Koni Sport dampers and Evolution driving school..

[kcbrown]

I've re-uploaded the attachments and re-linked them anew. Try it again, please.

 

[sheizasosay]

So I hear 1-5 inches per second is where it's at. Which puts relevant damping at 265ish in/lbs for the "labeled" fronts and 420ish in/lbs for the labeled rears. Soooo backwards....

 

[Norm Peterson]

I've re-uploaded the attachments and re-linked them anew. Try it again, please.

Pictures work (thanks).

Zipfile still insists on being an unopenable *.php file, whatever that is.


Norm

 

[kcbrown]

Pictures work (thanks).

Zipfile still insists on being an unopenable *.php file, whatever that is.


Norm

What browser are you using? You should be able to simply click on the zip file link and have it download. Under Firefox, this seems to work properly. How large is the resulting file you get on your computer? Even if it claims to be a .php file, if it's 1.5 megabytes in size, it means you're getting the file properly and can just rename it to a .zip file and then open it.

 

[Norm Peterson]

Win 8.1, IE 11.

I get the box where I can opt to open, save (or save as), or cancel. Selecting either open or save results in a little box flashing up on the screen that immediately disappears. I have no clue what (if anything) has happened, no idea if anything downloaded, what its name might be, or where in some ridiculous number of GB Windows decided to put it..

Communications/connectivity software is a big mystery to me, and I'm unwilling to make matters worse for myself by loading a second browser and struggling with it and any potential conflicts with IE that at least doesn't bite me in the ass like this too often. Sorry for ranting . . .


Norm

 

[kcbrown]

Win 8.1, IE 11.

I get the box where I can opt to open, save (or save as), or cancel. Selecting either open or save results in a little box flashing up on the screen that immediately disappears. I have no clue what (if anything) has happened, no idea if anything downloaded, what its name might be, or where in some ridiculous number of GB Windows decided to put it..

Select "save as". It should bring up a dialog that asks you what to name the file. When you do that, you'll at least know where it's putting it because the dialog shows what folder it's going into.

Communications/connectivity software is a big mystery to me, and I'm unwilling to make matters worse for myself by loading a second browser and struggling with it and any potential conflicts with IE that at least doesn't bite me in the ass like this too often. Sorry for ranting . . .

No worries on that. We'll figure it out, it's just a matter of getting it to a point where it's doing something obvious.

 

[Norm Peterson]

I think I finally have it . . . and what a PITA just to get a bunch of numbers.

The *.csv files I get, but what are those *.mcr and *.mcr.xml files?


Norm

 

[kcbrown]

I think I finally have it . . . and what a PITA just to get a bunch of numbers.

Heh. Sorry about that. Didn't know of a better way to make that happen in such a way that you could use it in a computer, and it's generally good form to publish the raw data files in the form you originally got it. Since those are in some proprietary binary format, there wasn't much I could do but stick them in a zip file.

The *.csv files I get, but what are those *.mcr and *.mcr.xml files?

The *.mcr files are the original raw files I was given by the dyno shop. You can open them with the Roehrig Engineering software I linked to (indeed, I don't know of anything else that can open those).

The *.mcr.xml files are ones I exported from within the software. Each one should reflect the data in the corresponding *.mcr file. I performed those exports in case someone wanted to see all the data in a (somewhat) human readable form without having to go through the software first, and figured there might be some computer savvy people on this forum that could do something interesting with it.

 

[Kobie]

Math is hard.
Can someone figure out what the position (turns from full soft) 65% is for some of the common springs that are out there?
Such as:
Steeda Sport
Steeda Comp
Ford K
Eibach Pro

 

[kcbrown]

Math is hard.
Can someone figure out what the position (turns from full soft) 65% is for some of the common springs that are out there?
Such as:
Steeda Sport
Steeda Comp
Ford K
Eibach Pro

Sure thing. Just give me the spring rates (front and back) for each and I can compute that.

I just need to know what speed range should I be using to compute the average resistance rate. I can, for instance, use a range from 1 to 4 inches/sec.

 

[Kobie]

Copied from another forum.

Eibach Pro-kit (pn 35101.140) / Ford Racing (K-springs) (pn M-5300-K) 1.5/1.7 - both variable front: 173-248lb/in / rear: 195-236lb/in

Steeda Sport (pn 555-8216) 1.0/1.25 - front: 200lb/in / rear: 175lb/in

Steeda Competition (pn 555-8241) 1.0/1.25 - front: 225lb/in / rear: 185lb/in

 

[kcbrown]

Copied from another forum.

