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KONI FSD Dampers Improve Handling Without the Traditional Sacrifice in Ride Quality

Suspension components tested:
BMW Original Equipment Springs, Struts/Shocks & Anti-Roll Bars
KONI Sport "Full Soft" Struts/Shocks (w/ BMW O.E. Springs & Anti-Roll Bars)
KONI FSD (Frequency Selective Damping) Struts/ Shocks (w/ BMW O.E. Springs & Anti-Roll Bars)

Vehicles used:
2004 BMW E46 330Ci Coupe

Original Equipment shocks or struts supplied on new cars from the factory are designed with the inevitable compromise among handling, ride comfort and cost. Tune them for optimum handling, and ride quality usually suffers. Focus solely on comfort, and suddenly your car handles more like your parent’s old 70s Buick than the modern sports car you enjoy driving along the twisty back roads on your way home from work. For many applications, you can find aftermarket dampers that focus more on one of these two priorities, but there is still some trade-off in one area to get more of the other.

Properly called dampers in Europe, shocks and struts work to control the travel of the suspension as a way to smooth the ride and aid vehicle handling. The design of all modern dampers allows them to automatically “self-adjust” or respond to different road surfaces and driving conditions by reacting to the speed of the damper as it moves in and out. Spring-loaded internal valves open or close to adjust the amount of dampening force as the damper moves, which in turn controls suspension movements. Some units also feature user-adjustable settings (from basic manual knobs to sophisticated, electronically-controlled units), allowing the driver to adjust the amount of damping control in an effort to tune ride comfort or handling to their level of personal preference.

KONI engineers have been working on a solution that avoids the normal compromises existing between ride comfort and road handling, with their unique Frequency Selective Damping (FSD) shocks and struts. KONI’s testing has found that the damper movement rate (frequency) that impacts subjective ride comfort is different than the frequency range that affects vehicle handling. Directly related to frequency is the pressure that builds inside the damper as the piston moves through the oil used to produce the resistance needed to control the suspension. By using a special secondary valve that registers the different pressures associated with different frequencies, the FSD dampers can exert the high force needed at low frequencies to control body roll while becoming more compliant for improved ride quality when experiencing higher frequency bumps in the road.

All of this is achieved with mechanical valve systems inside the FSD damper. This engineering solution eliminates the need for elaborate electronic control units, and simplifies retrofitting this system in place of conventional O.E. dampers. Since it is an integrated part of the valve system inside the damper, no additional cables, sensors or any other electronic devices are needed for the FSD damper to do its job.

To get a better understanding of the impact KONI FSD dampers have on a vehicle’s ride quality and handling, Tire Rack team conducted a Real World Road Ride and Performance Track Drive with three of our 2004 BMW 330Ci Coupes. All three vehicles retained the factory BMW suspension components (with approx. 20,000 miles of use), and we left one vehicle equipped with the used O.E. dampers. On the second vehicle we replaced the O.E. dampers with new KONI Sport adjustable dampers, left in their softest setting (as they come in the box from KONI). KONI Sport dampers have long been the benchmark damper for enthusiasts wishing to tune the handling of their car. The third 330Ci was equipped with new KONI FSD units in place of the O.E. dampers.

To keep the variable to just dampers, all three cars were fitted with 225/45R17 Goodyear Eagle F1 GS-D3 Max Performance Summer tires mounted on 17x8.0 wheels, and adjusted to the same cold inflation pressure. In addition to being a popular aftermarket fitment on the BMW 330Ci, the blend of ride quality and cornering traction of the Goodyear Eagle F1 GS-D3 would serve as a good base on which to evaluate the road comfort and handling of the various suspension components.

What We Learned on the Road

Our 5.6-mile loop of expressway, state highway and county roads provides a great variety of road conditions that include city and highway speeds, smooth and coarse concrete, as well as new and patched asphalt. This route allows our team to experience noise comfort, ride quality and everyday handling, just as you would during your drive to school or work.

Our experiences driving the vehicle with the BMW O.E. dampers, shows us just how well sorted and finely-tuned the O.E. suspension seems. The ride over bumps and expansion joints is taut, but not objectionable. Only the bigger hits begin to feel harsh, with a bit of shudder felt through the car in the moment after hitting the bump. Steering response is also good. Without anything else to compare it to, the O.E. suspension feels fine for most situations, sporty and reasonably comfortable on all but the worst road surfaces.

Getting behind the wheel of the car equipped with the KONI Sport dampers, differences were felt immediately. This car feels taut, and more hunkered down to the road, while steering response was improved versus the O.E. dampers, too. Small ripples in the surface of what was thought to be a smooth asphalt road could now be felt. The slap of expansion joints was somewhat more apparent than in the O.E.-equipped car, as was the initial thump of larger impacts. When driving over larger bumps, the car with the KONI Sport dampers did feel more controlled, without the lingering shudder felt with the O.E. dampers after encountering the same bump. This vehicle feels more alive, but also firmer than the O.E. combination, bringing with it the very traditional feel of a sport suspension.

