Foam Filling

[twoqttsdad]

I've read elsewhere folks foam filling their hollow sway bar to get it more rigid or even foam filling their sub frame for stiffness. I've never crawled under the Kizashi but was wondering if anyone know if the Kiz has hollow sway bars.

Thanks. Two

[murcod]

Did they drill holes in the sway bar to get the foam in???

I'd just be concerned what could happen if the foam attracts/ traps moisture and the long term consequences. It's also hard to get it to entirely fill in smaller diameter/ longer crevices (if you're talking about the pressure can stuff?)

I tried to use it to fill up the gap in a dog kennel's walls once as insulation. I'd made the kennel with mini orb corrugated iron on the outside fixed to a wooden frame; then lined the inside with plexi glass to form internal walls. I tried to fill the gap in between through holes I'd drilled at the top in the wooden frame, I had trouble getting it to flow down to the bottom of the wall cavity. Then it would start expanding...... spreading the two walls apart (unevenly) instead of filling within the cavity! It was very messy and hard to clean up.

[KuroNekko]

I can't imagine that the foam will have any actual effect for stiffness. It sounds very unscientific. While I can see why people may hold the questionable logic that a solid tube is better than a hollow one, let's not forget we are talking about FOAM. I am quite sure what foam they are talking about too; it's like that stuff sold in Home Depot to fill holes and cracks, much like how Murcod described. The problem is that this stuff is NOT HARD AT ALL. Yes, it dries to a solid state and becomes firm, but it's still pliable and flexible, especially when encountering the physical forces of a chassis in cornering. I imagine it will have very very little to no effect in this regard.

If you have any of this foam around I suggest you play with it and see how it dries. I have, for home improvement projects. I can literally crack a solid piece of it the thickness of a sway bar with my hand with very little effort. It's not some kind of magic carbon fiber-esque substance with extreme rigidity. It's more impressive for it's thermal insulation properties and keeping bugs out from holes. In fact, I'd compare it to Styrofoam.

Also, about filling in the chassis with this stuff. I believe this is a practice born from misunderstanding. I am guessing it comes from people seeing this on some cars and mistakenly thinking it was for rigidity. I imagine it's actually for noise insulation. The foam would absorb and dampen road noise and vibration. Maybe some people saw this on some finer cars and probably incorrectly concluded it was for rigidity.

Regardless, if you can't guess from my writing, I think this is all very stupid. While foam will not add much weight, I can't imagine it will add much rigidity. What it does add is a mess and a waste of time.

If you want better chassis stiffness, get bigger and better sway bars with upgraded bushings. Get under chassis braces and get strut tower braces. Sway bars are known to have the greatest effect, however.
Also, the greatest improvement to handling is often always overlooked: better tires.

Again, foam sounds ridiculous. The whole misguided notion reminds me of 19 year old tuner boys with massive rear deck carbon fiber spoilers on their Honda Civics. Do they know that A) the car is FWD therefore downforce on the rear is not really helpful and B) that the car does not even go fast enough to create the amount of downforce that's even useful? I don't care if "the VTEC just kicked in, yo!" The car is not fast enough for the spoiler to matter.
I guess some people just don't think this through and it ends up as some horrible trend.

[LPSISRL]

Agreed 100%. Probably only good for noise dampening which may make it useful. But if it absorbs and holds moisture? Bad idea. I was wondering since the Kizashi chassis is so stiff anyway, are bigger sway bars really going to make a difference? I mean a stiff chassis was part of the design. In several reviews I've read, it was remarked that you would have to add a lot more horsepower to push the chassis to it's limits. I know that I would not be able to do that.

Edit:
OK, I just did some research. (aka googling) Apparently with the right type of foam, not the Home Depot type, it does actually stiffen the chassis. Go to post #14 on the link.

http://clubroadster.net/vb_forum/22-sus ... assis.html

[murcod]

Yes, foam is used to stiffen the body in a number of vehicles, plus reduce the noise transmission. But DIY, on a near new vehicle ..... perhaps on an old project vehicle you didn't really care about?

Sway bars don't have anything to do with body rigidity (as such), they limit body roll caused by weight transfer/ suspension movement through corners. A stiffer rear bar does make a huge difference to the handling on the Kizashi.

I'm just interested to know how on earth people manage to get the foam into the sealed bar without compromising it. I also fail to see it having any effect for the reason KuroN. pointed out. Much better to just upgrade the bushes first- if you can't afford a bigger bar! That can give a big gain for very little outlay. Even an upgraded rear bar for the Kizashi costs a similar amount to one decent performance tyre- cheap for the gain given.