Eibach Pro-kit (pn 35101.140) / Ford Racing (K-springs) (pn M-5300-K) 1.5/1.7 - both variable front: 173-248lb/in / rear: 195-236lb/in

Steeda Sport (pn 555-8216) 1.0/1.25 - front: 200lb/in / rear: 175lb/in

Steeda Competition (pn 555-8241) 1.0/1.25 - front: 225lb/in / rear: 185lb/in

Variable rates are somewhat problematic, as there is no single critical damping value for them (but, rather, a range). It means there may be more than one 65% critical setting.

I'll presume the weights for your car are the same as mine for computing critical damping. It should be reasonably close regardless.

 

[Mineral_'01]

kcbrown,

Thanks for posting that link to the Roehrig Engineering software. Lots of playing around to do now and a steep learning curve to get past using the software. Cool stuff.

Happy Thanksgiving!

 

[Kobie]

kcbrown,

Thanks in advance for doing this! I'm sure it will help a lot of people at least get a starting point when setting their Koni yellows with these combinations.
Happy Turkey Day Everyone!!

 

[kcbrown]

I didn't respond to this before, due to getting caught up in other things. Sorry. Lots of good points in your message, but I especially wanted to respond to this:

Again let me point out I'm not telling you to NOT think about things like you want too. Just don't put so much damned stock into them because it will bog you down. And remember while I don't personally know you, I did get a debrief about how things went in general, including the conversation about how you can't talk while driving and it messes you up, etc.... but then you nailed a slalom while... telling Shelly that. Keep the brain clear. Apply your lessons well and you might find you don't need to think so hard about how things are happening with the car.

Yeah, that took me by quite a bit of surprise. My takeaway from that is that I should just relax, drive the car, enjoy it, learn what I can, and not prejudge my abilities.

I know the stock suspension might not be terribly good for performance driving compared with what it could be, but so far, it's been awfully difficult for me to find something about it that had hindered me. That may be a reflection of where I am as a driver right now, or it may be a reflection of my driving style, or it may even be a reflection of some inability on my part to determine what is holding me back, or maybe even that I'm being held back.

The car with the Konis feels better, with the bulk of that improvement being in the ride itself, how it handles bumps, etc. It also handles transitions (the slalom) at least as well as stock, and almost certainly better. I don't really know because the only way I can really know is to compare two cars or settings back to back under the same conditions at about the same time, and there are several months between my previous Evolution drivings school and this one. The car certainly handled the transitions decently in stock form. I don't have any sense at all as to whether the car did better in the slalom this time compared with before, but at least it didn't feel worse compared with my vague memories of how it performed before.

I do notice that it's easier for it to turn in, because it will now oversteer a bit simply by lifting the throttle, whereas before it would simply rotate (follow the curve with both ends) under those same conditions. I know it oversteers now because I had to countersteer slightly to correct it, something I never had to do the previous time. I attribute that more to the camber plates than the Konis, but I don't really know which of those dominates that particular change.

There's a pattern to my observations to be found in the above. I notice differences in behavior characteristics more than differences in degree, at least when attempting to compare behavior that was observed several months ago with behavior more recently observed (the ride improvement is something I noticed, but then, I'm not relying on memory of months-old experience for my impressions of the stock ride). I suspect that would be true of many, but would expect that people who are very experienced would be better at that because they're more in tune with the subtleties of what the car is doing, and would think that those things would make a greater impression on them, sort of how changes in characteristics make a greater impression on me.


The point of all that is that while many might not regard the stock suspension as even being "OK" for performance driving, if the differences in behavior between the stock suspension and one that is at least "OK" for performance driving result in changes that are only noticeable to someone who is highly experienced (enough that they easily detect subtle differences in behavior), then it follows that it's likely to be insufficient only for such highly experienced people, but perfectly adequate for those with less ability than that. Put another way, adequacy of the suspension probably depends on the ability of the driver more than anything else. I doubt the stock suspension is adequate for performance driving when you or Terry Fair are driving, but what of those who, like myself, can hardly tell the difference between the stock suspension and something better?

