IW STi Forum banner
Cancel
Create thread New Garage Forums

Damper tuning and dyno graph discussion

Suspension/Stiffening
Jump to Latest
38K views 65 replies 22 participants last post by  BigSky  
#1 · (Edited)
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/techarticles/shock_absorber_shock_dyno/ (really basic article for newbie's)
http://www.circletrack.com/techarticles/139_0307_shock_absorber_tech/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.
 

Attachments

#2 · (Edited)
Re: Damper tuning and dyno graphs

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.
 

Attachments

#3 · (Edited)
Re: Damper tuning and dyno graphs

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/
 

Attachments

#4 · (Edited)
Re: Damper tuning and dyno graphs

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.
 

Attachments

#5 · (Edited)
Re: Damper tuning and dyno graphs

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.)
 

Attachments

#6 ·
Great thread, thank you very much for the info and graphs... good stuff ! :D
 
Save
Reply Quote Like Like
#7 ·
Re: Damper tuning and dyno graphs

stretch said:
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/
Click to expand...
Hey stretch, which graph is the PSS9?
 
#10 ·
Re: Damper tuning and dyno graphs

lackskill said:
I think the left graph is the PSS9, the middle 2 are KW, and the right is Tokico.
Click to expand...
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.
 
#15 ·
Cool! Thanks a lot stretch! :tup:
 
Save
Reply Quote Like Like
#16 ·
lackskill said:
Currently Active Users Viewing This Thread: 5 (4 members and 1 guests) lackskill, GoodTimes, RaceComp Engineering, stretch

I see you.
Click to expand...
I've read that if a company does not want to (or cannot) share it's dyno graph then it has something to hide and to stay away. If they start talking about proprietary gobbly-****, RUN!! :lol:

I'm interested in the T2 dyno graphs as well. ;)
 
L
#20 ·
KarlSTI said:
I've read that if a company does not want to (or cannot) share it's dyno graph then it has something to hide and to stay away. If they start talking about proprietary gobbly-****, RUN!! :lol:

I'm interested in the T2 dyno graphs as well. ;)
Click to expand...
I was particularly fascinated by his choice of the word(s) (is a hyphenated word 1 word or 2?) gobbly-**** in an otherwise complex technological dissertation.

So how about it RCE?
 
#21 · (Edited)
Thanks guys. So who wants to take all the individual graphs and plot them onto one big high-res uber-chart?

spazegun2213 said:
Someone wants to see a t2 dyno graph, then someone remove a coilover and take it to your nearest race shop. There are two within 20min from me that charge $50 for a shock dyno, and that will tell us for sure.

Its been a long day, and I'll read more of the links tomorrow for sure, thanks strech!
Click to expand...
Aye, that's why I completely don't understand why a company would consider their valving "secret". It's like if Cobb kept the dyno gains from their ECU reflash a secret so nobody could copy the torque curve. I mean, could you image that? The shock dyno curve IS the bragging right of the manufacturer. It's not just RCE; most manufacturers seem to keep this stuff private. It's their choice to do so, but why not brag about it?

I too am cautious about buying products without a dyno. I mean, look at the DMS dyno above. They're a big brand name, expensive, lots of rave reviews, so you'd expect an impressive dyno, right? But the dampers are totally progressive, and that'd be awful for a street car (my purposes). Are they progressive because they're designed for rally cars? I don't know. And Whiteline's then-popular Group-4's, another favorite prospect that a lot of people used to cross-shop, shows almost no digression at any firmness- maybe it's comfortable, but is that really optimal for daily drivers that see track time, too? I doubt it. Still, Kudos to Whiteline for publishing the information so I can make an informed decision- it's given me respect for their company.

