Okay so I could run an MBC without problems correct?

 

Yup. The way I read that rule is you can change anything up to and including the wastegate actuator and spring as long as you don't make any changes to the wastegate itself.

 

Read this:

http://zzyzxmotorsports.com/library/...h-20070918.pdf

 

Confused . . . what is that supposed to show us? Is it trying to show that having the RC migrate toward the inside of the turn is better than to the outside? Is it trying to show that keeping the RC as high as possible is better?

Can someone elaborate? And also, can anyone share what all the important measurements are for the EVO?

 

This is what I'm trying to tackle now. Measuring a car by hand is quite difficult and analyzing said measurements is even more difficult.

That said I do have a basic ACAD layout of the front suspension for the evo. Just having had a second child I haven't had anytime to do analysis.

I think the idea behind keeping the RC high is that the "moment" arm between the CoG and the RC is kept short and thus the car rolls less and requires less spring & bar and aids in compliance I guess. That was a sweet run on sentence.

Evolutionary you have PM.

John

 

SP Weight Reduction

ok...here's my list of weight reduction mods I've personally done or weighed and their weights. All items are SP legal. All weight savings are from stock weights.

Odyssey Battery PC680 16lbs saves 19lbs
GSC Battery Tray 1.5lbs saves 0.5lbs
Invidia Catback Exhaust 25.5lbs saves 11lbs
Buschur Air Filter 1.5lbs saves 2.5lbs
Buschur LICP 2.5lbs saves 1lb
Buschur 3" DP w/heatwrap 9.0lbs saves 2lbs
ACT Prolite flywheel 10.5lbs saves 3.5 lbs
Works Poly bushing set 5.5lbs saves 1.5lbs
Ohlins Flag front damper w/spring 15.5lbs saves 6lbs per side
Ohlins Flag rear damper w/spring 10.5lbs saves 0.5lbs
Tein RA front damper w/spring 14.5lbs saves 7lbs per side
Tein RA rear damper w/spring 9.5lbs saves 1.5lbs
Sparco Pro2000 19lbs
Bride FG seat rails 9.0lbs, 28lbs total saves 9.5lbs
Buschur coated "ebay" O2 housing 3.5lbs saves 6.0lbs
OEM tools 1.5lbs
OEM Jack 5lbs
Spare tire 32.5lbs
Trunk Floor & Carpet 7lbs
Trunk liners 7.5lbs
Radio Head Unit 4lbs
Speakers 1lb each (4lbs total)
Megan tubular manifold 9.5lbs saves 5lbs
IC sprayer tank 5lbs
Rear floormats 1.5lbs
5zigen FN01rC 18x9.5 w/285-30-18 V710 47lbs gains 2lbs
Front brake shields 0.5lbs per side
Extended lug studs 3lbs gains 1lb
Wing 8lbs
Intake manifold bracket 2lbs
SPAL Rad Fan 2.5lbs saves 6.5lbs

UNSPRUNG WEIGHTS

Front
Hub & Upright: 19lbs
Hub & Upright w/axle: 26lbs
LCA: 7lbs
Damper: 15.5lbs
Wheel & Tire: 47lbs
Rotor: 20.5lbs
Caliper & Pads: 10.5lbs
Approx Unsprung weight: 115.25lbs per side

Rear
Haven't measured yet!


I'll add some more to this post one I weigh some items. I'll also add a few suspension measurements.

John

 

Nice info!

 

You want to minimize roll center migration. I think (and I'm kind of new to this stuff, so don't take this as gospel) that if the roll center migrates outside the track you get a jacking force instead of a roll force, i.e. the suspension will either compress or extend on BOTH sides as you add force, depending on whether the roll center migrated to the inside or outside of the turn.

Now here's where it gets complicated: there's a roll center for the rear axle as well. If you draw a line between the two roll centers, you get the roll axis. This is the line that the car rotates around as you add cornering force. As the suspension moves, both the front and rear roll centers move, and the axis of roll is no longer through the center of the car.

Assume for a second that the rear roll center is fixed. In the case where the front roll center moves to the outside of the turn, your roll axis is now slanted across the car. This will cause the car to lean not only to the outside of the turn, but to the rear as well. You'll put a lot of weight on the outside rear tire, and tend to lift the inside front.

From what I've gathered, there are a couple of basic guidelines for roll centers:

1. Get it close to the CG of the car in the front and rear.
2. Limit roll center migration.
3. Make sure your geometry doesn't cause a roll center to go "underground".

There may be others. I haven't been studying this stuff for too long. Steve from ZZYZX is on these forums and he really knows his stuff, so maybe he'll chime in and correct my errors.

 

the roll center in really poorly named. It has nearly nothing to do with the point that the car actually rolls around. It's a calculated point where all of the forces in the suspension members have no moment component to them. Higher roll centers will transfer a larger portion of the lateral load transfer through the suspension memebers instead of through the springs. Roll centers further away from ground level (above or below) will introduce jacking forces that will raise or lower the car due to lateral force. It is for this reason most race cars will have roll centers near ground level. There is a strong argument for strut suspensions to have above ground roll centers to limit the damage from the terrible camber curves without running overly agressive spring/swaybar rates. In no case do you want the roll center 'as close to the cg as possible'. A couple of inches above ground are sufficent.

Analysis of the roll center in any position other then the static suspension position is mostly an exercise in futility because there are too many unknowns (namely the actual forces generated by each tire in a dynamic state). Also to actually calculate the 'roll center' one would have to take into account forces in all suspension members, including tie rods, which most types of simple roll center analysis don't. Given that evo's in SP trim transfer nearly all of their weight to the outside tires, the important characteristic to keep track of in the rolled condition is the outside suspension instant center (that's where most of the force is coming from). Limiting the loaded side instant center to stay above ground in the max rolled condition might be a decent goal to set but even still there could be compromises that allow it to go under ground ("there's no way i'm running my car that high just to keep the IC above ground!" type deal...)



if I had the points to model the suspension I could model it, I've just been too lazy to do it myself when the car already works as good as it does.

 

Hmm... this is enlightening:

http://zzyzxmotorsports.com/library/...nd-reality.pdf

I've obviously picked up on more myths than facts. However:

And here's what I think is the important concept from the article:

So it looks like the simulation of the KRC (kinematic roll center) movement vs. body roll, while it doesn't have any direct application to the actual physics that are happening, is a useful tool to tell us if the geometry will result in stable behavior.

 

This thread needs some bump.

Go Giants! {cracks open beer}

New Toys!~ 18x9.5 NTO3. V710's on the way.

 

https://www.evolutionm.net/forums/sh...53#post5237153

Here is a group buy on the lightest BIG wheels you can get. 18x10 +35 and only 16 pounds!!!

We need a few more people to get the group buy to go ahead.

EVOlutionary

 

They really need to start selling those here on a regular basis. I'd be all over that if I had the cash laying around for it. Unfortunately, I'm fielding a LeMons car as well as co-driving a 6-national event season this year, i.e. I'm broke.

 

No doubt. If a company were to nut up and import 10 sets I'm sure they could sell them off in probably less than 6 months. . . Don't forget, they are also fitment for the 350Z rear wheels . . .

EVOlutionary

 

Hmm... JSC Speed just happens to be an EvoM vendor. And they just happen to sell stuff for the Z. And I just happen to know a guy who works there... Maybe I'll drop a hint.