Chassis foam injection

[Tire Shredder]

I've heard it mentioned on other forums but never discussed here so I thought i'd introduce it! The general idea is to fill critcal frame and chassis components with light weight, strong urethane foam to increase chassis rigidity without increasing weight (much). about 10lbs would do the whole car, and leave it a lot stiffer than it was to begin with...without adding steel or special fabrication!

It's something I've dreamnt about doing someday. Anyhow, I finally found somebody that actually did it on a street car, with real qualitative results! check it out.

http://forums.freshalloy.com/showthread.php?t=162693

the author notes much less chassis flex including a more solid feeling over train tracks and much smoother. much more tire fireedback and can feel his suspension doing it's job. The overall chassis is quieter aswell! better ride quality, handling, turn-in and overall chassis responsivness.

I don't know about you guys, but i'm thinking this would be awesome to fill our flex-y rear subframes with.

I know I'll be doing it when I restore my car someday.

[Junkie]

More stuff for moisture to accumulate ??? These things have enough issue with that as it is ;)

[RedP85]

:stupid: I really don't think it is a good idea up here.

[Tire Shredder]

well, obviously wouldn't put it in high water areas like door bottoms, quarter panels etc. The foam does have a 0.02% water absorption rate and it's 99.9% closed cell construction, so the foam won't retain any water itself, or allow any to pass through it. as for general condensation, if air and water mixtures can get in, they can get out through natural convection..

also, these airgaps where condensation can form should be minimized by the foam...the goal would be to have no air gaps. and in the areas where there are air gaps, leave a vent/drain hole.

daimler chrysler did a test on an SUV and found significant increases in chassis rigidity when placed in joints. it can be found here: http://www.sae.org/technical/papers/1999-01-1785

I am a member, and think I will purchase the paper.

the foam in question..http://www.foampower.com/store/two_component/index.html

[Dave A.]

I can't quite see how a flexible foam would make a chassis more rigid, though it would definitely help with dampening road noise to some extent.

[Tire Shredder]

it's not very flexible dave. check out how strong it makes this already crushed can!

http://www.youtube.com/watch?v=A1AHgkWzGqE

[pdupler]

I think the significant factor is "Can you eliminate rust inside the frame before you fill it with foam?" Its actually an excellent idea for new cars and lots of manufacturers do it and the difference is quite a contrast. But if we have any rust inside the frame, then there will be poor adhesion of the foam. Flexing of the frame will further deteriorate the adhesion, eventually leading to air gaps where there is already rust and may, probably will, make the situation worse. Ideally, you would want to have the whole chassis dipped in an alkaline electrolysis bath to de-rust first. That would get all the rust out of the nooks and crannys and ensure complete adhesion of the foam. Another thought would be to somehow paint the inside of the frame through the various weep holes with a rust encapsulator like POR15 before foaming but not sure how to do it or how well it would work.

[Tire Shredder]

I think the significant factor is "Can you eliminate rust inside the frame before you fill it with foam?" Its actually an excellent idea for new cars and lots of manufacturers do it and the difference is quite a contrast. But if we have any rust inside the frame, then there will be poor adhesion of the foam. Flexing of the frame will further deteriorate the adhesion, eventually leading to air gaps where there is already rust and may, probably will, make the situation worse. Ideally, you would want to have the whole chassis dipped in an alkaline electrolysis bath to de-rust first. That would get all the rust out of the nooks and crannys and ensure complete adhesion of the foam. Another thought would be to somehow paint the inside of the frame through the various weep holes with a rust encapsulator like POR15 before foaming but not sure how to do it or how well it would work.

yup, for sure. problem is such a process is so invasive that the chance of you ever 100% coating everything internall is pretty low. after dipping a chassis and painting/coating as best you can some areas maybe left untouched, leaving it potentially worse in some areas than factory. aside from dipping the chassis in a vat of epoxy sealer (like lexus, bmw and hyundai do) and spinning it to remove air bubless...there isn't really an ideal way to do it. The best thing I can think of in our situation is powder coating, since paint will be electrically attracted to any bare metal. at least, in theory. problem is getting the powder close enough to the said bare area that it will attract.

[benchwarmer]

This is really intriguing. I live in the dry Southwest where rust isn't really an issue so I might add this to my list of things to try. Seems a bit pricey for the benefit, though.

[Tire Shredder]

two II-22 kits would do the trick, about $100 with shipping to do the key parts of the car.

considering the cost, time investment and weight of seam welding, buying strut braces etc. I think it's dirt cheap. All of those upgrades would likely be heavier than the foam too. Not that this can be a substitute for the upgrades, but in conjunction with them you have the possibility of having a very stiff chassis.

[Supra_devil]

i've thought about doing this to my supra as well. mostly for noise absorption. the good quality stuff used for automobile applications isn't supposed to hold moisture like regular insulating foam that you would use in a house, so i'm thinking as long as you fill the area with some good quality rust proof or a rust neutralizer before applying the foam it should work quite well and be worry free.
the rear control arms i am definetly thinking about doing since they are known to rust out.
i am far away from that stage though, so maybe one of you will beat me to it and i will have a good guide.

yannis-supra did some, pics in post 32
http://forums.celicasupra.com/showthread.php?t=23034

[Tire Shredder]

Bah! thanks Glenn. This is a serious repost then.

[Austin E]

Alot of the newer cadillac's use this stuff, and other higher end car's. We had to get certified in using it in auto repair. But, i have never heard of someone just installing it until now, i'm intrigued.