924Board.org

brealytrent · Joined: 28 Dec 2008 Posts: 414 Location: Goldsboro, NC

As I am just about to finish my semester and begin to enjoy summer, I finally have time to get back to working on the 924 again. Since I've got some rust to contend with, I'm removing the carpet from the passenger compartment to get at it. While I'm doing this, I would like to do something to quiet the interior.
Mine's an early car with almost no sound deadening. the rubber/foam that was on the passenger side of the firewall crumbled in my hand from being soaked for so long. In addition, the only 'sound deadening besides that and the pad covering the transmission tunnel is this cardboard-like stuff the factory put on in the pockets in the rear quarter panels. I'm tired of having to crank the radio to unreasonable levels to hear my music while driving! For the most part the issue seems to be vibrations running through the structure of the car, as it's mainly a very low bass rumble that's the most noticeable. It would also be nice to block exterior noise outside as well. I'm not concerned with weight, however price is a factor.

TL;DR - I want to make my car quieter on a budget!
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1977 Porsche 924 - sold
1980 Porsche 931 - sold
1984 Porsche 928 'S2' Euro - sold
2016 Ford Fiesta ST - sold
2009 Porsche Cayman

Cedric · Joined: 27 Aug 2004 Posts: 2818 Location: Sweden

Take a look on how the later cars are insulated. But I guess you have the old rear suspension, which will be noisier. My track 931 is pretty quiet on long journeys, it has all oem insulation left. There is some pretty heavy thick damper mats under all carpets, including rear boot compartment, those would probably bee good to have. To get rid of some aero noise i mounted new version door seals (the newer ones are thicker and have an extra lip), which worked excellent.
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1980 924 Turbo
www.instagram.com/garagecedric/

Grenadiers · Posted: Thu May 16, 2013 8:41 pm Post subject:

Trent, if you and your Dad come up this summer, you can take a look at my carpet collection. Not sure how much insulation is there. How's that 931 coming along?

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'83 944 Track car.
'88 924S Track car.
'89 944 Turbo
2004 Winnebago Vectra monster RV
2012 Jeep Wrangler
2014 Kia Soul
2001 Ford F350 powerstroke

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

If you're looking for a whole-car solution, I've read really good things about "Lizard Skin", although I've not used it myself: http://www.lizardskin.com/sound-control-insulation.html

I've also used Dynamat (http://www.dynamat.com/products_car_audio_introduction.html) product to insulate the speaker enclosure areas (door speakers and rear speakers), and was pretty happy with the results.
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erstwhile owner of just about every 924 variant ever made

kcoyle · Joined: 15 Jan 2011 Posts: 712 Location: Long Island, NY

There's some good info here.

http://forums.rennlist.com/rennforums/924-931-944-951-968-forum/514372-making-the-944-quiet-with-pictures.html

I added some McMaster Carr part #9709T26 when I had my interior apart.
I think it did help somewhat with vibrations.
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1982 931- Stock with MBC at 8psi

Relax, all right? My old man is a television repairman, he's got this ultimate set of tools. I can fix it.

dubrict · Joined: 22 Apr 2011 Posts: 150 Location: Horseheads NY

The cheapest thing you can do that you'll find well-discussed on forums all over the internet is to use roll-on roofing material from your local hardware store. This material is rubbery-sticky stuff on one side, and shiny tinfoil on the other side.

It's basically the same concept as dynamat. Works great on your floors, but not as well on doors. But it's a lot cheaper.

I used it when I tore down my interior, and it did make a big difference. Didn't transform it into a luxury-quiet car but it is a lot better now. I only used it on the floor, not the firewall or the sides.
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1979 924 NA
2009 Chevy Impala
2005 Dodge Dakota

Crazyirish · Posted: Mon May 20, 2013 6:36 am Post subject:

If you check out the auto enthusiast sites the current trend in sound deadening is to use CLD Tiles (Typically Butyl Rubber & Aluminum - The cheapest form of which is the roofing material mentioned earlier) to get about 25-50% coverage, then a layer of Closed Cell Foam in 100% coverage to decouple the sheet metal from the next layer. The final layer is Mass Loaded Vinyl - also in 100% coverage as the final barrier.

I will be doing my 924 turbo up like this and will report when finished, but based on all reports, this treatment makes most cars sound as quiet or quieter than a brand new luxury vehicle.