GR86 Soundproofing / sound dampening

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Potatoman

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This car at 80mph is loud, and I think we can do better :) Does anyone have experience at adding soundproofing material?
  • Have you done it yourself or have you let a company do it for you?
  • What material did you use?
  • What was the subjective and objective reduction in noise?
  • I've read that even if the decibel level doesn't go down as much, it might still sound better due to lower resonance, is that true?
  • Where in the car did you install the material? (boot, inside doors, inside quarterpanels etc.)
  • Can you recommend any shops that can do the installation?
For reference, I measured the cabin noise with an app called Decibel X and it gives me about 74.5 decibel at 60mph, and 77.0 decibel at 80mph on a nearby A road with a pretty rough surface area.
 
On the first generation car I put quite a bit of effort in adding sound deadening to it. It was quite a common thing to do as its easy and relatively inexpensive.

I used a combination of silent coat 2mm and 4mm deadening matting, stuck to the body, foam isolator sheets between the door and door cards and 3M insulated acoustic thermal insulation wool (effective and very light) fitted in the recess of the interior panels and any nooks and crannies. MLV is a very effective product but it's not as easy to work with and can add alot of weight. All in all I added 11kg. The difference is noticeable, it doesn't suddenly turn into a rolls Royce but it's definitely quieter and it doesn't sound like your in a rally stage when you hit a bit of loose material.

I ended up doing it in stages and by far the most effective areas to target were the rear wheel wells, it's right behind you ears and the huge void under the rear quarter windows seems to make things worse. Second area after that which were equal was under the rear seats and the doors. I did't bother with the boot, everyone loves to do it but since you don't have anyone in there it's pointless, the rear bench does a good job isolating noise from that end of the car especially if you have done the rear wheel wells.

I have some photos somewhere I'll have to dig them out. Fortunately with it being a Japanese car the interior comes apart very easily so it's definitely a DIY weekend job when the sun's out.
 
I used to run a Nissan 200SX (S14a) where the road noise and all sorts of squeaks and rattles used to drive me nuts... Whilst my GR86 at speed is certainly not as loud as that, I agree that we can do better!

I spent a couple of weekends in my old Nissan applying a very similar sound deadening strategy as Matt had suggested:
  • Cover the door skin and rear wheel wells metal skin with butyl sound deadening mat
  • Cover the door cards and rear wheel arch trim with said sound deadening mat
  • Stuff the void between the rear wheel arch and trim full of mineral wool loft insulation
  • Identify any rattling dashboard trim and pad out with foam tape where necessary
Made a massive difference! You might want to take a look at these Noico sound deadening mats from Amazon; I bought some to improve the acoustics of my living room, got some left over so might try sticking them in my GR when I get a chance!
 
Hey All 👋

First post to this great community.

I've searched but can't find a specific thread on sound deadening so I'm curious as to what approach members have taken?

I don't think the car is too noisy per se but poor road surfaces are magnified in how they create a 'roar' inside the car.

I don't want to deaden the entire car but I think it could benefit some smart placement of material.
 
Excellent. Welcome to the forum, and I look forward to reading your research and following your advice :)

People have put some deadening in when changing door speakers, but I'm not sure much more has been done yet.
 
I went with

KILMAT 80 mil (2 mm) 18 sqft (1.7 sqm) Car Sound Deadening Mat​

Doors: 1 piece in each door - as part of the Focal speaker install
Rear seat: 2 pieces in each seat well. [4 in total]
Boot floor: 4 pieces

Didn’t want to disturb the interior carpet so I have 2-4 pieces left over.

Is it worth it?

Not sure how much of an improvement it’s made because I only managed 16 miles before fitting the speakers and sound proofing.

However, the car is very solid with an absence of vibration - my impression is the Kilmat makes a worthwhile contribution.

It does not eradicate road or tyre noise but may have reduced noise levels over stock.

Other forum members should be able to provide better insight but I have no regrets. BTW the Focal speaker upgrade is excellent.
 
GR_Fungle said:
Hey All 👋

First post to this great community.

I've searched but can't find a specific thread on sound deadening so I'm curious as to what approach members have taken?

I don't think the car is too noisy per se but poor road surfaces are magnified in how they create a 'roar' inside the car.

I don't want to deaden the entire car but I think it could benefit some smart placement of material.
Click to expand...
Hello and welcome.

If you've not already stumbled across it, my I recommend our excellent and knowledgeable comrade @Dal3D 's thread here, which contains some useful information and discussion relating to sound deadening (page 3 onwards).
 
There's already a thread on this here, so I'll merge the two.

Personally, I bought a large pack (80 sq ft/3.4 m2) of Noico Black sound deadening material as it was on sale (and black looks somewhat neater than the silver/grey foil) with the plan of installing it in the boot of the car and the door panels.

I've yet to install it in the doors, as the weather has not been favourable recently, and I will be doing the Focal speakers at the same time, but I've already noticed a vast improvement to noises coming out of the rear of the car on rough road surfaces.

My advice would be to scope out how much material you want to add and where first, and not to overbuy it, as it adds weight to the car (however insignificant it may be). It also helps to get an aftermarket exhaust and disable the sound generator if you want to hear the real car whilst driving it.

I also wouldn't buy Noico (or Kilmat) again on principle, as I didn't realise both were made in Russia. Dodo Mat seems to be a UK-based company and provides their sound-proofing material in neatly cut hex sheets. WIth a discount code, you can get 20 sq ft (which should be plenty for limited sound deadening) for £30 from here (this is the shop that also had the Focal speakers on offer for arond £135).
 
beorg said:
There's already a thread on this here, so I'll merge the two.

Personally, I bought a large pack (80 sq ft/3.4 m2) of Noico Black sound deadening material as it was on sale (and black looks somewhat neater than the silver/grey foil) with the plan of installing it in the boot of the car and the door panels.

I've yet to install it in the doors, as the weather has not been favourable recently, and I will be doing the Focal speakers at the same time, but I've already noticed a vast improvement to noises coming out of the rear of the car on rough road surfaces.

My advice would be to scope out how much material you want to add and where first, and not to overbuy it, as it adds weight to the car (however insignificant it may be). It also helps to get an aftermarket exhaust and disable the sound generator if you want to hear the real car whilst driving it.

I also wouldn't buy Noico (or Kilmat) again on principle, as I didn't realise both were made in Russia. Dodo Mat seems to be a UK-based company and provides their sound-proofing material in neatly cut hex sheets. WIth a discount code, you can get 20 sq ft (which should be plenty for limited sound deadening) for £30 from here (this is the shop that also had the Focal speakers on offer for arond £135).
Click to expand...
If I’d known I wouldn’t have bought Kilma. Good intel, thank you
 
can anyone recommend a sound deadening [anti-vibration] solution for the engine bay/bonnet?

Lots of thread comment about strut braces, strut brace damping etc. but I’m wondering if some front-end sound deadening would be a better place to start…
 
I did notice over the course of the weekend that the car seems very sensitive to road surfaces. Some stretches of tarmac seem to generate a much higher level of low frequency ambient noise than others. Other cars I don’t think I notice this as much other than the change provoked by going from tarmac to concrete.
 
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