Bens handling the big issues.. N12 Coilovers (56k + drool)

BQ.05.TD · Post by **BQ.05.TD** » Fri Sep 15, 2006 9:26 am

man i seen your weld in cage and had to empty my sock. its fukn horn i love it. i would love a more serious cage for strength and saftey but its still a daily driver. yer i new cams ditched the desighn a few years back but meh. it will so do the job and i dont plan on doing 10s lol

but i have a few other braces that i have ot get right and when there done it should be pritty damn stiff.

it was funny b4 i put the cage in if ya jacked the fron on the car up and wheels of the ground when ya opened the drivers door it would get a little bit stuck and drop down when it opened cause the chassis was bending just that little bit. but now with the cage its the same if its on the ground lol

cheers justin

Post by **The Renegade** » Fri Sep 15, 2006 9:35 am

Post by **Ash** » Fri Sep 15, 2006 9:50 am

The Renegade wrote:Here's Timmzys Pix

thats some impressive work! very neat and tidy. is this thing finnished? would love to see some complete pics!

Wes · Post by **Wes** » Fri Sep 15, 2006 11:26 am

Hey Daz, ive had prices of $2500 for a 4point cage! :-s!!

I would love to get a cage as yes, i agree, i dont feel safe and a roll over would be the end.... And to help improve overall rigidity

Im just thinking how id go about road licensing it as a daily driver though....

Ben Hewitson · Post by **Ben Hewitson** » Fri Sep 15, 2006 12:22 pm

i'm going for a half cage so its still registerable in SA.

BQ.05.TD · Post by **BQ.05.TD** » Fri Sep 15, 2006 3:43 pm

yer ot have it regoed with a half cage u will have to tak eout ya back seat and get it re regoed as a 2 seater. cause there is just not enough roon between ya head and the cage in the back. u can get a full 24point cage engineered and road legal as long as it meets al the specs.

and holy fuk $2500 for a 4 point cage. damn thats a bit steap. i payed 500 fo rthe spare et that has over $400 worth of sway bars, $400 worth of springs and shocks, and cage and all the otehr bits and pieces

Timmzy · Post by **Timmzy** » Fri Sep 15, 2006 11:39 pm

Thanks Renegade!!

I don't do the picture thing often enough to remember how to!! How sad is that!

Boosted, I noticed the same thing about jacking the car up!! hahaha. Made it heaps easier to line the doors up once I had painted it all. To be honest its made a lot of things like that easier.

The car is more or less complete, minus a turbo and front skirt and interior. I will try and take some more photo's soon, withing the next couple of weeks when I get the turbo back.

If you are going to do cage like mine, you have to basically say to yourself that 'yes I am prepared to write this shell off if I roll over or get done by the blue'. Unless you know someone who can really 'help' you.

I justified that because I think the base value of our shells is not much. Its the bits bolted to the car that are of value. So I thought I can always sell or re-shell if needed.

I can't wait to get it on the track but this turbo and getting exhaust manifold ceramic coated are killing me $$$$ wise.

Darren.

Callumgw · Post by **Callumgw** » Mon Sep 18, 2006 1:02 pm

Just had a read through this discussion after not doing for a week or so. Just thought I'd like to clarify something, how sway bars resist body roll. They only reduce the roll of the body relative to the wheels (and other unsprung bits). So if you but on the biggest sway bar imaginable the body will still roll relative to the ground. To stop this effect you need to look at the height of the centre of gravity and the roll centres of the suspension geometry.
This is easily demonstrated by the picts you see of FWD cars with their rear inside wheel of the ground in a corner. There is still body roll, but the sway bar is stiff enough to lift the inside rear wheel. At that poiint its CoG vs Spring.

If you do this on the front the effect can be disasterous. PLease note there a whole lot more to this than this simple outline I've put here, try this article:
http://home.iprimus.com.au/dillonp/fwd/fwd.html

http://www.turbomopar.com/handling.html

Ben Hewitson · Post by **Ben Hewitson** » Mon Sep 18, 2006 3:00 pm

true. but with a FWD if you leave the back end to flap about in the breeze you'll find that it will pull the chassis with it. those FWD's you see with the inside rear tyre waving around in the air are not setup as well as those that reduce this effect. some interesting pointers in this artice;

"But in FWD a big front bar has conflicting effects: it still increases understeer by overloading a front tire, but conversely it decreases understeer because the more heavily loaded tire is now driving instead of dragging"

"But if FWD rear suspension is just along for the ride, and anti-roll bars are no longer terribly effective, then stock chassis stiffnesses could be adequate."

