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Discussion Starter · #1 · (Edited)
To help cut down on road noise and some of the drone from my borla, I decided to dynamat the rear area of my CS. I decided on 3 areas to cover: the cabin wall behind the seats, the engine cover, and the rear trunk area.

Researching dynamat, it was suggested that two layers be applied: a bottom layer of dynamat extreme, and a top of dynaliner. I found multiple vendors for both on amazon.

Description:

Dynamat extreme is a thick foil w/ a backing of a black adhesive compound -- the overall thickness is about 2 - 3 mm. This is advertised as both a sound-deadener and a thermal barrier. It is not difficult to handle, but it doesn't shift easily w/o creasing and requires some work to make it conform to the surface it's being applied to. There is little stretch in the top aluminium layer. It has a paper backing covering the black adhesive.

It's available in multiple sizes - I used their 'trunk pack' as I thought the sheet size of 18" wide would work well in the cayman. this pack has 5 sheets for 20 square feet. I used four.

Dynaliner comes in 1/8", 1/4" and 1/2" thicknesses and is a close-cell foam w/ a very nice adhesive on one side. it is very easy to work with and conforms well to the surface being applied to. I bought 2 12-sq. foot sheets of the 1/4" thick stuff - each sheet was 32" x 54", and ended up using 1-1/2.

Dynamat emphasized that it's important to get as much of the materials to adhere to where they're being stuck -- for maximum sound deadening. They offer a roller on a handle. I regret not buying theirs as the cheapie I bought broke 2/3rds of the way thru the project.

To repeat - this stuff isn't just pressed gently into place -- it's rolled w/ a significant amount of force. The dynamat takes more work to install than the dynaliner.

I started on the wall behind the seats -- removed the carpets and the serpentine access hatch. I used this as a template for cutting the cover dynamat and dynaliner.

I'm not going to do a detailed how-to, -- if you have questions, ask ... The job I ended up with was good enough for me, given that it would all be covered w/ carpet ... not a car-show quality installation but I'm happy.

here are a few photos:

The area behind the seats - w/ dynamat installed:


A closeup of the same:


Dynaliner applied to most of the rear wall - I finished the job w/ scraps:


The dynamat'd engine cover - note the hole cut for the emissions system diagram:


The bare rear trunk area -- my biggest candidate for reducing exhaust drone:


the same w/ dynamat:


And the rear trunk in dynaliner - left corner detail:


I'll be taking a 400 mile drive on Thursday and will have my impressions then. Very first thought when moving the car back into the garage is of a nice noise reduction.
 

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Total cost and hours spent?? This seems to be a good noise/drone abatement solution. Most of my exhaust noise seems to be behind in engine in the trunk area.
 

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Discussion Starter · #3 ·
Total cost and hours spent?? This seems to be a good noise/drone abatement solution. Most of my exhaust noise seems to be behind in engine in the trunk area.
Less than $200 for the materials and maybe 3 afternoons.

Thanks !
 

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I was wonderin' just the other day why no one had tried this. I'll be curious to read the follow up review.
 

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Brilliant idea! Can't wait for the review.

Would you consider measuring the dB levels? Those could then be compared to cabins without the dynamat application. Not scientific I know, but it would be interesting to compare.

Thanks for the information!
 

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Discussion Starter · #10 · (Edited)
what does the dynamat you installed weigh?

did it quiet Borla drone?
I didn't weigh the dynamat, but it wasn't heavy. the dynamat, (area-for-area) weighs roughly what a vinyl floor tile weighs. sorry, best I can do.
The dynaliner is light.

I won't have results until Thursday -- I ran the engine once after the install was finished to put the car back into the garage. seemed quieter but I want to live w/ it for some miles.
 

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I was the one who did this and used a sound meter before and after. I did not do the area behind the seats but did do the area over the engine and the rear hatch. Seach on my name and you can find the results. Overall it helped a little on road noise but it was not a big improvement - not as big as I had hoped. The only thing I have found that reduces the drone of aftermarket exhaust is extending the exhaust tips.
 

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I was the one who did this and used a sound meter before and after. I did not do the area behind the seats but did do the area over the engine and the rear hatch. Seach on my name and you can find the results. Overall it helped a little on road noise but it was not a big improvement - not as big as I had hoped. The only thing I have found that reduces the drone of aftermarket exhaust is extending the exhaust tips.
I am very curious about your experience with reducing the drone of an aftermarket exhaust by extending the tips. Could you please elaborate?
 

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Pardon for butting in, but I believe that getting the exhaust sound as far away from the rear undercarriage on a Cayman as is cosmetically possible will reduce the acoustic coupling into the rear cabin area. Just a theory...
 

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It seems to me to greatly reduce the drone you have to create some turbulence in the tail pipe itself. At least this has been my experience.
 

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Discussion Starter · #20 · (Edited)
Plainsman. How about a report?
good reduction in higher frequencies, generally a quieter car on the road. Less impact to the drone - not much at all.

Next I'll remove the seats and carpet and dynamat farther forward. In terms of the borla drone, the floor really seems to vibrate.
 
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