Volvo S80 with active chassis - FOUR-C

Volvo S80 with active chassis - FOUR-C

The Volvo S80, the flagship of Volvo's sedan range, is now available with optional Four-C chassis suspension system. The same type of actively controlled chassis as fitted to the high-performance Volvo S60 R and V70 R. The difference is that in the Volvo S80, this technology has been adapted for front-wheel drive and is exploited primarily to enhance comfort.

As in the S60 R and V70R, the driver has the option of selecting chassis behavior, with a choice between a Comfort and a Sport setting. An Advanced Sport mode is added to the S60 R and V70 R.

Volvo active chassis technology makes for an extremely comfortable ride, particularly on poor quality road surfaces. Damping is adjusted continuously in response to road surface for an almost 'gliding across the road' feel. When the urge strikes to be a bit more spirited on an inviting stretch of twisting country road, a light touch on the FOUR-C button and the chassis setting is immediately transformed to suit a more enthusiastic driving style.

In Sport mode the dampers become firmer for a sportier road feel. This Sport setting gives the car quicker steering response and a firmer grip on the road. With a micro-adjustment time of about 500 times per second for each shock absorber, the suspension system is ready to respond almost instantly to driver and road demands.

In the "Sport" and "Comfort" settings, the Four-C chassis uses the control technology called Sky Hook that makes the body feel like it is floating along over irregularities in the road.

"It's almost as if the body of the car is suspended from above on virtual shock absorbers. Hence the expression Sky Hook", explains Marcus Rothoff, head of Four-C Technology development at Volvo Car Corporation.

Optimum distribution

When taking a curve, damping is controlled so that pressure on the road surface is distributed optimally between the four wheels. Well-balanced road surface contact promotes fast and distinct steering response.

To help provide controlled road holding and stability even at higher speeds, damping increases automatically with road speed. If lateral acceleration increases at the same time, for instance in a curve, this too increases the damping rate.

When the car is heavily laden, the damping rate is increased to reduce the risk of the suspension bottoming out and to maintain the car's ride and road holding characteristics.

During braking and acceleration, the system automatically strives to keep the body level with the road surface, without the dipping at the nose or squatting at the rear.

FOUR-C

The active chassis is based on a highly advanced technology known as FOUR-C (Continuously Controlled Chassis Concept). This system was developed together with Öhlins Racing AB. In FOUR-C, each shock absorber is regulated electronically and entirely individually. Damping is varied continuously with immense speed, from soft to hard in less than one twenty-fifth of a second. The driver does not notice the change.

Body and wheel movements are monitored continuously with the help of a number of sensors in the car. The sensors provide about 500 reading impulses a second, measuring parameters such as:

• The car's speed and acceleration
• Lateral acceleration (when taking a curve)
• The wheels' suspension movements
• The steering wheel's position and how fast it is turned
• The engine's current (calculated) torque
• The degree of braking

Owing to the speed of the FOUR-C system, the car can even handle really difficult "washboard" surfaces without causing the wheels to lose their composure.

FOUR-C is optional on the Volvo S80. The system requires that the car is equipped with DSTC - Dynamic Stability and Traction Control - since the DSTC sensors provide some of the necessary information about the car's behavior.

The combination of FOUR-C and DSTC makes the Volvo S80 a highly competent and extremely comfortable long-distance touring sedan - offering exceptional ride comfort allied to dependable road holding properties.

Improved steering characteristics

Just like the Volvo S60 R, Volvo V70 R and Volvo XC90, the new Volvo S80 is now equipped with a steering gear from ZF of Germany. The result is more direct steering response and enhanced steering precision.

ZF is also supplying the new speed-dependent power steering, which requires lower steering force when parking, yet without affecting steering precision at higher speeds.