Koni special active shocks? Worth something?

https://www.koni.com/en-US/Cars/Products/Performance/Special-Active/

worthy of a road car, sure? How about autocross? I'm not a shock wizard like some of you. So I can't read that shock Dyno graph... learn me?

Or are these too new?

The Koni Special Active is just their latest version of the Koni FSD. Rumor is that they just changed the name because the name "frequency sensitive" didn't really make a whole lot of sense. The latter part of that is true. Special Actives / FSDs are really more like stroke-sensitive, non-adjustable Koni Yellows.

The way they work is that they have a second set of bypass valves in them that open up when the dampers compress or rebound short distances. So when you drive over small roadway imperfections and tiny bumps, the fluid goes through the bypass and the dampers don't really provide much damping force. This makes it feel like you have the dampers set softer than they actually are, making for a more comfortable ride. When you corner hard or hit a big bump, the bypass valve slams shut and they act like a stiffer shock.

The downside is that they are much more sensitive to lowering and spring rate changes than a traditional twin tube damper. If you look at European Porsche and BMW forums, you'll find a lot of people complaining of wallowy, uncontrolled handling after installing lowering springs on their Special Actives or FSDs. If you think about how they work you can kind of tell why: Lowering springs reduce the amount of available stroke and they tend to be stiffer, which reduces the length of each stroke given a certain amount of force. These dampers depend on a certain amount of stroke to start working, so if you install a short, stiff spring, the bypass valves will always be open and they'll basically be stuck in full soft mode all the time.

Unfortunately, because of the double valve arrangement revalving these shocks is devilishly complicated. I'm actually not sure if any authorized Koni rebuilder is revalving these things at all because of how difficult it is to test changes with the FSD valve in place. Also, traditional adjusters don't behave the same way that they would on a regular shock when you pair them with a valve like this. That's why they are all non-adjustable (and probably can't be made adjustable very easily).

TL;DR: Probably not worth it for a (serious) auto-x car.

Edit: Added one qualifier to "auto-x car".

In reply to _ :

No I'm just a slow typer.

We had a thread on these not too long ago. This tech has been along for a while, pretty much every damper manufacturer has a version of it, Koni's system is generally one of the better ones. They are realistically more displacement response than frequency response, though those two are pretty well related as high frequency inputs are almost exclusively small amplitude. They're great on an unmodified street car. Can be good on an autocross car with stock springs, but are definitely a compromise relative to sports. If you've got a street car that you occasionally autocross and want great ride quality without autocross performance being worse than stock, these are probably what you want.

In reply to dps214 :

That's what I'm looking for. ATM I'm not looking to lower or change spring rates, but the stock NC shocks are rubbish from new. It is a 90% street car, that's sees about 8 autocross events a year. The wife also rides along for road trips so I want to keep it civil. It's also the reason I got big sway bars instead of coilovers or a shock/spring combo. 

I have a set on my R56 S, and they absolutely transformed the car.  I love these shocks.  Not sure how they would hold up to track work, but for a street and occasional autocross car, they are an easy button, and certainly easy to live with on the street.  I think someone won a national championship on these in '17 or '18 also.  

I'm the one who started the recent thread. FWIW, I just emailed Koni today to ask about the best option for my lowered 128i - I'll post here if I find out anything pertinent.

I had them on my Mazda3 with otherwise stock suspension and I absolutely loved them. Amazing on back roads, soaked up bumps in eerie fashion. Never autocrossed it but with the stock springs I thought it would have done alright. For a primarily daily driver vehicle, I absolutely recommend them. I just put Bilstein 5100's on my truck, but if Koni ever releases a FSD/SA shock for my F150 I will totally get it. 

We put FSDs on the Saab rescue wagon. They were very controlled and rode well. Would buy again. 

We put them on an E46 BMW 330ci and ran them over 125k miles.  I bought them on the recommendation of a Boston resident and their horrendous roads.  They made the car more composed than the OEM shocks, handled corners nicely, and the blow-off valves soaked up the big bumps.