Urethane foam injection for increased chassis rigidity...?

[yannis-supras]

I've been reading an article related with a japanese tuning company called Sun Line Racing and on one of their numerous project cars, an S15 Silvia, that they prepared for ultimate handling at the Tsukuba circuit they injected the sidesills and mainframe with urethane foam for extra chassis rigidity. What do you people think?
I mean, I can understand that this is a pure racing application but would this method apply to a street driven mkii/mkiii? I also understand that the correct rigidity and flexibility of the certain type of urethane is required in order to prevent transfer of stress in other areas of the chassis structure.

Since I'm in the middle of my suspension/body work now it would be the right time for me to do this. Do you think it will result in creating an extra stiff, untolerable for street use chassis or will it add up on the chassis rigidity nicely?

Also if someone has a specific and clear opinion on this matter can they please suggest the appropriate type of urethane foam for such an application?

 

[Mr.PFloyd]

it works. they do it all the time for flimsy r32 skylines and such. i have only heard of it use of track cars but im sure it would be awesome in a dd car.

 

[yannis-supras]

CryoSlash I have done some stich welding on the seams of my mkii's body already and I'm planning to do some more. So combined to that I don't wanna end up with an extra stiff chassis. Anyone that has a 1st hand experience on this?

 

[Sl1dewaysSupra]

I thought about it as well to stiffen up the front end.

 

[turbogate]

I remember when Sport compact car magazine had their project Z car, one of the issues was about doing what you mentioned, and it was a street car. and as you mentioned it, i found the link
http://www.sportcompactcarweb.com/projectcars/0006scc_project_nissan_300zx_part_5/
Scroll down to "Foam-Filling the Chassis"
It was an interesting article. I'll go ahead and re-read it now

Later

 

[Sl1dewaysSupra]

I think alot would depend on the compound( 4lbs, 8lbs etc.) and where you injected it. Just remember to drill relief holes every inch and a half or so. That way you don't twist and warp the chassis.

 

[IJ.]

Longterm it's not so great as it loses it's bond inside the rails and squeaks like a bitch ! (past experience with a mates 510 rally car)

 

[turbogate]

The article mentions that there are some cheap foam versions out there. The Foamseal seems to be a good product, i just found it in that website that only sales race parts. If cars like the Q45 and high end luxury cars use it, i wonder if its a matter of the quality of the product. I hope the racers on this forum can elaborate on this some.

 

[yannis-supras]

I remember when Sport compact car magazine had their project Z car, one of the issues was about doing what you mentioned, and it was a street car. and as you mentioned it, i found the link
http://www.sportcompactcarweb.com/projectcars/0006scc_project_nissan_300zx_part_5/
Scroll down to "Foam-Filling the Chassis"
It was an interesting article. I'll go ahead and re-read it now

Later

Greg That was a great article, Directly related to the subject, those Sport compact guys seemed really amazed with the results. And daily driver friendly too!!!

...Just remember to drill relief holes every inch and a half or so. That way you don't twist and warp the chassis.

Good point, I'll keep that in mind if I decide to take that route.

Longterm it's not so great as it loses it's bond inside the rails and squeaks like a bitch ! (past experience with a mates 510 rally car)

Ian you have to be a killjoy don't you :naughty: :icon_bigg. I think it also depends on the material used too. If you use plain wall stuffing polyurethane foam it will just not cure properly. Those Sport compact guys used an automotive specific product that Nissan factory uses on Infinities http://www.sportcompactcarweb.com/projectcars/0006scc_project_nissan_300zx_part_5/photo_07.html.

 

[GotToyota?]

I believe the new Ford trucks inject the frame/chassis with foam for sound deadening.

-Matt

 

[IJ.]

Yannis: This was done MANY many years ago so yes new vehicle specific products have to be better I was just relating my experiences with it.

It's a very messy time consuming job for minimal gains as I'm not sure on a Mk2 but the Mk3 under car rails are low volume so won't really add anything in rigidity, filling the Sills may show some gains!

 

[yannis-supras]

Yannis: This was done MANY many years ago so yes new vehicle specific products have to be better I was just relating my experiences with it.

It's a very messy time consuming job for minimal gains as I'm not sure on a Mk2 but the Mk3 under car rails are low volume so won't really add anything in rigidity, filling the Sills may show some gains!

RightyO sir, sometimes I forget how old you are and you go way back in the day :biglaugh: .
MkIII have a much more rigid and firm body compared to the mkII. I haven't checked my mkIII donor car's mainframe but I'll take your word for it . The mkII though has quite wide, beefy mainframe rails so I think there's gains to be achieved there too.

 

[IJ.]

Probably a good time to do yours as well as it's been out of the weather for awhile so will be nice and dry inside the rails!

 

[yannis-supras]

My thoughts exactly Ian, plus the car will be resprayed inside out again so it's much better to do that process prior to that. No major headache on worrying if I make a mess that way . I just want to make sure that foam injection won't result in an extra stiff chassis that would render daily driving unbearable. Good thing there's density grades so you can predetermine things.

 

[IJ.]

If the Chassis is ridged you can tune the suspension to give the ride quality you want/need!

This is the ideal situation (most cars are a huge compromise and take chassis flex as part of the ride comfort equation)

 

[bwest]

I don't know that you could ever have too stiff of a chassis (brittle, yes) as it would allow the moving parts of the car (suspension) to do their job. but also realize that some force that was transfered from the suspension into the body (as flex) will now be more localized on suspension mounting points. In some vehicles these are designed as weakspots for accident and repair reasons reasons (any formula car based off a tub) as its cheaper to replace suspension parts (including uprights) than the tub itself.

Just a thought.

 

[bwest]

IJ beat me to it....

 

[yannis-supras]

I think I'm almost convinced on this. Right where do I get the right materials from...? :runaway:

 

[Sl1dewaysSupra]

I know that they use the same stuff on boats so I would try a marine supplier(SP?). If not try Pep Boys, although I doubt they carry it they might be able to point you in the right direction on were to obtain it. If all else fails I would look on the web in places like Summit and race oriented sites.

 

[yannis-supras]

I just googled "Handi foam" for the last half hour or so...It doesn't look promising, there's only very few places in the states that sell it as well as a couple in the u.k.. Main problem is that it's a flammable, highly pressurized product so shipping abroad is a NO NO :icon_conf and secondly that stuff is expensive too. About $200-250 for the required quantity excluding "smuggling fees" :aigo: :naughty:!!!