The car with the FSD dampers provided an interesting paradox. Handling felt nearly as lively as in the vehicle equipped with the KONI Sport dampers, while overall ride quality was better than with the O.E. dampers. Steering feedback and response was better than with the O.E. dampers, but not quite as laser-sharp as with the Sport units. When driving over expansion joints and smaller bumps the intrusion was distant enough to be largely forgotten, with only the larger impacts feeling significant but controlled. Our evaluation route contains a fast, sweeping on-ramp with patched and broken concrete. All three vehicles easily held the curve, but with some amount of jouncing and kickback through the steering wheel. The FSD-equipped car carved its way around, without being upset by the bumpy surface.

What We Learned on the Test Track

Our 1/3-mile per lap test track course includes 90-degree street corners, lane changes and simulated expressway ramps. The test track allows our team to experience the traction, responsiveness, handling and drivability normally only encountered during abrupt emergency avoidance maneuvers or competition events. For this evaluation, all track driving was conducted in the dry.

The feel of the BMW with the O.E. dampers on sticky tires like the Goodyear Eagle F1 GS-D3 is well known to our team. Familiarity brings some confidence to press for maximum possible speed around the course. This vehicle felt comfortable and predictable, with some gentle understeer around the steady-state skidpad portion of the course, or as you accelerate past the apex of the 90-degree corners. Jump back to the gas too hard too soon, and more significant understeer sets in, requiring a lift off the throttle and limiting corner exit speed. Smooth, deliberate inputs are needed to lap the course quickly.

To maintain the direct comparison to the road portion of the evaluation, we left the KONI Sport dampers set to the full-soft position. Just like on the road, this car feels hunkered down on the track. Steering response is quicker, and this car transitions more immediately than with the O.E. dampers. The gentle understeer of the O.E.-equipped car is gone, too, replaced with just a hint of power on oversteer in the fast sweeper. The lack of understeer quickly builds driver confidence in this combination, encouraging you to press harder with each corner. The vehicle with the KONI Sport dampers required smaller corrections to steering and throttle to fine tune placement of the car, making it easier to hold a tight line around the skidpad at the top of the course. Some inside rear wheel spin was noticed when accelerating hard around the first turn into the slalom portion of the course, as if the rear shocks were taking weight off the inside tire by holding it up in the air slightly.

The third car, equipped with the KONI FSD dampers, delivered nice overall balance feeling more sure-footed than the car with the O.E. dampers. The FSD car did feel just a bit less connected in the rapid transitions than the car with the Sport dampers, however. But to its credit, the FSD combination did not have the understeer of the O.E.-equipped car, nor the oversteer and inside wheel spin of the car with the Sport dampers. In our evaluation the average lap time for the FSD-equipped car was virtually the same as the car with the KONI Sport dampers. The test track is very smooth asphalt, and we expect if we were testing on a bumpier track, the advantage for the FSD dampers would become more apparent. Given how comfortable this car was on the road, it handles much better on the track than conventional thinking would suggest.

Conclusion

The factory BMW 3-Series suspension is well engineered and finely tuned for everyday use. KONI Sport dampers do a good job livening up the vehicle’s handling, with the traditional feel of a sports suspension (handling versus ride quality). The user-adjustable design of the KONI Sport dampers does allow for fine tuning the ride or handling to your specific preference, and also provides some suspension tuning flexibility for the weekend autocross or track day event. But if you are not going to the track regularly, the KONI FSD dampers may just provide the improvement to road handling you want while also smoothing out many of those bumps along the way.

Product Details

O.E. BMW Dampers: BMW factory-installed struts in front and shocks in the rear, with no user-adjustment capability. Approximately 20,000 miles of use means they are not new, but are also far from worn out.

KONI Sport Dampers – Full Soft Setting: The traditional yellow Sport dampers allow the user to adjust the rebound setting to their personal liking. KONI Sport shock absorbers were developed for sporting drivers by focusing on exceptional road holding and handling properties, combined with an acceptable level of comfort. For this test, both front and rear dampers were left in the softest setting. Read more.

KONI FSD Frequency Selective Damping: Most shock absorbers are designed to offer improved handling through a firmer ride OR to maximize ride comfort. And complete computerized systems can deliver both comfort and performance, but at too high a price for the average consumer's vehicle.

The KONI FSD shock combines excellent road holding and handing characteristics with high comfort levels. Firmness for sporty driving on even road surfaces. Smoothness for a comfortable ride on uneven road surfaces. It's possible via KONI's patented Frequency Selective Damping technology — technology that actively controls the damping level on the basis of the vehicle's body and suspension movement frequency. Read more.


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