structural rigidity..........

[hilux30]

with all the suspension modifications that we do to our 240s, some of folks addressed this issue, but most have not. Espacially with S13 hatches, lets face it they are flimsy compaired to the S14. So now after all I did: springs, shocks, solid mounts, Energy bushings, its time to make the body stronger. Did anyone try expantion foam in the pillars and sills? "Sport Compact" mag. did it to an S13 hatch and they reported a good boost in rigidity. How much seem welding does make the body stronger? I don't feel like a cage, it's too not everyday kind of thing. I love my hatch but there are little too many rattles inside now to bear, and this is in Arizona mind you.

[BrianHarte]

The more stiff you make the car, the more uncomfortable it is going to be.

It doesn't matter if you do it with a cage, foam, welding, bars, etc.

I guess it depends on personal preference.

I chose to do things that I can remove.

I have tower bars, trunk floor bar, C pillar bar, bolt in cage.

All of the things can be taken out if desired and even sold if needed be.

[hilux30]

I think you are not understanding me: Stiffness in the suspension will make the car uncomfotrable, but stiffness in the frame or structure makes the car MORE comfotrable, quiter, less prone to deflection from bumps and handle alot better. There is a big difference. for example: Take a new nissan 350Z and a Mustang, the nissan has much stiffer shocks/springs rates than the mustang from the factory but still is more quit over bad roads because the frame does not flex, and that what makes it go around the track faster too.....

[hilux30]

excuse my spelling....

[gregfarz78]

There are people on here with a roll cage and kept their full interior intact

[simmode1]

I hate to sound like a fanboy, but if that chassis foam is good enuff for the new SCC s13, then it's good enuff for me!

I can't wait to do it...

[BrianHarte]

Hmmm, so basically you just want to fill the car with the foam, right?the end?

[93240cooool]

Hmmm, so basically you just want to fill the car with the foam, right?the end?

yeah i think thats what happens

[Philipio]

Make sure water/moisture can't get the areas you want to stuff with foam. We've all seen what happens to hatchback spoilers!

[Tsukiko]

I think you are not understanding me: Stiffness in the suspension will make the car uncomfotrable, but stiffness in the frame or structure makes the car MORE comfotrable, quiter, less prone to deflection from bumps and handle alot better. There is a big difference. for example: Take a new nissan 350Z and a Mustang, the nissan has much stiffer shocks/springs rates than the mustang from the factory but still is more quit over bad roads because the frame does not flex, and that what makes it go around the track faster too.....

i think theres a lot more to consider in the fact that a 350z may be faster (sorry i dont know either way if it really is or not, but that statement sounded just a little too uninformed for my tastes) around a track than a mustang...

also, a stiffer chassis (regardless of suspension) transfers more vibration and impact. therefore it is NOT more comfortable or smoother, in fact it would make your ride quality even more dependent on your suspension.

to put it simply, stiffer means rougher. Whether that be in the suspension or frame, it doesnt matter. obviously if you have stiff suspension such as coilovers then you stiffen the frame you will feel the difference more than a stiffened frame on stock suspension.

edit: Brian already did touch on this briefly, but it seems no one really paid that much attention, so yeah.

[BrianHarte]

I pretend to know what I'm talking about sometimes.

I did have a S14 that was stiff as f*** that I daily drove for years.

My new S13 is probably just as stiff.

[Tsukiko]

haha well you are the drifter whose leg everyone seems to be fixated on humping at least half the time, so you get away with it.

