
• Toyota Announces Semi-Annual Operating Results
  .
• Shanghai GM To Export Engines To Canada
  .

   

© 1998 - 2002 Copyright & 
Disclaimer
Automotive Intelligence,
www.autointell.com
All Rights Reserved .
For questions please contact
editor@autointell.com  

News of November 06, 2002

The Phaeton: its 4MOTION all-wheel drive and air suspension mean active safety and ride quality at the highest level

Volkswagen Phaeton

• 4MOTION: all-wheel drive for supreme safety and dynamic road travel
• 4MOTION: an innovative system that is superior to classic rear-wheel drive
• Air suspension: the car's body is lowered automatically above 140 km/h
• Air suspension: a combination of ride comfort and dynamism that sets new standards

Wolfsburg - Scarcely any other large luxury saloon on the market has such convincingly high active safety reserves as the Volkswagen Phaeton. Taking the 309 kW (420 bhp) top model, the Phaeton W12, as an example: in view of its immense power output is has permanent all-wheel drive as a standard feature. This system, known as 4MOTION, not only brings outstanding dynamism and refinement to every journey but also guarantees maximum active safety even if weather conditions are extremely poor.

Its dynamic behaviour on the road is rendered even more supreme by another technical development: air suspension at all four wheels. This is a standard feature on every Phaeton, including the front-wheel-drive Phaeton V6 with its very neutral handling characteristics. Every Phaeton W12 therefore has both systems: four-wheel air suspension and 4MOTION all-wheel drive, a combination of two top technologies which will appeal to the active driver and which makes it one of the safest and most comfortable twelve-cylinder saloon models in the world.

4MOTION all-wheel drive in detail

Among the specific advantages of 4MOTION compared with drive to the rear wheels alone is distinctly improved traction and handling. In particular when critical load-reversal reactions occur, all-wheel drive demonstrates its advantages, and is far less dependent on electronic traction control systems - although the Phaeton W12 is of course also equipped with ESP as standard. The 4MOTION driveline distributes engine torque variably, from 0 to 100 %, between the front and rear wheels according to the amount of tyre grip available, so that traction and lateral locating force at each wheel always remain as high as possible.

This important torque distribution function is performed by a Torsen centre differential, which reacts to even slight differences in the speed of rotation of the front and rear halves of the driveline. Thanks to this differential, which is integrated into the 4MOTION transmission, and to the standard torque split of 50 : 50 between the front and rear axles, the Phaeton W12 can be regarded as a true all-wheel-drive vehicle. The 4MOTION driveline transmits the power flow from the planetary gear train in the car's standard five-speed automatic transmission to the input side of the Torsen differential.

there the torque is normally transmitted equally via spur gears to the propeller shaft leading to the rear axle and via an intermediate gear stage to the front axle. The entire driveline is extremely rigid, so that noise levels are low even when driving off from a standstill or when load reversals occur. The actual locking-action differential is a Torsen PAT with the differential gears located parallel to the axis of rotation.

Four-wheel air suspension in detail

Photos: VW

Volkswagen has succeeded in giving the Phaeton excellent dynamic safety and a high degree of dynamism without sacrificing ride comfort, thanks to the standard air springs in combination with four-link front suspension and trapezoidal-link rear suspension.

The chassis development engineers' aim was to create a suspension system that satisfies the highest standards of both journey comfort and road dynamics. Air suspension with controlled damping is ideal for the purpose, with many advantages not possessed by a conventional system with steel springs.

The air suspension's ride height control function, which maintains a constant body height regardless of load, enables the springs to be given softer ratings for maximum comfort and also permits the cars body to be lowered by a specific amount at high speeds; this also has the effect of reducing fuel consumption. Air suspension also makes the car ride and handle better on poor surfaces.

The physical characteristics of air suspension enable the spring rate and the vehicle's static ride height to be varied automatically in accordance with the load being carried: this is the classic self-levelling function associated with air suspension, and ensures that the occupants enjoy an equally comfortable ride regardless of the total load. In addition, the vehicle's dynamic characteristics vary less when it is heavily laden. Since the damping action is also continuously variable, ride comfort and driving safety are both significantly improved, and even the most extreme handling situations can be mastered more effectively with the aid of changes to the damping characteristics.

The air suspension itself consists in detail of the following basic elements: four air suspension struts, one at each wheel, the air supply pump unit, a pressure reservoir, a control unit, four level sensors at the front and rear axles, three acceleration sensors on the car's body and another four mounted on the suspension elements. The key elements in the system are the four air spring modules. The externally located bellows are specially shaped for smooth initial response whenever wheel movement occurs. The desired low spring rate is assured by providing additional reservoir volume and by special shaping of the pistons, which has a positive effect on the air spring's dynamic behaviour.

In addition, the damping force exerted at each wheel can be varied within a few thousandths of a second to match actual needs by an electric control valve integrated into the piston of each hydraulic shock absorber. The optimum damping force, which depends on the car's direction and stability, is determined among other factors by the signals from wheel acceleration sensors mounted on the shock absorbers themselves, and three acceleration sensors on the car's body. This 'intelligent' technical system makes this large luxury saloon exceptionally agile in its handling despite the high level of journey comfort which it provides.

The electronically controlled shock absorbers identify the driving situation and vary the damping characteristic over a specific range, in accordance with a mapped characteristic. If the Phaeton is being driven in a highly dynamic manner, firmer shock absorber settings are adopted. This reduces body roll and shifts the Phaeton's road behaviour towards a more sporting style of driving. If on the other hand, the car is driven in a relaxed manner on largely straight roads, the shock absorbers are given softer settings for maximum ride comfort. These changes take place steplessly and within a fraction of a second.

Thanks to this air suspension and dynamic damping system, the suspension settings retain the car's dynamics without any reduction in the occupants' ride comfort. The suspension strut support mounts are designed located in such a way that no lateral forces reach the shock absorbers. This makes their initial response more sensitive and contributes to the Phaeton's exceptional ride quality.

Three body ride heights can be selected for the Phaeton: Normal (NN), Raised (HN, 25 mm higher than NN) and Low (TN, 15 mm below NN). The low level is selected automatically according to the car's road speed (above 140 km/h), so that its dynamic road behaviour and fuel consumption are optimised. The driver can also select suspension settings manually: the NN and HN positions and four shock absorber settings (Comfort, Basic, Sport and Sport 2) are available.

Damping control makes use of the 'skyhook' principle, the general aims of which are to minimise body movements, guarantee a constant ride height regardless of road conditions and thus ensure both optimum occupant comfort and maximum tyre grip. This combination of the 4MOTION all-wheel drive and air suspension with electronic damping control represents state of the art technology in this area - and therefore reflects the principle adopted for every aspect of the Phaeton concept.

(Nov. 1, 2002)

[Homepage] [ News] [ Companies] [ Management] [ Publications] [ Events] [ Careers]
[Services] [Discussion] [ Guestbook] [ Search]