One reason I really like Koni is that they usually send the original "test-fit" owner home with a dyno to post online. Koni dyno graphs are usually easy to find. Get one revalved, and you'll get a dyno showing what it's been revalved to. Their valving generally looks to me, at least on paper, to be excellent. (And it usually feels good, too.)

twiSTies said:
so those pss-9's aren't looking too bad now, huh?
Click to expand...
Well, we still don't have an STI-specific dyno of them, just a generic one. It shows more digression than a lot of competing units (all except Zzyzx), diminishing as they're turned softer, which I think is great. If it weren't for the Audi forums dyno, I'd have no reservations about them. Also, it appears as if you keep your Bilsteins at a medium firmness level, then you're valving might not be far off from stock. (Again, though, that's not a car-specific Bilstein dyno, so it may not be even close to representative of the actual product.)

Turninconcepts.com said:
Someone's been busy - great job and research Stretch!!! This is what a technical forum should be about!!
Click to expand...
I see you're playing with some AST coilovers- sounds like you're going to bring back a TIC variant of the Whiteline's discontinued (but popular) kit? I'd be curious if you can get a little more digression in the curve; AST uses some pretty big pistons for their price range, which should allow the necessary piston control if they use the right valves.

Has anyone ever used a 3-way or 4-way damper where high and low speed piston movement can be adjusted independently? I'd love to hear your thoughts on what settings worked and why- where low speed and high speed movement was most commonly felt in real world situations. Is there ever a reason to add more high-speed bump? I would think the less, the better, whereas you take as much low-speed bump as possible for a given ride quality.
 
#24 · (Edited)
RaceComp Engineering said:
Ooooooh.....you guys are pushy :lol::lol:

Myles will be out most of the day, but maybe I can persuade him when he gets back in. We'll see. No promises.


- Andrew
Click to expand...
Well, I talked to Myles- he wanted to talk to me directly to avoid any confusion. Basically, Myles doesn't want to open up their coilovers to undo criticism. (As if that happens on the Internet... ha.) Posting a dyno chart is like opening up a can of worms. Anyway, RaceComp knows their valving works, and Myles doesn't want people to over-analyze what the graph looks like.

That said, I still asked for him to put up the dyno- my interest is in seeing why the T2's work as well as they do. But it's not gonna happen. RaceComp feels they have little-to-nothing to gain by putting it up (except props from a few people reading this thread). Anyway, it was nice to finally talk to the man, the myth, the legend: Myles.
 
#25 ·
stretch said:
Has anyone ever used a 3-way or 4-way damper where high and low speed piston movement can be adjusted independently? I'd love to hear your thoughts on what settings worked and why- where low speed and high speed movement was most commonly felt in real world situations. Is there ever a reason to add more high-speed bump? I would think the less, the better, whereas you take as much low-speed bump as possible for a given ride quality.
Click to expand...
you might want to pose that question on a forum like rennlist, or another higher end racing forum.

oh, and I'm still reading! damn you strech for linking 11ty billion articles!
 
#26 ·
stretch said:
Well, I talked to Myles- he wanted to talk to me directly to avoid any confusion. Basically, Myles doesn't want to open up their coilovers to undo criticism. (As if that happens on the Internet... ha.) Posting a dyno chart is like opening up a can of worms. Anyway, RaceComp's valving works, and Myles doesn't want people to over-analyze what the graph looks like. After all, and I agree with him on this, more of this and less of that on a chart doesn't mean squat next to seat time.

That said, I still asked for him to put up the dyno- my interest is in seeing why the T2's work as well as they do. But it's not gonna happen. RaceComp has little-to-nothing to gain by putting it up (except props from a few people reading this thread), so I guess I understand his position. That doesn't mean I won't stop asking for a dyno though, cause I think seeing the charts are really educational for us car nerds! I just hope Myles doesn't take my (our?) persistence personally.
Click to expand...
uh.....OK.
 
IW STi Forum
posts
4.1M
members
124K
Since
2001
A forum community dedicated to Subaru Impreza and STI owners and enthusiasts. Come join the discussion about performance, engine builds, exhaust, modifications, troubleshooting, maintenance, and more!
Full Forum Listing
Explore Our Forums
GD-General 2.5 Liter/Litre Factory Motor GD-Members' Journals General Subaru Discussions 2015+ STI Discussion