I definitely agree that it's not sufficient for competition driving, unless the playing field is held level by specifying the stock suspension.


If I find myself getting to the point where my current setup is inadequate, then I'll take it to the next level. The real question is: how will I be able to tell that it's the car holding me back and not my own driving abilities?

Finally, I should note that I'm not in this to win competitions. I'm in this strictly for the fun of it. Even in its stock form, the car is great for that. The only reasons I changed dampers is that I needed camber plates anyway and knew that the ride could stand improvement. Now that both of those issues have been addressed, I guess it'll come down to whether or not I've stopped having fun with my car. That's unlikely, to say the least. I won't be surprised if I make no other changes to the car. But you never know until you get there!

 

[kcbrown]

So here's the average rebound rate for each damper at each setting. "Pass" here is the same as the number of 1/4 turns past full soft. Location is "f" for front and "r" for rear.

Note that I'm averaging the two rebound curves together (there's hysteresis in these dampers) as well as averaging the left and right sides together, since the idea is to give you some notion of what setting to use for your dampers, and not for my specific ones. It's the best I can do with what I've got.

Without further ado, here's the average rebound rates between 2 and 3 inches/sec shaft velocity (people who don't know SQL can ignore the query, which I put there for completeness). The values are negative because the slope of the rebound curve is negative:

kevin=> select location, pass, avg(rate) as rate
from (select substr(shock, 1, 1) as location, 
pass, avg(forcediff / speeddiff) as rate 
from shockdampingdiffs sdd join shockcurveattributes sca 
using (shock, pass) 
where type = 'rebound' and speed > 2 and speed < 3 
and sample >= first and sample <= last 
and abs(speeddiff) > 0 
group by shock, pass order by shock, pass) t 
group by location, pass order by location, pass;

 location | pass |        rate        
----------+------+-------------------
 f        |    0 | -28.5252852953472
 f        |    1 | -28.7219906633222
 f        |    2 | -29.9974361032989
 f        |    3 | -32.7627499977644
 f        |    4 | -32.2284162702381
 f        |    5 | -34.1830667583725
 f        |    6 | -35.7649128091112
 f        |    7 |  -40.603480414513
 f        |    8 |  -42.288092948718
 f        |    9 | -44.3218941610925
 r        |    0 | -20.9190039082295
 r        |    1 | -23.3490962959941
 r        |    2 | -25.8289492753623
 r        |    3 | -28.8198268077564
 r        |    4 | -32.6267659084575
 r        |    5 | -39.6733845662011
 r        |    6 | -45.7631262193423
 r        |    7 | -53.8557304493514
 r        |    8 | -58.5020354240815
 r        |    9 | -68.3945583427389
(20 rows)

The formula for critical damping in rebound (for compression I'd expect you'd use the unsprung corner weight rather than the sprung weight) is:

CD = 2 * sqrt(SpringRate * SprungCornerWeight / 386.4) / (MotionRatio ^ 2)


Where SpringRate is in lbs/in and SprungCornerWeight is in lbs, and the result (CD) is in lbs/(in/sec), or lbs-sec/in. For the front, the sprung corner weight is 945 lb, and the motion ratio is about 0.97. For the rear, the the sprung corner weight is 747 lb, and in two wheel bump, the motion ratio is 1. Note that these weight values are derived from the curb weight of my car (2014 GT) plus my weight as the driver. It should be reasonably close for most of us.


Here's the critical damping values I get for the springs that were mentioned so far:

[FONT=Courier New][SIZE=1][SIZE=2]Type                       Front Rate     Rear Rate     Front CD    Rear CD
-------------------------------------------------------------------------------
Steeda Sport               200            175           47.0        36.8
Steeda Competition         225            185           49.9        37.8
Ford K Springs             173-248        195-236       43.7-52.4   38.8-42.7[/SIZE]
[/SIZE][/FONT]

So for the Steeda Sport springs, front 65% critical is 30.6, while rear is 23.9, which corresponds to 3/4 turn from full soft up front, and 1/2 turn in the rear (those get you about 70% critical).

For the Steeda Competition springs, front 65% critical is 32.4, while rear is 24.6, which corresponds to 5/4 (i.e. 1 1/4) turn (for 69% critical) and 1/2 turn in the rear (for 68% critical).

