DC2R Ride Motion Ratio

[ewendc2r]

Hi,

Long shot but has anyone measured / researched / found out the Ride Motion ratio for a DC2R?

For those who don't know what I'm talking about, it is the ratio of wheel travel to suspension travel.

I have Toda DA's and I'm doing the maths behind valving / spring rate to try and find the optimum and compare to the dyno graph provided with the shocks..

Also, is a ride frequency of 1.5hz about right or should it be closer to 2hz?

Once I have the MR value I can then work out the current frequency which at this stage seems close to the 2hz range..

Thanks.

[tinkerbell]

when i installed DA6 rear LCAs on my DC2 - i did a bit of research on motion ratio as the strut mount point was further in to the chassis,

i found Honda-tech.com was most useful...

[ewendc2r]

ok thanks mate -- That was my next stop.. cheers.

I'll post up the results in any case so everyone can search here in the future lol

[ChargeR]

Be sure to post up the numbers when you find them. I have seen numbers on Honda-tech also but I would only trust them for rudimentary calculations. Best to DIY .

I have done some cursory suspension frequency calculations on my own car (DC5), using a java applet put together by a ClubRSX member and my suspension frequencies are around 2.9Hz front and 3.1Hz rear from memory. My suspension is pretty stiff and my car is hella track spec yo though .

EDIT: I think that frequencies in this range are getting a bit on the high side for Australian tracks.

[ewendc2r]

Yeah I think I agree, somewhere between 2.3 - 3hz seems about right considering we also don't develop a great deal of down force, & our tracks are a little bumpy in comparison.

Having said this I read a huge amount of information over the past two days and have gained a fairly complex understanding of vehicle dynamics and application moreso to FWD cars in order to ensure through a weight transfer situation (i.e. braking / accelerating, turning) that FWD traction is maximised.. It actually threw a spanner in the works suggesting softer front setup (inc. removal of Front ARB) and using the rear stiffness (combination of rear bar + wheel rates) with a small rear camber profile to induce rotation and ensure that during a weight transfer that lateral shift plants both front tyres into the ground firmly for traction (with the essential result being loading the outside rear tyre completely and effecting zero deflection on inside rear at point of lifting wheel). Without going into it, the rolling of the car essentially creates positive camber flattening the contact surface with the outside rear wheel in most circumstances (esp. trail braking into corner).

In any case the motion ratio for DC2-R seems to be:

Front - 1.5
Rear - 1.35

This is approximate obviously, anyone that wants to measure and confirm go right ahead but they seem safe to use for calcs at this stage.

So.. Now I can go through a weight transfer worksheet for corner-balancing & ideal wheel rates / damping. Its very interesting, takes a little to get around the physics concepts involved (because there are so many vector forces acting in combination) however its definitely logical..

By the way, what was also interesting was a debate between US setups and Jap setups.. i.e. Stiff rear & soft front vs equal leaning towards front stiff setup in Japan. There were valid points made in each case relating to various factors including track being smoother and more traffic to contend with thus factoring in a safety margin to increase stability as such but at the end of the day it remains a mystery because the physics are the physics and driver aside, there is only 1 perfect setup for any given track / condition..

[felixR]

thanks for the info ewen!

i'm not sure how i'm going to use that thou lol

[ewendc2r]

Well I can write up a very detailed explanation when I have time, I am confident I know understand the physics behind correct suspension setup for various requirements given varying weight transfer requirements & need for rotation..

I have also come across some useful spreadsheets to take out the hard work in calculations (just after I made my own simple version .. always the way) so when I have a moment I will post up.. Very, VERY interesting the result & I am confident that I will be able to shave considerable time off my previous QR clubman time (which btw was before I started modifying the car)... (1:06.8).. I would think shooting for a 1:03-1:04 is achievable given a small increase in average speed across the entire course however this is all talk until its done and that won't happen until I move back to brissie (im in cairns for work, and there are NO tracks up here for tarmac events with own car).

Glad you find it interesting Felix --

It was interesting the mis-information I found regarding LSD's as well, suprising considering the people commenting were very experienced and mech eng graduates etc .. Will post on this for everyones benefit as well (regarding 1 through to 2 way diffs and various types).

[ChargeR]

Interesting stuff ewen . I find this stuff a little interesting too but I am too lazy to measure motion ratios and the like for myself, but it only holds my interest for the time it takes me to realise that the flaws in my track performance don't lie in the area of suspension ride frequency .

I think it would be very worthwhile to measure all the suspension pickup points as it would allow you to calculate bump steer and camber curves which might be very illuminating when it comes to chassis setup.

[ewendc2r]

Well, the calcs i'm doing don't take into account non-level track nor tyre deflection. However based on the calcs and assuming an infinitely stiff tire wall (unrealistic, but I am not going to go into THAT much at the moment) we can then work out the preferred alignment settings inc. camber/toe/caster .. There is a lot of different theory on this, so I'll report back on it once I get the first stage sorted i.e. wheel rates and damping ratio for FWD (specifically dc2 r).

Incidentally, I think I've also landed a thing with Skunk2 USA for kind of sponsorship/relationship for remaining items as long as I review & report as well as be an "ambassador" for their brand .. See how it pans out in any case.. Not free stuff, but a significant discount, which might mean some group buys will be possible.

ChargeR -- Well, I'm not saying I'm schumacher by any length, but there were some parts of the handling of the car (even stock) that I wasn't happy with and definitely detracted from speed of the car. Its more about setting the best base platform to work with -- If you're coilovers aren't setup properly and the ARB's aren't correct then it is likely to be causing more harm than good (even over stock in some instances, as although a compromise, the setup from factory creates a nice balance) -- Geez, and here I was thinking that when I bought the coilovers that would be the end of it lol .. I've opened a can of worms here.. But hey, thats why we call it a hobby.