My answer to this is simple. The stock N12 chassis IS NOT adequate.

some other pointers that have been given to me are, to increase the spring and shock stiffness as well as torsional stiffness of the anti-roll bars in a FWD to help keep the back of the car flat. if your rear suspension is too soft and rollie then the outside rear tyre will compress most of its travel and leave the inside rear wheel to hang in the air or to unload the spring so much that its non-effective.

This will allow the chassis to roll over to the weighted side, and as most FWD's are fairly short the chassis will unweight the inside front tyre as well and cause roll understear. not a pleasent driveing atitude i can tell you.

my arguments for increasing front and rear anti-roll stiffness in an N12 exa is becaue the chassis is not realy up to the task by itself. my lowering the car and reducing the centre of gravity as well as ensuring the car stays as flat as possible in the corners will result in a better handling car and less understear.

since i have modified my suspension the exa has vastly imporved its corning ability to the point where i dont have enough power any more to light up the inside front tyre or cause it to power understear or tramline.

Other imporvements include the cars ability to change direction. i noticed that when i hit some fast chicanes the car doesn't twitch or become unstable in when trying to turn the steeringwheel the other way. The car also brakes a lot better. with reduced dive its making the tyres work harder and still allows the car to shift weight. Acceleration is greatly increased because the back doens't squat and allow the front to lift as it did before. also there is very little acceleration lift from the front of the car which means the energy is transfered into motive power instead of being wasted tangentally into the shocks and lifting the car.

i took a friend for a drive for the first time in my car the other day and he's owned an EXA for longer than i have. he said that if he tryed that in his car he would have understeard into and out of the first corner at hlaf the speed and ended up over the armco and down the cliff to our left...

Ben Hewitson · Post by **Ben Hewitson** » Mon Sep 18, 2006 3:05 pm

Callumgw wrote:Just had a read through this discussion after not doing for a week or so. Just thought I'd like to clarify something, how sway bars resist body roll. They only reduce the roll of the body relative to the wheels (and other unsprung bits). So if you but on the biggest sway bar imaginable the body will still roll relative to the ground. To stop this effect you need to look at the height of the centre of gravity and the roll centres of the suspension geometry.
This is easily demonstrated by the picts you see of FWD cars with their rear inside wheel of the ground in a corner. There is still body roll, but the sway bar is stiff enough to lift the inside rear wheel. At that poiint its CoG vs Spring.

in response to this, you are absolutely correct, but you need to also include that the car has weight and momentum. if you dont have enough anti-roll stiffness when the car gets up onto that outside set of tyres it will continue to move out due to centripital force. adn once it does the inside wheels are uselss.. you need to make the car move as one.

for example the car becomes a fulcrum in a corner and the cornering momentum will exert itself away from the centre of movement and also upwards. if you can keep the inside wheels on the ground, by allowing the outside suspension to not compress and pull the car over your going to get better handling. you will definately put more pressure on the tyres and you may exceed their grip levels by doing this. but you can always get better tyres cheaper than fixing a sloppy chassis.

if any SA ET owners want me to take then for a drive once i've got new rear springs and shocks, or even as the setup stands now, your welcome to contact me.

Paul Smith · Post by **Paul Smith** » Mon Sep 18, 2006 11:00 pm

I bought those adjustable Koni's from Wes. I was going to get CMS front struts but I think they would be way too stiff for my liking. I'm guessing I'll end up with just the Koni's, a rear sway bar and strut braces. I'll see what that's like and then go from there.

Callumgw · Post by **Callumgw** » Tue Sep 19, 2006 7:28 am

Ahh Ben, What a can of worms. A few quick things: Yep we drive a sow's ear. Actually as early FWD turbos go it was all that bad, but by modern standards this little toy's suspension is very dated. Newer vehicles are so much better.

there are some rules of thumb that people like Carrol Smith have used for sway bars and springs, I'll try to remember to look them up tonight.

