KONI

FSD

Technical details

FSD is the abbreviation of Frequency Selective Damping. It is the latest technology of KONI, specifically designed to combine the ultimate in comfort and road-holding.

When the emphasis of a car's performance is on the best possible road-holding, a lack in ride comfort is an automatic consequence when using conventional shock absorbers. Not so with the KONI FSD technology!

The groundbreaking FSD technology has been designed and patented by KONI to end the compromise between comfort and road-holding. This new feature can be used as an integrated part of the hydraulic valving system inside the damper.

Consequently no additional cables, sensors, or any other electronic devices are needed to operate this system.

It operates fully hydraulically and is frequency selective and is therefore an economical and effective solution to improving a car's handling. It will give Ride and Handling Engineers a constructive, additional variable in fine-tuning the car's behaviour.

Basically, comfort and handling can be split in two different frequency areas:

• For comfort, with the suspension moving in a high frequency area (± 10 Hz), asking for low damping forces.
• For handling, with the suspension moving in a low frequency area (± 1 Hz), asking for high damping forces.

If you are able to change the damping force level in relation to the frequency of the movement, you create the possibility to solve the conflict in terms of comfort and handling ever present in conventional dampers.

The KONI FSD technology does just that!

Technical details

The graph on the left shows the different frequency areas (click for an enlargement).

Area (1), is what we call the natural frequency of the body, which is around 1 Hz. The roll and pitch movements of the body are in this frequency area and can be reduced by adding more rebound damping.

Area (2), is the natural frequency of the axle, which is around 10 Hz. Although the suspension does need adequate damping in this area not to loose grip, you should also enable the wheels to freely follow the bumps in the road to reduce body motion. At 10Hz the dampers therefore need to be softer than at 1 Hz to keep an acceptable comfort level. Conventional type dampers cannot offer this feature, as damping forces remain unchanged irrespective of frequency, however KONI FSD can!

Areas (3), are all frequencies between 1 and 10Hz. In these areas the amplitudes should be least damped to avoid passenger discomfort. Conventional dampers can cause vibrations in these amplitudes.

The characteristic on the left shows the difference in damping level of a KONI shock absorber with FSD, at the same damping speeds, but different frequencies.

KONI’s new FSD technology: how does it work?

In standard shock absorbers the main damping characteristic is defined by the oil flow going through the piston assembly (1).

Combining it with the FSD feature (2), KONI added a special valve, which controls an oil flow parallel to the one going through the piston rod (3). This parallel oil flow is closed by the FSD feature, giving a rise in damping force almost linear to the time that the piston is moving in one direction.

Put simply: the FSD feature is a hydraulic amplifier that delays the build up of pressure. One could say that an extra tuning option has been created in order to get the best possible combination of handling and comfort.

Since it is an integrated part of the hydraulic valve system inside the damper, no additional cables, sensors or any other electronic devices are needed to operate an FSD damper.

FSD is the simplest and most economic way to significantly improve the ride and driving characteristics of every car. Certainly in comparison with costly systems which work on the basis of computer technology, complex electronics and sensors.