Looking for opinions on lightweight sound deadening...

[whammie 10+ year member]

Just like the title says, I'm building a widebody 240sx as my next project and everything on the car will be upgraded (suspension, performance, exterior and stereo). So addiung weight is not really an option.

It's a 1995 and while it was in the body shop I spot welded a few places to add rigidity to the frame (mostly for handling) but I also want the stereo to be as tight and rattle free as possible without adding alot of weight. The enclosures will be all fiberglass and as light as possible. but from a deadening standpoint... dynomat, fattmat, etc. is SO HEAVY...

I plan on injecting 3M spray foam into tight spaces and egg crate foam in large open spaces but any other ideas would be greatly appreciated.

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[OldOneEye 10+ year member]

Just like the title says, I'm building a widebody 240sx as my next project and everything on the car will be upgraded (suspension, performance, exterior and stereo). So addiung weight is not really an option.
It's a 1995 and while it was in the body shop I spot welded a few places to add rigidity to the frame (mostly for handling) but I also want the stereo to be as tight and rattle free as possible without adding alot of weight. The enclosures will be all fiberglass and as light as possible. but from a deadening standpoint... dynomat, fattmat, etc. is SO HEAVY...

I plan on injecting 3M spray foam into tight spaces and egg crate foam in large open spaces but any other ideas would be greatly appreciated.

You might want to talk to Rick of rammat fame. He did exactly what you are talking about and can share a few things that worked for him. Absorption is much lighter than mass loading. Also, part of the reason you want to mass load it to make stuff stiffer so it won't ring. There are other lighter ways of reinforcing panels (look at the inside of an older airplane wing or RC planes, they use a skeleton with a thin skin pulled over it... the skeleton gives it strength.

Juan

 

[Anthony Collova 10+ year member]

Go with vibration conversion. Use an elastomer.

The lightest are liquid dampers.

most common are water based dampers.

Do a search for these:

edead v 3

lizard skin

slealth kote

quiet car

second skin spectrum ( or sludge)

any of those will dampen vibrations by converting them to heat. they weigh very little and require very lin layers to be effective. The do add a small amount of mass which helps lower the resonant frequency of the metal panel, but most of the work is being don by converting the vibrations in to heat.. a very small increase...

using expanding foam can be good in some situations.. in the pillars it is good..

iof the expanding foam has any large space to shif in, it can break away from the panel and will squeak.... The pillars are perfect since they do not move a whoole lot....

Hope that helps

ANT

 

[OldOneEye 10+ year member]

With that said, most spray foam needs air to cure. You try to fill a big area and the middle which doesn't get any air never cures and stays gooey in the middle (giving little of the benefits your expect).

I would argue that most of the noise won't be coming in from the pillars anyway, but the wheel wells, firewall and trunk.

I've gone crazy on my own car (dynamat exteremeliner, dynamat extreme, dynamat hoodliner (used to absorb sound inside the area next to the rear passengers in a coupe), accumat 250 and accumat 750, but the foam is a pretty messy process that I didn't feel gave the best results the last time I tried it.

Juan

Go with vibration conversion. Use an elastomer.The lightest are liquid dampers.

most common are water based dampers.

Do a search for these:

edead v 3

lizard skin

slealth kote

quiet car

second skin spectrum ( or sludge)

any of those will dampen vibrations by converting them to heat. they weigh very little and require very lin layers to be effective. The do add a small amount of mass which helps lower the resonant frequency of the metal panel, but most of the work is being don by converting the vibrations in to heat.. a very small increase...

using expanding foam can be good in some situations.. in the pillars it is good..

iof the expanding foam has any large space to shif in, it can break away from the panel and will squeak.... The pillars are perfect since they do not move a whoole lot....

Hope that helps

ANT

 

[Anthony Collova 10+ year member]

With that said, most spray foam needs air to cure. You try to fill a big area and the middle which doesn't get any air never cures and stays gooey in the middle (giving little of the benefits your expect).
I would argue that most of the noise won't be coming in from the pillars anyway, but the wheel wells, firewall and trunk.

I've gone crazy on my own car (dynamat exteremeliner, dynamat extreme, dynamat hoodliner (used to absorb sound inside the area next to the rear passengers in a coupe), accumat 250 and accumat 750, but the foam is a pretty messy process that I didn't feel gave the best results the last time I tried it.

Juan

Totally!!!

Just saying that the only place I would personally use expanding foam is in the pillars, which actually do resonane quite a bit.. A very common place for higher end luxury cars to have OEM damper from the factory..

For road noise the wheel wells, quarterpanels and doors are the first places one should treat in a sedan type car.. Floor and firewall next..

For engin noise, treat teh hood firsrt tehen the firewall and roof

For exhaust, first treat the trunk or hatfch floor then the rear deck, lid and quarter panels... For anoverall quiet ride hit it all, if you can afford it..

a great way to reduce airborne sound is by first treating structure borne noise, with a damper, in this case a light weight one like a water based dmaper, then with a light weight foam, closed cell, neoprene or nitrile like ensolite... (which OOE might have mentioned in his first post)

that would be ideal way to reduce noise and save on weight..

 

[OldOneEye 10+ year member]

If you decide on using foam, you might want to try laying it down on the horizontal surfaces and then see how you like it (without glueing it). You might find you don't need the spray stuff there anyway. Usually you can't "try" anything like Dynamt with an adhestive attached, but with foam you can let gravity hold it or pressure fit it under your door panel and see how you like it. If you decide you need more, try the spray stuff.

Juan

Totally!!!Just saying that the only place I would personally use expanding foam is in the pillars, which actually do resonane quite a bit.. A very common place for higher end luxury cars to have OEM damper from the factory..

For road noise the wheel wells, quarterpanels and doors are the first places one should treat in a sedan type car.. Floor and firewall next..

For engin noise, treat teh hood firsrt tehen the firewall and roof

For exhaust, first treat the trunk or hatfch floor then the rear deck, lid and quarter panels... For anoverall quiet ride hit it all, if you can afford it..

a great way to reduce airborne sound is by first treating structure borne noise, with a damper, in this case a light weight one like a water based dmaper, then with a light weight foam, closed cell, neoprene or nitrile like ensolite... (which OOE might have mentioned in his first post)

that would be ideal way to reduce noise and save on weight..