[hilux30]

NO NO NO, Stiffer frame does NOT mean stiffer and harder suspension!! I wan an engineer for a while for a big auto co. before I started my own business, I know what the hell I'm talking about, but I'm not going to be an a**hole and dog all who didn't dump tens of thousands of dollars to learn this s*** :When the unibody is "stiff", meaning the torsional and cowl stiffness is high, means LESS noise, harshness and vibration is transmitted to the cabin, better suspension allignment and better handling, espacialy over rough roads. NOW when the unibody is stronger, it allows you to through stiffer shocks and springs without upsetting the unibody. Ever wonder why convertibles the A-pillar or windshield frame always shakes more than the rest of the car? because you cut the roof and the UNIBODY is weaker, that means you must soften the springs to keep it form falling apart. ALSO ever wonder why M3's suspension is almost track ready yet it's so comfortable? The Mustang and 350Z thing assuming they both put out the same power to wheels, its well known the nissans chassis is FAAAAR more superior and better sorted. The foam thing is used even today on expensive cars from the factory, it just made public for us to benefit from it because it works, it light and you only use in pillars and rocker panels, not in the hatch where is makes no use at all.

[dc1984]

for some reason, i feel like everything u are saying about a stiffer body is 180 degrees from the truth. i do believe that the stiffer u make ur car (suspension and/or frame) is going to make ur car a less comfertable ride.

and dude, if ur so knowledgable and experienced in all this, then why the hell are u in here asking questions.

[jesse53]

If you an engineer then you should know energy is not destroyed but transfored most likely to the least stiff thing that will absorb it,the driver

[hilux30]

If you read what I was asking about you wouldn't be talking out of your a**, All I asked was did anyone seam weld there hunk of crap before I invest my time and energy stripping the car, and if anyone used that new foam that’s out. And no DC1984 I'm not talking 180 deg. from the truth, the sad part non of you ask intelligent questions and discuss anything without jumping on everyone’s back, But just rather say what you THINK is right. I keep have to remind my self that there are only a handful of people here that know that the hell they are talking about and the rest are just filler. Just forget it's hopeless!!!!!!!!!!!!!!!!

[japslapsilvia]

structural foam has been done before. most of the pics are gone, but info and data is there

edit

ok so i cant post link to another site. go to FA under "best of 240sx and its a few post down.

[KoopaTroopa]

Although I'm not an Engineer yet, i'm still a mechanical/aero student.

If you have x suspension on a car then say you turn the frame into something as stiff as if it were solid titanium then yes, the ride quality will be more harsh on you then before. All that extra energy from driving over say, train tracks, which would slip passed the suspension now is translated to the flexible parts of the car. That diminishes the energy your body absorbs. Now in a frame were nothing moves, the only thing left to receive that energy is the driver. That doesn't mean that your going to have a stiffer and harder suspension, just that the ride quality on the same suspension won't be as smooth. Regardless of what suspension you have some energy will get passed it.

As to making a more rigid frame. I haven't looked into that foam stuff but it sounds messy and irreversible. You could use stiffer engine/transmission mounts, using the engine's strength to stiffen the body. It would be loud though. Or you could weld an under body brace. Something the shape of an X would probably work well.

[musashin]

Damn, this guy has something uncomfortable shoved up somewhere uncomfortable, if you know what I mean.

And if you have lots of rattles, why don't you directly fix the rattling parts themselves?

[BrianHarte]

The stiffer I made my car, the more rattles, noises, bumps, etc. I felt.

[livinglegend2100]

blah blah blah! big words! Big Words! BIG WORDS! rabble rabble rabble

try and ditch that high and mighty "engineer" status and trying being fxcking humble about it.

http://lmgtfy.com/?q=seam+welding+240sx+

arse.

[KoopaTroopa]

hahahaha, let me google that for you. That's priceless. I'll definitely be using that often in the future

[scheffler]

Ok this is not going to go any where. Engineers are very stuburn I know I am one and work with them all day. honestly there are valid points on both sides of this argument. Yes a stiff suspention and week unibody equals noise and vibration i think we can all agree with that. Also a gokart with no suspention and a stiff frame equals bouncing and rattles and noise.

Makeing the unibody stiff will help out but you are not going to make a nosie making rattle of a car completly quiet i am sorry you wont, but it will help. When I stitch welded my car it didnt really help with the noise it made it a little beter but I also have no carpet or anything like that so take that for what it is. I have not put foam in yet so i dont know what that will do to the noise. I do know that it greatly improved the haddling and response of the car.

