the practice of inserting mixing foam between vital chassis parts in a unibody car to stiffen it........i thought it was pretty cool...maybe that and seam welding and you have a nice road race car?

 

Road race cars usually need to adhere to some sort of rules and foam isn't allowed by any sanctioning body that I know of (in the US anyways). A well designed roll cage should stiffen the chassis enough for whatever you want to use it for.

Also, in the event of a fire, I wouldn't want 50 lbs of foam to burn and create toxic fumes. But that's just me.

 

Some OEM A-pillars are epoxy-filled for strength. That would add a lot of weight if you did it to the entire chassis, though.

You could also just add more seam welds in the unibody. That's all Nissan did to stiffen up the Nismo 350Z. (December '07 Super Street, page 104)

 

Finding foam that will stand up to a car beating on it will be tough. Most will start breaking down with a little bit of flexing.
The flamability issue is also reason for concern. Ever started the Great Stuff expamding foam on fire? Look out!
You'd also have to worry about whatever water does get in, now doesn't have a way to get out. So, the car will probably rust faster than if left alone.

 

They mention this practice in JDM insider by APEXi Japan in an R32 GTR demo car. The benefits were that it was lighter to use expanding foam in key structural places than say a full race cage. Not much more was elaborated on and I don't have any first hand experiences. I would not recommend this for race cars (track regulations) but possibly if you are building a street car, but at your own risk.

 

they did this to the skyline on street tuner chalenge...
I have done allot of work with the urethane foam that they used and I kinda thought it was a stupid Idea.. dot to mention when your replacing a panel later and you weld and it catches on fire inside

want stiff do a cage

 

There is foam that doesn't burn.
It's along the same basic principle as the honeycomb they use to use.
I'll bet it works pretty good when done right.
50lbs of foam would not fit, likely not even if you filled the cabin...
We used it on storage tank buildings for the oilfield.
It made them crazy stiff, allowed us to use lighter gauge steel.

 

Ford Sierra Cosworths had foamed rockers from the factory. Makes rust and body repairs difficult.

 

Thank you for some sense of sanity. Most of the rest have demonstrated their lack of knowledge. Yes there are plenty of foam products that are fire resistant. and the concept of its use to increase stiffness is sound. Also, the quantity requried would be far less than they have proposed. It souds like a good concept and I have often thought it could be extended to body parts such as fenders to reduce flex as well.

 

Why is a flexing fender important? It isn't, but you think it is. The aftermarket has sold people on the whole 'chassis flex' and rigidity issue so much so that everyone thinks that they need more of it. Well, if you and your car are fast enough to warrant stiffening the chassis, then your need for a roll cage will satisfy that as well as the need for rollover and impact protection. Or are most cars not that fast but they want another mod to brag to their friends about?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nfn15037 &raquo;</TD></TR><TR><TD CLASS="quote">Why is a flexing fender important? It isn't, but you think it is. The aftermarket has sold people on the whole 'chassis flex' and rigidity issue so much so that everyone thinks that they need more of it. Well, if you and your car are fast enough to warrant stiffening the chassis, then your need for a roll cage will satisfy that as well as the need for rollover and impact protection. Or are most cars not that fast but they want another mod to brag to their friends about?</TD></TR></TABLE>

i dunno i just heard about it..........i have a k24/k20 in my coupe right now and i want to avoid the cage, since i live in socal and if i get pulled over and have the hood popped im screwed