Has any body calculated the motion ratios for the 5th gen base model? Moreover, does anyone have the wheel rates @ given spring rates? Trying to narrow down my valving, and was curious is someone here had already gone through this. Thanks.

 

Hey hell of a question, I've heard chatter about this but never really researched it. Wanna provide more info.

 

The Motion ratio is the amount of damper movement divided by the amount of wheel movment. Knowing this ratio is helpful in deciding on your shock valving, because it provides an estimate for a shock piston speeds when used with a desired combination of spring rates. You essentially get a measure of the motion ratio by physically measuring the distances between the suspension pickup points at maximum droop, and at minimum ride height; however, you have to obtain these #s on a car w/out wheels, antiroll bars and springs. And, since my car is still together, I was hoping someone may have done this , at some point of their build up, or sus replacement.

 

Yeah I just read some stuff on it and that sounds right. So minimum ride height would obviously be the lowest the coil-over (if equipped) can go.

 

Anyone else?

 

How about you just drop some koni yellows on a good spring and not worry about it.

 

i'm going to try this in road racing./autocross to see if you get more replies

 

I have not done the Prelude specifically but generally most of the Civics and CRX that I have done what basically have the same style suspension all come within a few percentage points of .7:1 shock to wheel. I would expect the Prelude is right about that ballpark as well unless someone had the actual data.

 

Try contacting JF at orijinmotorsports.com. I seem to remember he did quite a bit of calculations on the bb6 suspension and may have the data you are looking for.

 

The motion ratios for G2 tegs would probably be more similar to the Prelude than a Civic. I believe these are the same for G3 tegs as well:

Front: 1.5:1

Rear: 1.35:1

Note: wheel:damper

 

If they're the same for G3 tegs, why would it differ from a Civic's?

 

now, could I just do the following? :

1. Measure distance between shock body and "end" of rod (part that contacts shock body at full compression)

2. Disconnect swaybars and install shocks without springs

3. Let suspension hang at full droop, and then use a jack to compress the suspension all the way until it stops (full drop), while measuring how much suspension travel there was.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by TeamSlowdotOrg &raquo;</TD></TR><TR><TD CLASS="quote">If they're the same for G3 tegs, why would it differ from a Civic's? </TD></TR></TABLE>

Why wouldn't it differ from a Civic's?

If Lee is getting 0.7 for Civics then that's significantly different from the .66667 front and .75 rear motion ratios for a G2.

LX4cyl: yeah, you can do that. You can measure the damper compression based on incremented wheel compression changes. The motion ratio will change a bit (it's not linear) at different stages of compression, but most MRs are an average anyway taken near the middle.

 

The info that i have is that the motion Ratio is .59 for the 5th gen Lude. I got this off Preludeonline.com

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by GSpeedR &raquo;</TD></TR><TR><TD CLASS="quote">
If Lee is getting 0.7 for Civics then that's significantly different from the .66667 front and .75 rear motion ratios for a G2.
</TD></TR></TABLE>

No, really it isn't that different. "within a few percentage points of .7:1" is pretty close. Seems like when I did it several years ago it came out about .72 and .68 or something like that so generally .70 all around was plenty fine in the ballpark. Those numbers are close enough to get you in the ball park because you really aren't going to do and use calculations to get to an end valving range where a few percentages point on that are going to mean a hill of beans.

You can certainly use numbers to calculate critical damping but in actuality you don't want critical damping (not if you want good grip or a car that you can stand to ride in). This is a car on an imperfect road or track with people in it an not and engineering class quiz question. Any decent valving, especially if it is adjustable, is more than going to cover your needs. The important thing is to know if the motion ratio is closer to 1:1, .75:1, .5:1, etc. rather than fuss over a few percent that will mean nothing in the long run. Too many variable to split hairs on one thing then calculate in other things with lots of variables, various tolerances, potential measuring inaccuracies, etc.

 

Thanks for the help, Lee. I 'm with you, approximations work for me; as long as I have a watermark, I can go from there.

 

The Prelude is an extremely rarely raced car, so I doubt very much you will be able to find out the answer from someone else. At least I couldn't when I was looking for it. I had calculated once with a formula from Puhn's book, which I'm not sure is very accurate. The equation is spring stiffness/mechanical advantage^2.

I measured the length of the spring with the car on the ground (not the easiest thing with the tire in the way), then jacked up the car 1 inch. Then I measured the spring again. Then I divided the 1" by the change in spring length. That gave me the mech. adv.

You need to know the spring rates on your car (in my case I'm still stock, so I needed a whole 'nother calculation to figure that out), then you can do the same. However, I don't think the equation from Puhn's book gives the mechanical advantage over the whole range of motion.

 

back from the dead.

I just measured it on my 5th gen for future reference. (wheel:damper)

Font 1.56:1
Rear 1.30:1