If you dont want to hear anything that makes noise they make this stuff called dynomate and carpet that will greatly reduse the noise that you dont want. M3 i belive also have this from the factory to reduse noise.

but the noise was not enough to keep me from welding the body it is a good mod.

[livinglegend2100]

yea dynomat works wonders. as well as carpet. i also have a stripped interior and i can vouch for you in saying that you hear EVERYTHING. but to be honest i prefer it. i like being able to hear all the noises my car makes. especcially when its a bad one.

ive heard of a couple of people that used the foam inside the pillars and what not. said it worked pretty well. but if you need to get into those areas for something your pretty much s*** out of luck

[mrflip69]

look in the best of 240sx section in Fresh Alloy. There's a write up on foaming the frame rails and most of the chassis. The guy used this 2-part mixture stuff.

Moisture might be an issue, but the type of foam used is closed cell I believe? so as long as your prep is good, you should be ok. The guy never really followed up if rust was an issue. People argued back and forth that water would get trapped and cause rust, but figure if the water can get in, it can hopefully get out.

Stiff chassis will amplify any strength/weakness in your suspension. Good coilovers would be a start--by stiffening the chassis, you're letting your suspension work more effectively/efficiently

[scheffler]

I dont even think he cares any more cause his last post he was like "just forget its hopeless"

So any way

[hilux30]

It is not about stubbornness or engineer status or any of that crap. There is confusion here between "stiff" and "strong", "chassis" and "frame" all I know right now is the knowledge I have didn't come because I read it somewhere, no it's from research and design, from extensive work on projects, some of you said valid points BUT for most part there is great confusion. There are frequencies in vibration that change from one part of the body to the other, THEN the suspension comes in and THEN it is a s*** load more of math to be done. You can NEVER have a uni-body that is too STRONG or STIFF; yes it is true it's the holy grail of structural rigidity!! Then the stiffness of the suspension is designed, the bushings, spring and shock rates, sub-frame and so on. The Stronger the uni-body, the more is dissipates impact energy, and that is not "destroying" energy like someone up there said, it is spreading the shock through the whole body without the passengers feeling it. But there is allot more to it than what I can tell you know, it will take months and years to get it down.

I conclusion: I know that if I stitch weld my 240 and use that foam, AND maybe a proper welded cage, my uni-body will be strong as hell and I know that there will less noise and harshness coming from the road, less rattles, less squeaks and it will handle allot better than know....

[hilux30]

I do care because I have ridden in many 240s where the owners did everything to the bushings, the mounts, coil-overs, bla bla bla and so on and they ride horrible beacuse no one bothered to make it stronger.....

[livinglegend2100]

not knocking your knowledge. at all. clearly you know a lot more about this than me, and a lot of other people on this site. but you realize this is no lexus right?

mind you, if the people whos cars you rode in had aftermarket bushings and coilovers and all that jazz. im pretty sure they didnt buy them with the intent to get a "kushy, quiet" ride. most coilovers suck bigtime when it comes to bumps, vibrations, etc. but theyre not meant to give you a comfortable ride. theyre meant to perform.

240's make noise. they vibrate, wobble, clunk, scrape, and you can bet your gonna feel all of it. its just a part of life when you drive a 17 year old car.

in my honest opinion, if i were you i would foam the pillars and other various hollow points in the body, dynomat the hell out of the interior, invest in some strut braces, stitch the s*** out of it, and accept the fact that a 1992 240sx will never ride, feel, or be nearly as quiet as a new car.

just my .02

[Shabbernigdo]

honestly ide be a bit worried about adding the foam. i know the s13 is pretty flexable but if you go and stiffen up certain areas thats use to give and flex where will that energy be transfered to if the area no longer flexes?

i know idealy the car body should be rock solid and the suspension should be what takes up the bumps in the road but its hard to say if the inital designers did or dident add in the fact that there chassis was gonna flex and give a bit when they did the origonal planning for the s13 suspension set up and design.

Now if you are doin a total tear down and rebuild where you are gonna gusset and stitch weld and such to add structial support then i wouldent worry so much about adding the foam other then the obvious moisture holding it tends to do.