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DemosT
Joined: 26 Jun 2025
Posts: 15
Location: Italy
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 Posted: Sat Nov 29, 2025 10:19 pm Post subject: Sound deadening recommendations? |
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Hey all.
Any recommendations for sound deadening materials? My '83 924 gets kind of annoyingly loud at highway speeds and while by no means deafening it sure is irritating.
I am thinking of applying it in the trunk area under the carpeting and perhaps under the rear seats and on the floor.
I suppose another quick way to cut down on noise would be to change the damn engine mounts but no foreseeable luck with that.
I have seen that alo-butyl stuff being recommended over the foam, but what actually works best at deadening that buzz at high speed? |
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Cedric
Joined: 27 Aug 2004
Posts: 2776
Location: Sweden
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| Posted: Sat Nov 29, 2025 11:17 pm Post subject: |
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Is it exhaust drone, road noise or wind noise?
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1980 924 Turbo
www.instagram.com/garagecedric/ |
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DemosT
Joined: 26 Jun 2025
Posts: 15
Location: Italy
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| Posted: Sun Nov 30, 2025 12:14 am Post subject: |
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| Cedric wrote: | | Is it exhaust drone, road noise or wind noise? |
Not sure ATM, i could check tomorrow but i believe its mostly road noise and some exhaust if not a bit of all three. |
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924RACR
Joined: 29 Jul 2001
Posts: 9013
Location: Royal Oak, MI, USA
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| Posted: Sun Nov 30, 2025 1:09 am Post subject: |
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One question might be how much of the original padding you still have...
I ended up removing quite a bit of my original padding (US-spec 82 931), between the mix of it being somewhat rotted and wanting to take the weight out.
Now I'm wishing I still had it, as I too have quite a bit of noise, mainly road noise it seems, at anything above around 50mph. The car is just tiring to drive for an hour or more, from the noise level.
The original padding even included a fair bit of heavy rubber-like padding (dense foam maybe?) on the trunk floor, as well as a lot of stuff on the floor which was rotted and no longer there. I think there was also a felt pad on the trunk floor, and a rubber sheet on both sides of the firewall - all now gone.
I think I'll be aiming to add back in new stuff on all three spots; as I also want to get in and replace the carpet with new before long (probably with the new kits from J West Engineering), will be the perfect time to reinstall noise protection. I'm thinking some of the lighter/thinner stick-on mat (like Dynamat) on the floor and maybe also trunk floor), felt at least on trunk floor and firewall, plus probably also heavier rubber-based stuff on the firewall.
It'll be a fair bit of weight - but the extra boost more than makes up for it, thankfully!
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype |
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DemosT
Joined: 26 Jun 2025
Posts: 15
Location: Italy
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| Posted: Sun Nov 30, 2025 5:19 am Post subject: |
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| 924RACR wrote: | One question might be how much of the original padding you still have...
I ended up removing quite a bit of my original padding (US-spec 82 931), between the mix of it being somewhat rotted and wanting to take the weight out.
Now I'm wishing I still had it, as I too have quite a bit of noise, mainly road noise it seems, at anything above around 50mph. The car is just tiring to drive for an hour or more, from the noise level.
The original padding even included a fair bit of heavy rubber-like padding (dense foam maybe?) on the trunk floor, as well as a lot of stuff on the floor which was rotted and no longer there. I think there was also a felt pad on the trunk floor, and a rubber sheet on both sides of the firewall - all now gone.
I think I'll be aiming to add back in new stuff on all three spots; as I also want to get in and replace the carpet with new before long (probably with the new kits from J West Engineering), will be the perfect time to reinstall noise protection. I'm thinking some of the lighter/thinner stick-on mat (like Dynamat) on the floor and maybe also trunk floor), felt at least on trunk floor and firewall, plus probably also heavier rubber-based stuff on the firewall.
It'll be a fair bit of weight - but the extra boost more than makes up for it, thankfully! |
Mine still has the original sound deadening, though you can just tear it straight off since the collagen is obviously long done for.
If im gonna go through with this i think i'll apply that alu-butyl stuff wherever i can fit it (in the side storage wells and spare wheel space too) and then smack the old deadening on aswell for good measure.
As for weight, eh i don't care much about speed at all (which is why i went with a 924 in the first place) as much as i want something stylish and that i can use for highway trips. Oh, and that works with the sound system i've built for it. |
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924RACR
Joined: 29 Jul 2001
Posts: 9013
Location: Royal Oak, MI, USA
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