The A4 3.2 FSI quattro and 2.0 TFSI quattro are optionally available with sixspeed Tiptronic. This classic automatic transmission, with the Sport program and the additional manual-shift mode, has been thoroughly revised in design in the transfer-case and torque-converter areas.
The torque converter now is equipped with a novel form of two-stage torsional damper that permits the lock-up clutch to remain engaged for long distances, which boosts overall efficiency and reduces fuel consumption.
When the car is at a standstill, a controlled drive-off clutch disconnects the transmission from the engine even if the selector lever remains in position D. As soon as the driver releases the brakes, this clutch is engaged.
In the new Audi A4, the Tiptronic transmission operates even more dynamically than in the previous model; it reacts more rapidly and performs shifts much faster without any penalties in terms of smoothness. The reasons for these improvements are the improved layout of the oil passages used to fill the converter and more powerful software for the Dynamic Shift Program (DSP).
For all the front-wheel-drive versions of the new A4 (Avant is quattro-only for USA, Tiptronic only, 2.0 TFSI only with 211 hp), Audi offers the continuously variable multitronic exclusively with the 2.0 TFSI powertrain. It combines the advantages of manual transmission with those of torque-converter transmission and, due to its both extremely comfortable and highly dynamic acceleration, it provides sporty driving comfort.
A great many improvements reduce its internal losses even further. By permitting the engine to run continuously in its optimal operating range, multitronic allows for an extremely frugal driving style.
The new variator also contributes to this high efficiency by allowing a wider spread of transmission ratios – increased to 6.73 from the previous 6.25 between the highest and lowest ratio. In the highest ratio the A4 accelerates powerfully, whereas the lowest enables the engine’s fuel-saving potential to be fully utilized by means of low engine speeds. Due to its reduced start-up ratio, the A4 moves off powerfully from a standstill. With its adaptive control system, the transmission varies its settings according to current driving style and road conditions.
The D mode provides classic, continuously variable transmission. The S sports program operates with shorter ratios; when accelerating, the system shifts through eight specific, pre-programmed ratios in succession – an impressively sporty process. In one-touch mode, the third operating mode, the driver can actively shift between the eight speeds, either using the selector lever or – optionally – using shift paddles behind the steering wheel.
Unsurpassed: quattro permanent all-wheel drive
The new Audi A4 2.0 TFSI and 3.2 FSI transmit their power to the road by way of quattro permanent all-wheel drive; for the 2.0 TFSI, quattro technology is standard for Avant and optional for the sedan for North America. It delivers the supreme capabilities that have become an Audi trademark – enhanced dynamics, traction, safety, and directional stability. The quattro versions of the new Audi A4 are supremely stable under all conditions.
For the new Audi A4, the key element in the quattro driveline is a self-locking center differential. It operates purely mechanically and reacts instantly to changes in the driving situation, allowing the system to produce sporty and highly agile driving dynamics. Under normal driving conditions, 40 percent of propulsion is distributed to the front wheels and 60 percent to the rear wheels. Whenever required, the self-locking center differential redirects most of the torque to the axle with better traction. This means that when driving at the handling limits, the new Audi A4 often does not require ESP or EDL to intervene, and there are also significantly fewer brake ESP or EDL braking interventions.
The dynamic suspension
The dynamic suspension on the new Audi A4 once again sets new standards, combining precision and dynamism with a high level of stability and a supreme sense of control. It has been entirely redesigned, with the suspension mounts, steering, wheels and brakes developed for top performance and many aluminum components used to reduce weight and thus keep unsprung mass to a minimum. The innovative Audi drive select control system makes the driving experience even more compelling.
The new five-link front suspension greatly contributes to this technical advance. By moving the differential to the front and the clutch back, the design engineers were able to reposition the front axle 154 millimeters (6.06 inches) further forward. Together with the relocation of the battery to the trunk, this solution ensures an excellent front to rear axle-load balance. Even at a standstill, the new Audi A4 displays its principal personality trait: the wide stance – 1,564 mm (61.57 inches) at the front, 1,551 mm (61.06 inches) at the rear – and the large wheels round off the picture of sporty dynamism. On the road, drivers will find that the A4 is the sportiest of its competitors. It responds promptly and willingly to steering movements, remains stable, and when the handling limits are reached exhibits a slight understeering tendency which the driver can control easily.
