# Where to strenghten the body?



## Yes (Jul 21, 2004)

Hi all,

Since i´m new to these forums let me introduce myself a little bit.
I´m a 21 yo guy living in sweden who has, quite recently, fell in love with a red little she-devil called S13. Of course after getting the car things started breaking down - clutch, bushings, differential, paint and rust, to name a few things. While lesser men would have despaired, I started working on insane ideas of tuning the car to perfection... and that´s where we are now.

In maintaining the idea that S13´s should be made to take corners like Ferrari´s I have ran in to a 'small' problem with my plans. Unfortunatley(for us, not the Ferrari´s) S13´s seem to have a rather weak body. That´s not very good and obviously needs improvements.
A cage will of course solve some of the problems but it´s crucial to strenghten the weak spots in the body structure to get best results. The question is, however, where are the structures weaknesses? Has anyone here made any measurments? That knowledge would be a real time saver. 

Cheers! :cheers:


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## 180SX-X (Sep 21, 2003)

what model do u have...coupe or FB...in da FB, u obviously need to brace the back between the piullars,some strut bars...and a cage would basically solve it...


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## Joel (Jun 11, 2003)

front strut tower brace
rear strut tower brace
rear floor brace
front power braces
adjust to neutral toe
-2.0deg camber front, -1.0 to -1.5deg camber rear
as much castor as you can get
rear subframe align and lock kit
replace all bushes
wide tyres on 17" rims

half cage if you are that hardcore


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## schebs240 (Apr 13, 2004)

Nissmo power brace
Rear lower tie bar does alot of good for a cheap price.


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## Yes (Jul 21, 2004)

Oh, sorry, I forgot to mention it´s a hatchback. Here in sweden we mostly got S13 hatchbacks with CA18DET, so it´s easy to forget to be more specific.

Unfortunatley I don´t think just mounting some braces will be enough. What I have to look at, to get the results I desire, is where the body is weak and build a full cage around that information. When just bracing you will probably cause new weaknesses when the newfound rigidness puts more force on other parts. The car will of course work better, but I don´t think that it will achieve optimum performance.
Now, one might argue, a full cage with a front subframe should be what you´re looking for! It is, I think, a very good idea. The problem, however, is that there are regulations on how the cage can be integrated with the body. For best support you´ll need some kind of WRC-type(or other serious racing-type) of cage, and for that you´ll need a license. A subframe might also not be so good if i´ll want A-arms instead of McPhearson for the front wheels(I do want that, but there might be legal issues in the way).

Oh well, I hope you understand how i´m think here. And I also hope that i´m thinking right - I really need far more knowledge about these things than I posess.

:cheers:


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## OPIUM (Aug 18, 2002)

Yes said:


> When just bracing you will probably cause new weaknesses when the newfound rigidness puts more force on other parts. The car will of course work better, but I don´t think that it will achieve optimum performance.



I would suggest tearing the car apart and seam weld everything. That is basically the only way to get as much structural support out of the body as possible. Well the only way I've heard anyways. My ears are open if someone else has any other suggestions...


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## Yes (Jul 21, 2004)

I have considered doing that, but I have met som scepticism about the whole idea which makes me want to do some research before I put down all that work. The thing is i´ve never seen any figures on the improvements it is said to make. I´ve only seen alot of talk about it, but no facts. So I don´t know, perhaps it works and perhaps not...
One thing is for sure though, you can get a very strong monocogue without seam welding everything. For example, Saab 9-3 SS - 16000 foot pund/degree. Compare that with Viper Le Mans - 13600 fp/degree - or Lamboghini Murcielago(which has a tube frame supported by carbon fibre) - 15000 fp/degree. Now, the 9-3 Sport Saloon is a pretty regular car(at least here, I don´t think it sells too good outside of europe) with a point welded monocoque. So atleast it´s not cruicial to seam weld for a good rigid body, however it might still improve things.

:cheers:


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## OPIUM (Aug 18, 2002)

yeah the only reason I could see that there is no real data supporting this theory is that not alot of people do it due to the amount of work involved. Not to mention the fact that the people [like you and I] that would actually do all this work don't really have the necessary equipment/resources to measure said findings with anything other than a g-meter in their ass. The obvious downside to all of the seam welding is the added weight. So if your a big weight junky like I am.. I'd say the only way to accomplish your goal is to do all the bolt on stuff mentioned above by Joel, with the addition of Tension Rods, Rear Toe Links, Rear Traction Links, Rear Upper Control Arms, and some sway bars and well matched spring/damper rates. But thats about as far as my knowledge takes me at this point in time...


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## Yes (Jul 21, 2004)

Yes, good point there.
I have now tried to consult some litterature on this matter, but did not find too much. Carrol Smith, however, recomends seam welding in his bokk 'Tune to Win' - and I do believe he´s a man who´s knowledge it is safe to trust. But there´s that question of weight, which I did not think of before you mentioned it... hard decision wether it´s worth it or not.

:cheers:


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## Joel (Jun 11, 2003)

You are comparing hi-spec expensive purpose built race cars with a cheaply made Japanese domistic market, low end sports car.
The only source of knowledge for the S series chassis rigidity would be the JTC (Japanese Touring Championship) team sites. The problem is they are in Japanese. Try searching for Daishin.


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## OPIUM (Aug 18, 2002)

A translator like Bablefish may help then...

http://babel.altavista.com/tr


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## motoracer47 (Jul 23, 2003)

I think the teams that would have done the measurments, proly wont share that information based on the expense involved and the competative advantage it would give the competetion. Of coarse im not talking about jgtc as they dont race the s13 anymore, but in lower national jap classes that would, im sure its guarded info. I dont think that seam welding would add all that much weight, denpending how you weld, you would not be adding much metal to the structure, just bonding the extisting metal in more places.


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## 180SX-X (Sep 21, 2003)

the firewall area is a pretty weak place...check NPM for a brace the helps this problem...


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## Joel (Jun 11, 2003)

is the firewall a factor in chassis strength at all? I mean its tack welded in!


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## Slo_240 (Jan 1, 2004)

One thing nobody mentioned was fender braces. J-spec put some on their project S13 and they said it made the whole structure of the car totally different. I would definately invest in those and what everybody else has mentioned.


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## Joel (Jun 11, 2003)

Isnt that what a power brace is?? I mentioned that.


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## Slo_240 (Jan 1, 2004)

Oh my bad I didn't see that. I knew thats what they called it also I just skimmed through it really fast. Credit for Joel.


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## Yes (Jul 21, 2004)

motoracer47 said:


> I think the teams that would have done the measurments, proly wont share that information based on the expense involved and the competative advantage it would give the competetion. Of coarse im not talking about jgtc as they dont race the s13 anymore, but in lower national jap classes that would, im sure its guarded info. I dont think that seam welding would add all that much weight, denpending how you weld, you would not be adding much metal to the structure, just bonding the extisting metal in more places.


It´s true that they probably wont share any information considering the competitive aspect. Fortunatley though, you can make measurments really cheap. The greatest expense would be a couple of new windshields, since it´s easy to crack them when twisting the car. If your interested, here´s a little description of how it´s done:
http://hem.passagen.se/hemipanter/ (scroll down to 'Chassis and components').

Biggest problem here is of course all the work involved.

Now i´ll just have to try the babelfish translator on som JTC pages. Thanks for the tip!

:cheers:


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