For the K springs, it's going to depend on what the actual working rate of the springs is. The front adjustment range target is from 28.4 to 34.0, which is anywhere from 1/4 turn to 5/4 turn. The average gets you 3/4 of a turn. The rear adjustment range target is from 25.2 to 27.8, which is anywhere from 1/2 to 3/4 of a turn. I'd probably leave that at 3/4 of a turn (a value of 28.8) which puts you at 74% critical damping even for the low end.


There's probably enough variability in the actual rates you'd get from your shocks that these settings would be ballpark anyway, but it should be clear that getting sufficient damping to properly control the rebound doesn't take much adjustment above full soft in the general case for these performance springs. Note how the front isn't able to even get to full critical damping for the Steeda springs, at least for the speed range here (2 to 3 inches/sec), and is barely able to get past critical for the softest part of the Ford K springs.

So it looks to be impossible to overdamp these performance springs up front, but relatively easy to achieve good damping. The rear is another matter. There, you may have to be more careful about your settings, as the damper is capable of going up to at least 160% of critical for even the stiffest range of the K springs.


Note that I'm presuming a motion ratio of 1.0 for the rears. That is almost certainly incorrect, but I don't have data on the angle of the dampers, so I can't compute what motion ratio to use back there. Complicating the matter is the fact that the wheel rate from the springs, which I've been presuming to match the spring rate on the basis of a motion ratio of 1.0 in double-wheel bump, probably changes in single-wheel bump. Norm should be able to give us some idea of what motion ratios to use for these various scenarios, and he may even have angle data (and thus motion ratio data) for the rear dampers.

 

[Mineral_'01]

Outstanding! Excellent work. I vote for a sticky of critical damping with various spring rates and Konis here in the corner carving section we can add to in the future. It would be an excellent reference for people wanting a base line with their Koni setup.

Just wish I had some dyno plots and data for the GC konis to compute CD for my setup...

 

[kcbrown]

Outstanding! Excellent work. I vote for a sticky of critical damping with various spring rates and Konis here in the corner carving section we can add to in the future. It would be an excellent reference for people wanting a base line with their Koni setup.

Thanks. Glad I could contribute something here.

Just wish I had some dyno plots and data for the GC konis to compute CD for my setup...

The dyno runs cost me about $20 for each damper. Not bad, really. I highly recommend you get your dampers dynoed if it's not too inconvenient.

Not only will it tell you about what setting to use to get a given fraction of critical, it'll also tell you how much variation there is between the left and right sides. I now have that for mine (and the results show a bit of a difference, particularly in the rear), but the shop didn't make it possible to track the plots back to specific dampers, so I can't account for side to side variation in my settings. Frankly, I don't think that matters for my case, because I don't feel any side to side difference. Someone with a really well-calibrated posterior might be able to, but the difference is small enough that even they might not (could anyone feel a difference of a few percentage points of critical, particularly when it's already up in the 75% range?).


The raw data has made it possible for me to determine that my rear settings are actually a tiny bit too aggressive, putting them at about 80% critical. The front is at around 75%, and there's nothing I can do about that, as I'm only 1/4 turn from full soft. I may drop my rear by 1/8 of a turn to bring it back to around 75% critical, but I rather doubt that doing so would really make much of a difference. The nice thing is that I can experiment with this to my heart's content.

 

[Sam Strano]

Here's the critical damping values I get for the springs that were mentioned so far:

[FONT=Courier New][SIZE=1][SIZE=2]Type                       Front Rate     Rear Rate     Front CD    Rear CD
-------------------------------------------------------------------------------
Steeda Sport               200            175           47.0        36.8
Steeda Competition         225            185           49.9        37.8
Ford K Springs             173-248        195-236       43.7-52.4   38.8-42.7[/SIZE]
[/SIZE][/FONT]

So for the Steeda Sport springs, front 65% critical is 30.6, while rear is 23.9, which corresponds to 3/4 turn from full soft up front, and 1/2 turn in the rear (those get you about 70% critical).

For the Steeda Competition springs, front 65% critical is 32.4, while rear is 24.6, which corresponds to 5/4 (i.e. 1 1/4) turn (for 69% critical) and 1/2 turn in the rear (for 68% critical).