A solid base: The front suspension subframe
The largest chassis component of all is the subframe for engine and front suspension. It is made of aluminum and rigidly bolted to the front end of the car. Due to its high rigidity, steering forces are applied without lag. On the new Audi A4, aluminum also is used for the bearing mount that links the upper suspension control arms with the body and for the pivot bearing.
The front suspension is made up of five links per wheel – a support link and a control arm at the bottom and two control arms at the top. The fifth link – the track rod – connects the steering box and the pivot bearing. All these links are made of forged aluminum, which ensures low unsprung weight, and provides ultra-precise wheel control and a high level of crash safety. The tubular anti-roll bar also helps to save weight.
The five-link suspension can handle longitudinal and lateral forces separately. In the lateral direction, the bearings are rigid to promote sporty precision and high cornering speeds. Longitudinally, however, they act with supple subtlety. In this way, dynamism and ride comfort go hand in hand.
Breakthrough: The low-mounted steering box
The steering system also has been thoroughly revised. The decisive step is the repositioning of the steering box. It was high up and fairly far back on the predecessor model – now it is far in front and placed low, on the subframe just below the front axle. Since the steering impulse now is transmitted directly to the wheels by the track rods, the steering response is very spontaneous. The steering column is bolted to the cross-member below the windscreen and to the bearing mount on the firewall, which further increases precision.
With an overall ratio of 16.1:1, the steering of the new A4 is sporty and direct. It provides precise, well-differentiated feedback from the road, and the drive forces and jolts are barely perceptible. The front suspension kinematics provide for precise centering of the steering, which adds to the sense of steering accuracy around the straight-ahead position.
The steering – a rack-and-pinion construction – was placed in an aluminum housing. A controlled-output vane-type pump supplies the necessary hydraulic energy. Unlike conventional power-steering pumps, which circulate a large volume of oil internally, it delivers only as much fluid as needed at the time. This reduction in energy consumption lowers the fuel consumption.
For the V6 engine versions, Audi offers a further technology: They roll out of the factory with speed-dependent servotronic steering, which adapts the amount of steering support to the driving speed. When parking, this system provides for easy steering, while at high speeds the support is decreased to ensure maximum precision.
Perfect ground contact: The rear suspension
Guiding, self-steering action, cushioning – the rear suspension in the new Audi A4 has many tasks to fulfill, and it does so magnificently. Its design is based on the toe-controlled trapezoidal layout chosen for the larger model lines, combining compact dimensions with excellent ride quality and comfort. The kinematics, however, were newly developed from the ground up. This also led to the benefit of greatly limited braking sway, thus further enhancing the impression of sporty dynamism.
The backbone of the rear suspension is formed by a torsion-proof and non-flexing subframe, welded together from two longitudinal and two lateral tubes of highstrength steel. This subframe is attached to the bodyshell by four rubber mounts; these are especially firm laterally for dynamic handling, but they are softer in the vertical and longitudinal directions for better ride comfort. All suspension control arms are acoustically decoupled from the axle subframe by means of elastomer bushings.
If sporty handling is to be combined with a high degree of comfort, the unsprung masses must be kept as low as possible. The two trapezoidal links are cast in warm-hardened aluminum, andthe wheel carriers are of chill-cast aluminum. The upper control arms and the track rods are of forged aluminum. The tubular antiroll bar also combines low weight with high rigidity.
The compact design of the trapezoidal-link suspension has notable packaging advantages: the cargo floor in the new Audi A4 Avant is low and flat, with a loadthrough width of exactly one meter. There are only minor differences between the axles in the front-wheel-drive and quattro models, such as the subframes, which for the quattro models have an additional provision for rear-wheel drive. The suspension springs no longer act on the trapezoidal links as on the previous model, but directly on the wheel arms. In this way they can react with more subtlety while being able to extend the spring travel 20 mm (0.79 inches).
Separate spring and shock absorber mountings improve initial response. The suspension bushings use special rubber mixtures that further enhance ride comfort. As an option, Audi also supplies the new A4 with sports suspension. It has firmer springs and shock absorbers and reduces the body’s ride height by 20 mm (0.79 inches).
The joy of driving in a new dimension: Audi drive select
Audi drive select represents a breakthrough in the midsize class, which propels the A4 into new dimensions. The system integrates all technical components that govern the driving experience; using a button in the cockpit, the driver can determine how sportily or comfortably the system should operate.
