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Like others, I decided to see what could be done to reduce road noise in the cabin. Following the lead of some previous posts, I decided to try some Dynamat in the rear wheel wells and in the doors.
What I intended to do, but did not (sorry) was take some sound level measurements before and after.
Starting with the rear wheel wells, here is the leading fender liner on the left side with the wheel off.
The liner is held on with some 10mm plastic nuts and T25 screws. Undo these and twist the liner out. This reveals the sheet metal between the fender well and the car interior. Note that the undercoat schutz mostly covers areas exposed around the outisde of the plastic liner. Tapping on the "clean" areas revealed a tinny sound, and I decided to cover these with Dynamat.
I made some paper templates with some trial and error, includind holes for the studs that mount the plastic liner.
The Dynamat is easy to cut with heavy duty scissors, and the adhesive seems very sticky, especially after pressing into place. I cleaned the sheet metal with solvent and really tried to work the edges of the Dynamat pieces to stick them well.
I added some scrap pieces to the hidden side of the plastic fender liner just to dampen sound transmission.
On the right side, the shapes are the same, but some of the studs are in different locations.
And similar scraps on the right plastic liner.
For the doors, I followed instructions posted elsewhere to remove the outer door panel. This is among the easier panels I have removed: popping out 4 plastic covers, unscrewing 4 torx bolts, and then pulling upward on the panel (followed by undoing an electrical plug and the cable end for the inner door release lever).
With the outer panel off, here is the view of the inner panel.
And here is the side air bag (inflator end) mounted. One electrical connector and 3 bolts hold it on.
And the airbag assembly removed.
Here is the door control module, with some sticky back foam covering the connectors, and with the connectors removed. Once disconnected, the module pops out.
Here's the inner panel ready for removal. The white plastic rivets are easily undone and removed by pulling on the center button. The rivets are also easily reused.
Once all the rivets are out, the panel comes off, pulling against some weak adhesive. The latch release cable tucks through by pushing out the rubber grommet. I decided not to undo all the cables for speakers, etc. There is enough slack to rotate the panel down after popping out the tabs that hold the skinny rear wire bundle.
I cut a long section of Dynamat for the upper part of the door skin, above the collision beam. I found the door skin to also sound very loud and tinny when tapping on the outside.
And a narrower piece fills in the lower part of the door skin.
The right side is exactly the same.
So, was it worth the effort? I can only claim a noticable subjective improvement. And yesterday, without any knowledge of what I did, my wife told me the car is quieter.
Thanks for the time taken to post this project, really appreciated. Did you consider the front fenders too or has that been regarded as not a serious noise contribution, from your reading?
Thanks for the time taken to post this project, really appreciated. Did you consider the front fenders too or has that been regarded as not a serious noise contribution, from your reading?
I did not target the front wheel wells since to me most of the road noise seems to come from behind the front seats. I may have to think about what is happening in front.
Excellent post. I too would like to make the car quieter; however, I am not brave enough yet to go about disassembling it in order to put the dynamat in. How many hours did your project take?
Excellent post. I too would like to make the car quieter; however, I am not brave enough yet to go about disassembling it in order to put the dynamat in. How many hours did your project take?
I would guess I spent about 3 hours on the rear wheel wells, and another 2 on the doors.
That's a lot of work, congrats for your bravery around those side airbag devices!
You may need more coverage on the rear fender lines, such as a double layer. I find most the road noise comes from the rear wheel wells on my 991 Cab.
Here's a photo of what Aston Martin does the rear wheel liners of the Vantage. I had one of these and while I was in there replacing a component and had the inner liners off I took it for a drive - the noise level was significant without them installed. You can see its pretty extensive.
The car isn’t that loud unless you’re used to luxury coaches i mean cars.
I tried this in my last boxster except the brand was second skin (dynomat is over priced garbage). Lots of effort and no tangible results. I thought you’d measure before and after? Saying your wife thought it was quieter isn’t exactly quantifiable.
Placing that stuff in the wrong area designed to dissipate hea will you cause weirdness requiring the engine compartment fans to come on excessively. The padding traps heat in and your interior gets more cooked in steamy park lots.
Sorry but that stuff doesn’t really cut down on road noise like you were led to believe. You need a different foam-like substance for that that. And a lot of it.
Its not possible to get rid of those massive tires’ roar with thin heavy padding designed to reduce vibration via increased mass/weight. You’re best off getting a different set of tires known to be less noisy, often simplier tread design. Snow or rain tires tend to be quieter.
06-21-2018, 12:13 AM
991 Noise Insulation
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