There is a classic quote from a promanent racecar engineer within the book "inside racing technology". The quote says that Balance is paramount. Meaning that a car that has balanced grip can be driven faster and more consistantly that one with lots more grip at either end. There are some excepts from this book here:
http://www.insideracingtechnology.com/contentspg.htm
but I don't think that particular quote is there.

My current set up is: King Springs all round with standard front sway bar and Whiteline rear EXA bar. (these are on an exa). This gives a big improvement ove standard. The front is soft enough to allow for grip without unloading the inside tyre to much. The rear tends to trail oversteer, giving quite a neutral car. When I final get round to putting Bill's LSD into the car (bought it back in 2004 and been waiting on bl**dy builders and babies before I can get back to work on the car) I'll probably uprate the front bar see how it goes then. The LSD should then combat the reduces loading on the front inside wheel. But this'll all probably lead to more rear bar.........

Ohh, Something else is important here! Chassis stiffness. The ET and EXA have low stiffness and bracing is a great idea, front top AND bottom rear tops, and anywhere else you can think of. I'll probably go down this route together with the front sway bar. Otherwise the improvements will have a much smaller result.

C

Ben Hewitson · Post by **Ben Hewitson** » Tue Sep 19, 2006 8:31 am

yeah. nice work callum. good info.

as has been outlines in that quote, the balance is the key, but also note that he mentiones the rear bar. i believe thats my problem at the moment. i'm getting a fair bit of roll understear that is generated by a slack rear end. hence the dual rear sway bars going in when joof sends me one. lol.

as for the front end. i've decided to go the 27mm custom sway bar and i'm in the process of madding an N13 strut brace to fit (thanks to BQ.05.TD for that info). once thats done there isn't a lot i can 'bolt on' to enhance the chassis.

the exa has a rear parcel shelf so theres' no need for a rear strut tower brace. but i'm thinking about uprating the rear springs and shocks. see how they go. i'm also keen on some Yellow adjustable top Koni's.. see how that pans out.

Callumgw · Post by **Callumgw** » Tue Sep 19, 2006 8:55 am

Hey Ben,
I think there is a bit more that can be done front and rear. The EXA does have a parcel shelf but it is flimsey and a bit far forward. I still intend to put something further back between the towers. Quite posibly with a bit of diagonal support, either to the parcel shelf or to the bottom of each tower or both. For the front end, the upper brace is a good start but the lower attachments are a but soft in my opinion. They are basically a canterlevel with no support at the outer end. Bracing from here would be good, I'm still mulling this one over as to what would be best though.

Roll understeer may be because you've gone to low. Sounds wrong doesn't it? Well consider this: We should be using negative camber, and we all set up the car for static negative camber. So when the car is still the camber is negative. But this is not he case when the car is in the 'rolled' corner condition. Immediately you'd say, ahh the tower is compressed so there would be MORE negative camber.

WRONG!, the layout of a MacPherson Front end comes into play here. If in the static position the inner pivot is BELOW the outer pivot (ball joint centre of rotation) then the geometry of the wheel will become more positive as the strut is compressed, removinf all that good negative camber.

Now with mine, with King springs the inner pivot IS below the outer pivot in the static position. So I know I am getting a positive camber change in the bends. I'd bet your the same.

Please note I said you MAY be too low. I don't know your set up and there may be several other things that are effecting it, tyre size, tyre stiffness, tyre block patterns, spring rates (going to fixed rates may improve this over Kings variable rates, but with other side effects), damping, suspension set up (Toe, Kingpin Incl, CASTER! etc).

C

Post by **The Renegade** » Tue Sep 19, 2006 9:49 am

Callumgw wrote: For the front end, the upper brace is a good start but the lower attachments are a but soft in my opinion. They are basically a canterlevel with no support at the outer end. Bracing from here would be good, I'm still mulling this one over as to what would be best though.

Hey Callum, have you seen the lower braces that you can get for a Honda S2000? They're lower braces. I think there's something you can get for a WRX too.

N12 Turbo Forums

Bens handling the big issues.. N12 Coilovers (56k + drool)

Sway bars and body roll.

Re: Sway bars and body roll.

Springs, shocks, roll bars and chassis stiffness

Bolt ons

Re: Bolt ons