Sound deadening in trunk
 

Hey! I really love having my back seats down but the exhaust drone and road noise is just too much. I didn’t realize the back seats played a large role in dampening the sound. I’m looking into putting some dynamat in my trunk to remove some of the noise (Not a majority cuz I like my loud car) but where would you guys recommend I cover mainly? Around the spare? On the lid? Wheel wells?

Dynamat (and the like) are sound dampeners (vibrations and resonances)
You need Acoustic Foam Panels if you want to quiet down external noises from passing into the cabin.

Sound dampeners need strategy placement to not need full coverage, if you know the right places a little goes a long ways.

Acoustic foam works best will full coverage as much as possible.

You know where most of the sound comes in from? I’d guess near the trunk lid but I’m not sure

Scroll way down the pictures

https://www.ft86club.com/forums/showthread.php?t=53511

I have pics on my build too. I did it all. Made quite a difference.

Before you add dampeners which also adds weight onto the panels, perhaps you can address some of the exhaust drone by dampening the exhaust pipe first. Treat it like any other wind musical instrument. If you put dampener/insulation on the exhaust pipes (mid & catback), the insulation material can absorb some of the pipe's vibrational frequencies & muffle the sound. When we wrapped DEI Form-A-Shield onto the mid pipe of the `19 TRD SE exhaust, the mid & high notes got muffled making the sound more on the bass side.

For the road noise, having underbody covers like Verus rear diffuser, Transmission Tunnel Cover, Differential/Suspension Cover, & the JDM Underbody Aero Covers help too as they reduce the drag that also creates such noise. You're also getting the benefits of increased downforce.

If, after doing the aforementioned, still doesn't give you the lower noise level that's suitable for you, then you can start adding dampeners to the body.

I have the JDM underbody covers and a rear diffuser. The voices in my head tell me they make a difference in aero but I haven't noticed any noise reduction. I'm hesitant to cover the drive shaft tunnel since that is the main route for air to exit the engine compartment. I don't know if anyone had engine temperature issues with these covers.

While the above seems true it also sounds much more expensive than sound dampening. From what I recall in another thread the guy added quite a lot of dampening/deadening (trunk, under rear seats, doors) and it only added ~20 lbs (which sounds about right compared to covering the whole car interior in the link Tcoat posted coming to 70 lbs)

If you want to reduce vibrations, resonances and clean up the overall sound quality of your sound system about 15lbs of dynamat strategically placed will go along ways. knowing the optimal places though is hard if you aren't some expert so most people just cover all surfaces which ends up being closer to 25-30lbs.

If you want to noticeably reduce the DB level in the cabin you will need probably at least 20+lbs of acoustic foam to make a difference, and most people will go a lot more.

Most people looking to reduce DB levels will also do dynamat at the same time. So you are really looking at a good 45+lbs depending on how you do it.

However most of this weight is on the rear half of the vehicle so the added weight penalty is minimized, and can be easily offset by removing trunk junk.

I've never had temperature problems from covering the transmission tunnel. But, then again, I live in Vancouver where the average temp in the summer is between 25-30C (77-86F).

If you think about it, air is still being circulated because of the driveshaft spinning, & hot air is also sucked out by low the pressure at when at speed.

Perhaps you don't notice it bec. you already have the JDM covers to begin with. When I had the underbody covered with Verus & JDM panels on my former FRS, which didn't come w/ JDM panels, I noticed some road noise reduction.

I was just speculating about the trans tunnel cover. I'm glad your experience has been good. I'd like to hear from someone in a warmer climate.



My car did not come with the JDM panels. As I said, I detected no sound difference after installation.

I have all the JDM panels as the car was bought from japan auctions and imported. I just wrapped the front pipe as it was radiating heat in the tunnel and heating the cabin.

After a good spirited drive when you touch the upholstery by the tunnel it is always very warm.

After the wrap it is much better, less heat.

The exhaust tone is slightly "bassier". I am still on stock axle back, the rest is catted(high flow)/resonated front pipe and and EL header (also wrapped).

*Edit.
I was able to get a better observation today. The exhaust sound has really calmed down a bit, feels more quiet than before. And some of the higher frequencies have toned down.
Too quiet.lol.

Need to get a nice axle back now. :)

A small observation from todays driving.

The cat in the front pipe was not wrapped, I didn't know if I should have.

That's the only thing that is radiating heat into the cabin.

Is It Alright to heat wrap a Catalyser ?

Thanks.