Audi drive select will be available in one version in the U.S.A., integrating all three systems of engine/transmission mapping, steering, and suspension controls. The engine’s throttle response, the speed-dependent servotronic power assistance and the Tiptronic shift points all can be programmed into three main fields. The ‘comfort’ mode is ideal for relaxed driving on long journeys or over poor road surfaces; ‘auto’ is the most balanced setting and ‘dynamic’ is the tight, firm stage where the chassis of the new A4 can demonstrate its package of power fully.
Changes between the modes are made using two arrow buttons on the center console. All such changes are performed safely and smoothly. The driver can clearly discern them but is not distracted. The driver has a fourth mode available, known as ‘individual.’ Within practical limits, this personal profile can be assembled from a wealth of possible settings. With Audi drive select, the new A4 is up to four cars in one.
Continuous control: The CDC shock absorbers
The Audi drive select is augmented by yet another innovative technology – electronically governed shock absorbers. The central element is a new highperformance control unit. The computer continuously analyzes the signals from 14 sensors, and it calculates the current for the electronically governed shock absorbers at each individual wheel 1000 times per second.
The so-called CDC (continuous damping control) shock absorbers are gas-filled hydraulic shock absorbers whose operation can be varied continuously. An electromagnetically triggered valve regulates the flow of hydraulic fluid between the inner and outer shock-absorber tubes. A smaller flow cross-section makes the damping characteristic firmer, while a larger one makes it softer. Within the mode the driver has selected via Audi drive select, the control unit employs adaptive characteristics, i.e., it adapts to match the driver’s style and the road conditions.
Every single driving situation requires a specific damping force. In order to keep body movements as low as possible, for example, a high damping force is required. When driving over ridges, low forces are needed, so that when accelerating the jolts are felt as little as possible by the passengers. For good ground contact and minimal wheel load fluctuations, a medium level of damping force is required, as the wheel must not be damped too much or too little. The control unit selects the optimal damping force for every driving situation. The CDC shock absorbers are joined with sporty springs, which lower the body by 20 mm (0.79 inches).
A new level of high-tech: Audi dynamic steering
Yet another innovative technology is available in Audi drive select: Audi dynamic steering. With this feature, Audi is opening a new chapter in the history of the automobile. At the heart of the system is a superposition gear that operates with no play and modifies the steering ratio in response to vehicle speed. When cornering at the handling limits, the dynamic steering system stabilizes the A4 by intervening instantly with small steering maneuvers.
The superposition gear consists of a wave gear (also referred to as a “harmonic drive”) integrated into the steering column and powered by an electric motor. Harmonic drives have been used with a great deal of success in the robotics and aerospace industries. A harmonic drive was used for the first time in space in 1971 on Apollo 15. It was part of the single-wheel drive of the lunar rover that explored the surface of the moon. In 1997 the drive traveled to Mars as part of the Pathfinder mission, in which it was part of the “Sojourner” expedition vehicle. The drive also had a role to play when the Hubble space telescope was launched in 1990.
Tested in the proving ground of outer space, the strengths of harmonic drive technology extend to a number of important areas. The system is extremely compact and lightweight with a high level of torsional rigidity. Its lack of play allows it to operate with extremely high precision and very little friction, while transmitting immense torque with a high degree of efficiency. Audi is the very first manufacturer to take all of these brilliant characteristics – that together far exceed the solutions offered by the competition – and apply them to automotive technology.
Audi dynamic steering can vary its steering ratio in response to both the vehicle speed and the Audi drive select mode in use. Transitions are continuous and imperceptible. System involvement is very direct when parking. Drivers can cover the entire steering range in just two turns of the wheel – a maneuver made nearly effortless, thanks to a high level of power assist. At moderate highway speeds, the system becomes less direct and provides less power assist. At top speeds, an indirect steering ratio and low level of power assist make it easy to keep the vehicle in its lane.
Audi A4 seems so classy on its sleek body paint, and it is already very striking on that color but to be honest I don’t like its interior features and even its touch. It looks so boring.
I really love the classy and expensive look of this Audi A4, and I must say that it is already looking great on its color. The figure performance of this is quite impressive either.
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10.26.2011 @ 01:41