[stretch]

Professional race car driver Jeff Altenburg once said, "Good shocks are probably the second most significant handling change you can make to a stock car, tires with an alignment being the most significant."

Unfortunately, picking out a good damper is almost never a self-informed decision. Without a dyno graph, you don't know what you're getting at all- and such graphs are hard to come by. Twin-tube, monotube, high-pressure gas, 32-step adjustability- for the most part, these terms are just marketing hype and should be ignored. No, really, even adjustability is just marketing hype until you can verify how it's implemented. Some adjustability is non-existent, and others work in a way that would just decrease overall performance. Seriously.

So, I thought I'd start a thread where we could compile together a bunch of strut dynos and compare them. Since it's hard to translate what feel the driver wants into a graph (unless you're an expert damper tuner, which I'm certainly not), I'm not sure if this thread will actually lead to any useful conclusions. To help out in this regard, here's an excellent article from Grassroots Motorsports that explains what to look for in a damper:

http://www.se-r.net/suspension/shock_tech.html

If you aren't familiar with shock dynos or shock tuning, or just want a refresher on why they're so important, I'd highly recommend giving that article a read. Here are some other good reads, in no particular order:

http://www.circletrack.com/techartic...er_shock_dyno/ (really basic article for newbie's)
http://www.circletrack.com/techartic...ech/index.html (bigger article)
http://www.ozebiz.com.au/racetech/theory/shocktune.html (getting more technical)
http://www.wincom.net/trog/autocross_secrets6.html (opinion piece)

I basically grabbed every Impreza shock dyno I could find. Be warned, some of the graphs show bump resistance on top, others show rebound resistance up top. Some are in metric, some are in imperial. And the scale of the graphs vary greatly, some only dyno up to 5/in second and others much more. I had planned to take all this information and plot it all on one graph, so that all the dynos could be compared on the same scale and units, but I haven't found the time. Perhaps someone else is willing?

To start this discussion, here's a graph I found on Nasioc. I don't know the source (and thus can't verify it's accuracy), but it's been reposted a few times there.

[stretch]

These dyno graphs are courtesy of Whiteline. The now-discontinued Group-4 Circuit Spec coilovers were very popular around here, whereas the available Race Spec coilovers were much stiffer offering. These coilovers are non-inverted monotubes with large pistons, manufactured by the European company AST. Whiteline discontinued them after deciding they were too expensive to manufacture.

You can see the stock STI strut valving matches the Group-4 Circuit valving pretty closely in the rear and the Race valving up front (on full soft). In both cases, the stock STI damper shows slightly more digression in its rebound. Overall, I'd say the valving looks darn close. It's amazing how similar the graphs are yet how differently the owners say they felt! So why do the Whiteline coilovers ride better? My guess is suspension travel: the Whitelines had much more of it.

Circuit Spec: 280lb/in front, 240lb/in rear
Race Spec: 504lb/in front, 448lb/in rear

Here we see the Whitelines v. stock front, then rear, then Whiteline Circuit v. Race, and finally, the STI dampers versus the Evo8 dampers.

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Here are some generic dyno graphs from various manufacturers. These graphs are NOT specific to the STI. Bilstein and KW valve their struts specific to the application they're made for, so these graphs are not going to be representative of an STI-specific strut. However, these graphs are still useful for showing trends.

You can see that Bilstein (first pic) adjusts bump and rebound simultaneously on their PSS-9 monotube coilover system. So does Tokico in their twin-tube D-specs (last pic), but Bilstein shows much more digression in what is likely more sophisticated valving. KW adjusts both independently in their twin-tube Variant 3 coilovers (middle two pics), but only adjust low-speed bump (the digression of the curve). Short of a three-way damper where high-speed damping can be adjusted independently too, is this beneficial to being able to adjust the entire curve?

Koni has some graphs comparing their product to many other popular inexpensive struts, and I won't bother reposting them into this thread (there's a lot). Definitely check these out:
http://www.koni-na.com/presentations/mustang/
http://www.koni-na.com/presentations/civic/

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Here are some Koni dynos. These are the Koni Sports (aka Koni Yellow's, aka Koni SA's, aka Koni 8610's) for the WRX compared to the stock WRX dampers. These fit a 2004 STI or only the rear in 2005+ STI's and are a high-end twin-tube design.

The next graph here is from the Zzyzx coilovers, a $4000 coilover system based on a double-adjustable version of the Koni Sports.

Lastly, we have Ground Control's SA coilover kit (GC also sells the double-adjustables Zzyzx uses), front and rear. These units are custom revalved for Ground Control according to their specs.

[stretch]

These aren't very high-res, but here are some dyno plots from a magazine comparing the 2004 WRX and STI struts to the Tein Flex's they replaced them with. Tein Flex's are really firm and digressive; they'd probably do well on a smooth road course.

However, this guy says Teins are inconsistent and should be avoided. (And on a personal note, I've used Tein basics before and the valving was horrible.)

[AndrewSS]

Great thread, thank you very much for the info and graphs... good stuff !

[Splash]

Originally Posted by stretch

Here are some generic dyno graphs from various manufacturers.

You can see that Bilstein adjusts bump and rebound simultaneously on their PSS-9 monotube coilover system. So does Tokico in their twin-tube D-specs, but Bilstein shows much more digression in what is likely more sophisticated valving. KW adjusts both independently in their twin-tube Variant 3 coilovers, but only adjust low-speed bump (the digression of the curve). Short of a three-way damper where high-speed damping can be adjusted independently too, is this beneficial to being able to adjust the entire curve?

Koni has some graphs comparing their product to many other popular inexpensive struts, and I won't bother reposting them into this thread (there's a lot):
http://www.koni-na.com/presentations/civic/
http://www.koni-na.com/presentations/mustang/

Hey stretch, which graph is the PSS9?

[lackskill]

Originally Posted by Splash

Hey stretch, which graph is the PSS9?

I think the left graph is the PSS9, the middle 2 are KW, and the right is Tokico.

[lackskill]

Once again stretch provides us with a thread that will waste a good 10 hours of work time for me to read.

Thanks stretch!

[stretch]

Originally Posted by lackskill

I think the left graph is the PSS9, the middle 2 are KW, and the right is Tokico.

Aye, that's correct.

To add to that, here's a controversial PSS9 dyno from the Audi forums:
http://forums.audiworld.com/suspension/msgs/1121.phtml

Different car, different damper, though, so take the comments there with a grain of salt.

[lackskill]

Originally Posted by stretch

Aye, that's correct.

Not bad for a Swag...

[stretch]

RaceComp, I keep seeing you view this thread. You KNOW you want to contribute an RCE T2 dyno graph!

[lackskill]

Currently Active Users Viewing This Thread: 5 (4 members and 1 guests) lackskill, GoodTimes, RaceComp Engineering, stretch

I see you.

[RdRacer301]

Great thread indeed.

[Rac10000]

Cool! Thanks a lot stretch!