For the K springs, it's going to depend on what the actual working rate of the springs is. The front adjustment range target is from 28.4 to 34.0, which is anywhere from 1/4 turn to 5/4 turn. The average gets you 3/4 of a turn. The rear adjustment range target is from 25.2 to 27.8, which is anywhere from 1/2 to 3/4 of a turn. I'd probably leave that at 3/4 of a turn (a value of 28.8) which puts you at 74% critical damping even for the low end.


There's probably enough variability in the actual rates you'd get from your shocks that these settings would be ballpark anyway, but it should be clear that getting sufficient damping to properly control the rebound doesn't take much adjustment above full soft in the general case for these performance springs. Note how the front isn't able to even get to full critical damping for the Steeda springs, at least for the speed range here (2 to 3 inches/sec), and is barely able to get past critical for the softest part of the Ford K springs.

So it looks to be impossible to overdamp these performance springs up front, but relatively easy to achieve good damping. The rear is another matter. There, you may have to be more careful about your settings, as the damper is capable of going up to at least 160% of critical for even the stiffest range of the K springs.


Note that I'm presuming a motion ratio of 1.0 for the rears. That is almost certainly incorrect, but I don't have data on the angle of the dampers, so I can't compute what motion ratio to use back there. Complicating the matter is the fact that the wheel rate from the springs, which I've been presuming to match the spring rate on the basis of a motion ratio of 1.0 in double-wheel bump, probably changes in single-wheel bump. Norm should be able to give us some idea of what motion ratios to use for these various scenarios, and he may even have angle data (and thus motion ratio data) for the rear dampers.

So, here's what's ironic. Without all those maths, you'll note that I tend to recommend to folks to start out at about 1 turn up in front, 1/2-3/4 turn up in the rear.

From there YOU have to find what works best. And by what works best I mean what feels and acts in a way that is to your liking, for how you use and drive the car. And here's a dirty secret, you can do all the math you want to figure critical damping (which I guess I kind of hit on being stupid <G>), but it doesn't account for any number of other factors in which you might want to adjust the dampers.

Tires all differ in construction and compound. Some turn in better than others. Some are more prone to oversteer on entry, some make the car push more, etc. You also adjust your damping to effect change there. If the numbers could do the job you'd not have racing winning cars on multi-car teams running different setups. You'd not have adjustable shocks, or adjustable anything else for that matter) on a car. But the reality of the situation is such that you need tuning to really dial a car in. And until a computer drives the car, the dynamics of what is happening is much more important than they theoretical.

I get that some of you guys like to push numbers around. That's ok, but know when to say when. And as for not wanting to "win" anything and using that as an excuse, I guess I don't buy it. If that were true then no need to go to schools, or pay to enter autocrosses, etc. The numbers that matter in terms of performance are those on the clock, not on the spreadsheets.

Bottom line, I suppose it's a bit frustrating for me on a personal level for a few reasons. I know that I have busted my ass to figure out what does and doesn't work, and have proven time and time again that I've figured it out better than those that are hung up on numbers. But that's not even the real issue I have. That one is this, and it's part of the title of this thread. I've been teaching for a long time. The most frustrating students are the ones that get into their engineering box. They don't learn as well (if at all), they tend to be argumentative, and very very set in their ways. Open you mind to things you can't quantify to the Nth degree, it's actually not so bad and will make you a better driver.

90% of autocrossers are very technical. Engineers, programmers, accountants, etc. But the number of those folks that are really good at it is far less than that 90% and you start to see folks who can think more abstractly on the fly are going to drive better. The car will in turn react better. And the sum of both is that it's FASTER.

If you are out to do the numbers as a mental exercise that's fine. But you have to trust me when I tell you that it never stays that way and Paralysis by Analysis always sets in when I'm instructing those who can't shut it off when in the car. Also you can learn a lot about what the car likes and wants by not asking it to do something it doesn't like (it'll tell you), and tuning with a basic foundation of how things work. Like for example, typically more rebound at one end of the car makes that end of the car react faster to inputs and roll slower. And that's how I came to know that a basic setting for Koni's on Sports is around 1 and 1/2-3/4 turn... for the street. Autocrossing you typically want MORE than critical damping. And in fact you'll find that most performance cars have more than critical damping in them.

And finally. If the critical damping was the end all be all, you'd not have so many cars with adjustable damping, or MR dampers showing up. But they are because 'critical' isn't always the best driving or feeling.

 

[csamsh]

Paralysis by Analysis...that's a good one. I'm going to have to steal that.