tuning gurus, maybe you can help!

[-Fred-]

i'm in desesperate need of a good setup for the Opel/Vauxhall Speedster/VX220 (whatever the name is)

i've tried the setup i'm using on my ZZ-S and on my Elise, to no avail.

the thing simply snap/oversteers when i lift the throttle, it's a nightmare to drive... i'm usually pretty good with tuning, but i can't do anything with that one!

if anyone could help, i'd be eternally grateful! (well, not eternally, but for a good while )

 

[Jpec07]

Have you tried using a softer compound tire on the rear than the front? that usually gives me a great deal of understeer on most cars. The Speedster is pretty good on stock settings, if you power it up, go easy on the acceleration. Widen the gear ratios to avoid initial slipping, (hard on acceleration though). Also, try raising the LSD initial Torque thing by increments of 3 until you're comfortable with it. Lower the rideheight, and try to use as soft a tire as possible. Also, minimize the spring rate. I hope that works for ya.

 

[Gil]

I can't remember offhand whether the Opel has the higher spring rate in the front or the back. Whichever it is switch them. Keep them the same distance apart.
Also, try raising the front end to knock out the oversteer. (increments of 2-3 till you're happy with the handling.)

 

[boombexus]

Man, that car just plain sucks. But you know who rules with that car is Made in Holland.
I actually have got some of his settings that he used for that car. I'll post them up here soon.

 

[Power Slay`d]

I'd like to spend same time on it over the weekend.
I'll post my findings on Monday.
Just remember the car is 900 Kg heavy has little down force and the engine is in the back. Then it has a sort wheelbase. (That's makes it like trying to make an arrow/dart fly backwards.) The balance is wrong and there is now momentum to carry the front with the back. Try shifting the weight to the front by lifting the back. That is just theory and there is a **** loud of things to take in a count.

Hay! The car was made like that.

 

[Duke]

Punk: I haven't really driven the car except for the TT that uses it, but...

Powerslay'd isn't quite right - raising the back will put more weight on the rear wheels, not the front. Unfortunately that is static weight distribution.

Weight transfer is what's doing you in. You need to resist forward weight transfer from deacceleration. The two basic moves are to stiffen the front springs and stiffen the bound on the front shocks. They work together and you will need to do some of both.

Stiffening the front springs [in]directly limits the amount of weight that will be transferred to the front. You don't want to go too stiff, or the car will not rotate because too much weight will stay on the rear wheels. So you need to complete the equation:

Stiffening the front bound has no effect on the amount of weight transfer, but it does control the rate of transfer. So stiffening the front will slow down the change in weight distribution and will help prevent the rear from unloading suddenly. This should make the car more stable under deacceleration.

Hope this helps,

Duke

 

[tezzell]

As always, it is a learning experience. Nice break down Duke and still impressed with your knowledge.

 

[-Fred-]

well i've made it better, but it's still not what i want it to be...

i've come to the point where i'm actually thinking it's the car itself, and not the setup, that is messed up! so i'm going to let it dust itself in a corner of my garage, right aside the RX8 for a good while!

thanks for the help, everyone!

 

[sukerkin]

There's no shame attached to finding a car doesn't suit you Punkrock.

For me the VX220 handles just fine; not great but OK. I think that PD included the early version of the car in the game, the one prototyped before Lotus was asked to sort out the suspension. Even with that help, the Elise (of which the VX is practically a clone ) is still a better car, it just doesn't have as many frills (radio, carpets etc ).

If you'd like me to post up some settings I'd be glad to but, driving styles being such a variable, I can't promise that they'll make the car any more to your liking.

 

[CrackHoor]

Originally posted by neon_duke
Stiffening the front springs directly limits the amount of weight that will be transferred to the front.

It's my understanding that stiffer spring have no effect on actual weight transfer, they just reduce the nosedive/squat that is a symptom of that transfer under decel/accel. This dive/squat is bad because it eats up suspension travel and also causes the car to take more time to stabilize in a corner.

Great stuff n_d, but this quote caught my attention and I thought I'd throw this out there for discussion...

 

[Duke]

Originally posted by CrackHoor
It's my understanding that stiffer spring have no effect on actual weight transfer, they just reduce the nosedive/squat that is a symptom of that transfer under decel/accel.

C-H, you are exactly correct, and thank you for pointing it out. I typed directly in the other post when I meant indirectly. Karts have no springs at all and obviously they do transfer weight.

You are correct in saying that the springs do not limit weight transfer, and you're also correct in what you say about dive and squat. That's what I was getting at by "indirectly". Springs do affect dynamic weight transfer through movement of the roll centers of the car's mass. The roll center is based on the car's center of gravity and the suspension geometry - and it involves engineering well beyond my limited understanding.

Weight transfer is affected by wheel rate, which is the measure of stiffness or resistance to vertical motion at the the wheel. Softer springs lower the wheel rate of a given pair of wheels, and therefore transfer less weight between that pair.

This is coupled to a theory of dynamic weight transfer called 'wedge', which is a measure of the relative amounts of weight transfer across the car at both front and rear. More equal weight distribution at the rear than at the front is called positive wedge, and causes understeer. More equal weight distribution at the front is called dewedge, or negative wedge, and causes oversteer.

So stiffening the front springs and shocks of Punkrock's car will cause greater weight transfer across the front of the car than at the rear, wedging the car more, and reducing the snap oversteer he is (or was) experiencing.