Car weight with driver- 2750
front spring- 900



C= .65x2xSQRT(900x((2750/4)/386.09)
C= .65x2xSQRT(900/1.7806729)
C= .65x2xSQRT(505.4269091)
C= .65x2x22.4817

C= 29.2262

So I came up with a number of 29.2262 if the car weights 2750LBS with me in it and saying all corners are perfectly balanced. I used .65 ad zeta because I want to know the damping rate thats 65% critical dampened. How do I convert that number onto a graph? Is it just saying that for every 1in/sec you add 29.2262 on top of the pervious? For example...

1 in/sec 29.2262
2 in/sec 58.4524
3 in/sec 87.6786
and so on...

If this is right you just made my freakin day! please verify my findings before I jump to any conclusions. Do I just do the same math for the rear?

Thanks Man,
Josh

 

Josh-

If the motion ratio was 1, you'd be right (assuming you used a calculator right, I'm just looking at what you plugged in). However, it's not. This is actually the part that tripped me up and is why I couldn't immediately reply to you.

I'm in a hotel in detroit, so I can't confer with my trusty Milliken, but here's how I think it should work. If I'm wrong someone please say so:

You have to calculate the damping at the wheels, not at the shock itself (similar to how with spring rates you're concerned with wheel rates as opposed to spring rates). So spring rate as well as damper displacement need to be converted from displacement/rate at the wheel to displacement/rate at the spring. To compensate for spring rate you use wheel rate instead of spring rate. To compensate for damper displacement you take the critical damping number you get and divide it by motion ratio squared.

So basically, use wheel rate instead of spring rate and also divide the number you get at the end by motion ratio squared, but other than that it's the same. So:

C= (1/MR^2) * zeta * 2 * sqrt(k*MR^2*weight/386.1)

If you wanted you could simplify it with algebra as follows:
C= (2/MR) * zeta * sqrt(k*weight/386.1)

C will be in lb/in/sec, MR should be a fraction (in our case I think 0.7 and 0.67), weight is the corner weight of the car (so for example 2600/4 = 650 lbs) in lbs, spring rate in lbs/in. Also by the way the unsprung weight really shouldn't be factored in here so you might want to take a few lbs (50-ish?) off each corner weight to take that into account.

I plugged in 650 lbs, 0.65, MR=0.7, k=900, and I got damping as 72 lbs/in/sec. Just multiply this by your in/sec and you'll get a force, so at 1 in/sec it'll be 72 lbs, at 2 it'll be 144, etc. This is the front. These are shock forces so they compare directly with a shock dyno chart. Do the same for the rear with the appropriate motion ratio, spring rates, and weights (you might want to bias weight slightly forwards).

Again this is pretty basic - from here people usually tweak it a bit.

Let me know if anyone sees a mistake in there.

 

The kooks definitely grip well past 120 runs. Most agree that they fall off a little bit before cording but I don't think you're near that yet. I've got probably near that many runs on mine and I'm not even thinking about replacing them yet.

Some people had tried the 245 kook and found it's basically very similar to the 255. I haven't personally.

See you in Toledo!

 

Ah yes, forgot the MR included in the equation....thanks integraR0064.

 

Depends how much investigating you want to do. Last year when I was threatened with a protest for flashing my car (for local STR events) and unlocking the device from the car for the NTs. I opened a thread in the Hondata forums and asked this question. Their answer was that any flash changes from the flash pro would change an ecu id # or something similar to this and any scanner that can read the 06+ ecus should be able to identify. I forwarded this to the other B-Stock competitors who questioned me at the time. This is probably why the ecus at were tested in impound last year. After experimenting with this last season, I can tell when v-tec kicks in early or if an AP2 get higher revs. Kinda wish I kept my flash pro after driving Jon's CR at Blytheville. Just as James described, it's hard to believe a flashed/tuned AP2 is the same car/motor. I will still argue that it doesn't increase you run times. Jon's was way too powerful for the grip level.


-marc

 

Marc, from what I remember the flashed CR you drove at the event was running 0 toe in the rear. This would make it very difficult to put the power down. However, in the tuned cars i have ridden in, rear grip was no more of an issue then in any other ap2.

I have been playing around with Jason Rhoades comparative vehicle dynamics thrust calculations and it has really gone to show me how big the tune is for the car.

 

Will damping at the wheel directly correlate to damping on a shock dyno? For example when they graph my shock on a shock dyno my force vs. velocity points arn't taking into consideration I'm going to calculate my critical damping at the wheels. The graph is calculating it at the shock. Right?

So granted it's usesful to know the damping at the wheel, from my thoughts these data points can't be overlayed on my shock dyno sheet. Therefore to look at 65% damping as a overlay on my shock dyno I need to use a formula that calculates the damping force at the shock and not the one that takes into account damping at the wheel? Which is what the formula Nmrado gave me? Or is there a quick and easy way to translate my shock dyno sheet's numbers (if they are at the shock) into wheel damping numbers? Either way would work I would think.

This is my last question refering to this I promise.

Thanks for all the help guys. I just wanna make sure I'm doing this right. Theres a big difference between 1 in/sec equaling 29.22 and 1 in/sec equaling 72.


edit- Looking at my excel sheet to convert spring rate to wheel rate I times the spring rate by MR^2. For example 900x(.7^2)=441 lb/in. So if we take your math equaling 72 lb/in/sec I can work backwards and convert wheel rate to rate at the spring using Z/(MR^2) ex. 441/(.7^2)=900.

If I use this to calc 65% critical damping at the shock It would be 72/(.7^2)= 146.938 lb/in/sec. Using this I can directly correlate with my shock dyno numbers, right?


If your in detroit you should go to that American Jewelry pawn shop thats on TV.

 

Josh - That's why I did all that, was to get it to translate to a shock dyno sheet. The forces occur at the wheel, not directly on the shock, so everything has to be converted so it's at the shock. The first formula you used was incorrect because the car does not have a 1:1 motion ratio.

If you follow the method I gave it outputs a force and displacement at the shock, which is what is on a shock dyno sheet. Which is what you're looking for.

Edit: The part you quoted was written badly, I can see how you thought I was saying how to calculate at the wheels. What I was trying to say was you have to compensate for the fact that the forces are at the wheels.

 

Ok ignore my edit to my post then with some random math at the bottom. Thanks for your help Jon I really appreciate it.

Just found out, my car on setting 8/14 is only 48% critical damping. To bad SRP didn't give me more then one shock settings data point. FML.

 

Hey guys, the club is for us, by us. If you want to be able to fully tune your none 06+ S2000 you should just write a letter (email) asking for a proposal like James's or less specific. If enough people have the "me" attitude about a particular subject, it becomes less "me" and more "we"

Seems to me that the current proposal doesn't go far enough for parity for all S2000s despite the fact that they are so similar otherwise.

www.sebscca.com