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E46 (1999 - 2006)
The fourth generation 3 Series (E46 chassis) was introduced in 1999 and set the standard for engineering and performance during it's years of production including being named to Car & Driver's 10 best list every one of those years! ! -- View the E46 Wiki

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  #1  
Old 11-26-2005, 06:43 PM
avalys's Avatar
avalys avalys is offline
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Opinions on Koni FSD shocks?

I'm going to replace my shocks in the spring. I've been on the OEM shocks for the past 60,000 miles, and would like to try something different now that I have to replace them anyway.

I'm looking at the Koni FSD shocks (Frequency-Selective Damping). It's a cool idea - the basic concept is that the shocks are designed to be soft in response to high-frequency inputs, as produced by running over bumps, potholes, expansion joints, and so forth, but stiff in response to low-frequency inputs (like that produced by cornering). This means that they improve handling without sacrificing ride quality. There was a review in Roundel recently that praised them highly. They're the OEM shock for the Gallardo.

I'm wondering if anyone on here has had experience with these shocks, and can offer an opinion on them either way. I'm going to be sticking with the stock springs, as I have no desire to lower the car, and I understand they should still be in good shape - is that correct? I assume the Konis will work fine with them.
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  #2  
Old 11-26-2005, 07:39 PM
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Fast Bob Fast Bob is offline
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My only experience with Konis is with the manually-adjusted-damping variety (on my Saleen Mustang). They were great at controlling body motions (2 shocks front/4 rear), but were nowhere near as compliant as the Bilsteins (gas pressure) that I put on my 530i. I`m not familiar with the Konis you`re describing, but they sound quite similar in performance to the Bilsteins....are they gas pressure?

Regards,
Bob
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  #3  
Old 11-26-2005, 08:01 PM
avalys's Avatar
avalys avalys is offline
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Location: Colorado Springs, CO
 
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Quote:
Originally Posted by Fast Bob
I`m not familiar with the Konis you`re describing, but they sound quite similar in performance to the Bilsteins....are they gas pressure?

Regards,
Bob
No, plain hydraulic.
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  #4  
Old 11-29-2005, 10:29 AM
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brave1heart brave1heart is offline
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Mein Auto: '08 Z4 M Coupe, '01 325i
Quote:
Originally Posted by avalys
I'm going to replace my shocks in the spring. I've been on the OEM shocks for the past 60,000 miles, and would like to try something different now that I have to replace them anyway.

I'm looking at the Koni FSD shocks (Frequency-Selective Damping). It's a cool idea - the basic concept is that the shocks are designed to be soft in response to high-frequency inputs, as produced by running over bumps, potholes, expansion joints, and so forth, but stiff in response to low-frequency inputs (like that produced by cornering). This means that they improve handling without sacrificing ride quality. There was a review in Roundel recently that praised them highly. They're the OEM shock for the Gallardo.

I'm wondering if anyone on here has had experience with these shocks, and can offer an opinion on them either way. I'm going to be sticking with the stock springs, as I have no desire to lower the car, and I understand they should still be in good shape - is that correct? I assume the Konis will work fine with them.
The Koni FSDs are too new and you may not find individual reviews on them. In addition to Roundel, check Grassroots Motorsport - they also had an article on the FSDs. Yes, I think you should be able to use them with the stock springs.
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  #5  
Old 11-29-2005, 10:36 PM
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dynosor dynosor is offline
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Mein Auto: 2003 E46 330i
Very interesting!

The Koni FSD concept looks very sensible: http://www.koni-fsd.com/


The traditional method of achieving good body control but allowing the wheels to follow the road is to make the damping rise steeply with vertical wheel velocity up to about 0.15 m/s and then flatten off to rise at a much lower rate - so called digressive valving is achieved with a relief valve that "blows off" to flow oil more freely from a preset pressure. This arrangement works amazingly well on the standard E46 OEM shocks.

This is a compromise because the shock does not know if the wheel is moving at a given velocity because of undulations in the road or because the vehicle body is resonating up and down, pitching or rolling - it applies the same damping at that velocity, and whatever force is applied to the wheel is applied to the body (by definition).

A key fact in the Koni FSD concept is that wheels tend to move at higher frequencies than the body because of the ratio of masses attached to the same spring. As such, FSD sounds like it has the potential to offer an even better ride than stock with good body control:

The ideal system would apply very little damping to the wheels so they can follow the road without applying disturbing forces to the body. It would also apply significant damping to the body to control it motion due to weight transfer during acceleration, cornering and braking, and especially should the body resonate at its natural frequency.

My only experience with Konis was to have them build me custom rear shocks for my 96 GTi VR6 to my damping specs. Konis tends to build shocks that are a little shy in low speed compression damping - high speed compression damping should always be limited on a street car or you can shock your fillings loose:

A rule of thumb for compression damping would be a max of 0.5 G X the car’s mass at that wheel at 1 m/s, or about 400 lb of damping at 3.3 feet per second for the E46 - most OEMs would use less aggressive compression damping.

To prevent pitching over long bumps on the highway the suspension needs to be phased so that the front and rear move up and down more or less together. This requires lower rate front springs compared to the rear (even with 50/50 weight distribution), and damping that rises more steeply at low speed at the rear, but that is more digressive than at the front.

Such a combination of springs and shocks just happens to also induce more weight transfer at the rear during turn-in – this helps the front tires bite and makes the car’s handling more responsive. Weight transfer is further fine tuned with anti–roll bars, with the rear typically being stiffer than the front to further help reduce understeer.

There are no force values given with the attached Koni FSD graph, but a 2:1 ratio of rebound to compression is typical for street cars on stock springs, and this appears to be the case up to about 0.2 m/s.


If I needed new shocks for my 330i I would be very tempted to try these. I might first call Koni to get more info on the exact damping specs, but they would probably not be very forthcoming with those.

Hope this helps
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Last edited by dynosor; 11-29-2005 at 10:51 PM.
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  #6  
Old 11-30-2005, 10:51 AM
adc adc is offline
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I seem to remember that the Roundel article showed a faster time with the regular sport Konis. The FSDs were close but not quite as fast, but they offered a much better ride. (If I remember the article well).

So it depends what you want from the ride/handling compromise.

BTW dynosor, that was a GREAT explanation of shocks for us mortals, thank you!

adc
03 330 ZHP
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