[murcod]

Some more reading for anyone who's bored:

http://www.modified.com/projectcars/000 ... zx_part_5/
http://www.driftworks.com/forum/technic ... -foam.html
http://forum.miata.net/vb/showthread.php?t=24086

From one of the links:

Do not--I repeat--do not attempt to use cheap, hardware-store canned foam. This is not the same thing, and if injected into your chassis, will form a gummy mass that won't dry. Foamseal foam is a professional grade foam, which although it is a little unforgiving to cleanup mistakes, has superior mechanical properties and catalytic curing so it will dry even in an enclosed space.

In a final bit of reengineering to stiffen the body, we injected the chassis with catalyzed rigid structural polyurethane foam. Structural foam, in the 2 lb per cubic foot density that we used, can stiffen chassis members up to 40 percent.

Higher densities of foam can increase stiffness by up to 300 percent. Since we cannot retool custom parts to redo the Z's body, we figured that this would be an excellent, low-cost way of greatly increasing chassis stiffness. Injecting foam is not a new technique for chassis stiffening. The Infiniti Q45 uses this sort of foam in some of its chassis members to increase stiffness, as do a few other premium cars. In fact, the foam we chose is the foam recommended to repair damaged Q45s.

To get the correct foam for our project, we contacted Art Goldman, Foamseal's automotive product manager and author of an SAE (Society of Automotive Engineers) paper on the use of structural foam for the stiffening of automotive unibody structures. We used Foamseal's two-component foam kit, p/n 11-22 to fill the main members of the chassis. Like we mentioned earlier, Foamseal is the supplier that I-CAR, a national certification group for quality auto repair, recommends for the repair of damaged, foam-filled chassis. The Foamseal kit uses a two-part catalyzed polyurethane foam, which quickly cures into rigid, waterproof, closed-cell foam. To prep the car, we carefully masked off all painted areas anywhere where the foam could drip. As this sort of foam is a thermosetting catalyzed plastic, we realized it could be icky if it spilled on paint or any part of the car's interior. This foam is nasty stuff. It is impervious to all known solvents and cleaners.

[KuroNekko]

While I am glad to hear it's not the stuff from cans sold at home improvement stores (let's be honest, some sucker out there must have tried this), I still think this practice is questionable. The rust/corrosion issue and the lack of ventilation is a concern.

I also want to point out that the car referenced as having factory foam is the Infiniti Q45. This is not some small, lightweight car made for superb handling. This is a full size flagship car and I am far more inclined to believe Nissan used the foam for sound and vibration dampening than chassis rigidity. This car is the direct competitor to the Lexus LS and was called the Nissan Cima in Japan. The car died out due to low sales and now the top Infiniti in the US is the M.
These full size luxo cars like the Q45 are made for quiet, smooth refinement and not so much handling prowess.

I checked out the link that was first posted and it was for a Miata forum. Sounds like other links are discussing the Nissan Z roadsters. Not surprising given many obsessed convertible owners are desperate to try make their vehicles more rigid for better handling.
The reason is because they don't have a roof which acts as a structural brace. Despite the sporty looks of a convertible, it is known that coupe versions with a proper roof are more rigid than their drop-top versions.
I think I once wrote about this before but the Lamborghini Aventador Spyder weighs more than the coupe due to the extra braces to counter-act the loss of the bracing the roof naturally provides in the coupe version.

If I was that obsessed about convertible chassis rigidity, I think I would go for a roll cage which not only adds protection, but also adds chassis rigidity. Sure, it will weigh more than foam but I find this foam treatment somewhat of a snake oil. But hey, maybe it really works. However, I won't bother to find out.

More importantly, I think the Kizashi really does not need this stuff.

[Ronzuki]

My front porch roof's support posts are foam filled PVC. The load ratings were increased slightly by being filled w/ foam vs. not. What type foam I have no idea, but it would undoubtedly be an expanding type of some sort, heat activated or other.

I believe the foam applied to the inside of automotive A, B, and C pillars are for both sound deadening an structural enhancement. It is applied much like a caulk or sealant would be before components are welded together and is later activated to expand by heat applied in an oven-like environment.

[puckaveli]

It's all pointless really, unless you have tons of other suspension upgrades and drive the car on the limits of traction, which no one does on public roads, you will NOT notice a slightly stiffer sway bar and chassis.

[murcod]

It's all pointless really, unless you have tons of other suspension upgrades and drive the car on the limits of traction, which no one does on public roads, you will NOT notice a slightly stiffer sway bar and chassis.

I'd agree to disagree .

A stiffer body affects handling- and also decreases the likelihood of annoying traits like door rubbers squeaking going in or out of driveways, dash rattles etc. It could save your life in an accident if the passenger compartment maintains it's structure.....

I've got a stiffer rear sway bar and the difference is very noticeable. Even low speed cornering is vastly different, the higher the cornering forces the easier it is to notice the difference. Anyone on here who has one fitted will be able confirm this.