By Staff Writer
Sep 1, 2023
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Koni Special Active
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Photography Credit: David S. Wallens
Do you have to sacrifice ride comfort for handling when it comes to dampers? Not so, according to Koni.
Koni Special Active dampers can do both thanks to its patented Frequency Selective Damping (FSD) technology. Plus, the dampers achieve this mechanically without the complexity–and expense–of an electronically controlled suspension.
To understand what a damper does as you ride down the road, let’s break it down to its basic functions.
It moves in (aka compression) and out (aka rebound) and then repeats as the absorber moves to follow the road’s surface. The number of times it completes that cycle (aka stroke) per second determines its operating frequency (measured in hertz, Hz).
Within the body of the damper is a piston that moves through oil to control or damp the movement. The resistance of that piston to move in that environment is its force. The design of that piston and surrounding peripherals, aka valving, determine that force.
Generally speaking, road irregularities and sharp, short duration bumps (think seams on a concrete highway) cause high frequency energies (7 Hz or more) that can be harsh and uncomfortable or cause tire grip issues. Lower instantaneous damping forces will improve the ride comfort and grip.
However, longer duration road inputs and suspension movements (think body roll transitions through a smooth surface corner or an autocross slalom) cause low frequencies (2 Hz or less) where more damping control is desired and ride harshness is not a concern. Having higher damping forces will improve the handling.
On real-world roads, these situations and energies are not isolated but are mixed together and happen all the time. A damper with frequency sensing capability, such as Koni Special Actives, can filter out high frequency harshness while better controlling low frequency body motions. A damper that is unable to distinguish different frequencies will be compromised with more harshness and generally less body motion control.
So, how do Koni Special Active dampers respond to both speed and frequency? Is there a computer? A little guy inside? Dark magic? None of the above.
It does so mechanically.
Exclusively.
The Koni Special Active has a secondary valve system, with a bypass valve and reservoir, that controls an oil flow parallel to the main one.
When the damper experiences fast frequencies, the reservoir doesn’t have time to fill up with oil before the damper moves into compression. The bypass valve remains open and thus the damper applies less of the rebound force that negatively impacts ride quality.
When the damper experiences slower frequencies, the bypass valve closes, moving all that damping oil flow through the smaller openings in the main piston, increasing rebound force and controlling body movement.
A small valve at the bottom of the shaft can be used to tune the rebound damping. This helps the system as a whole by providing a better balance of road comfort and handling than conventional dampers.
Koni offers the Special Active for a wide variety of applications, from trucks to cars to SUVs. Special Actives offer an additional benefit for one particular application.
If you have a convertible, roadster or other open-top vehicle, you might have experienced “cowl shake.” This phenomenon is when the dashboard vibrates from the irregularities of the road. The lack of chassis rigidity in an open-top car often causes this.
The FSD technology in the Special Actives helps minimize cowl shake. This is why Koni made Special Actives for Mazda Miatas and the company looks to offer more products for other convertibles in the future.
As far as what it's like to ride on Koni Special Actives, let’s go back to when our sister publication, Grassroots Motorsports, first tried them. Here were their driving impressions:
We tested the Koni FSD shock absorber on a BMW 330Ci at Tire Rack’s facility and on the craptacular roads that surround South Bend, Indiana. When compared to the BMW OE shock absorber, the difference was quite noticeable. The car felt softer, quieter and more comfortable over bumps while also being much more composed under quicker transitions.
To find out what Koni offers for your ride, visit shop.koni-na.com.
Not only can you find which Koni products fit your vehicle, but you can also purchase a set of dampers directly from Koni and have them shipped to you.
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