I have a subwoofer under the strut bar in the hatch of my 05 350z. When dynamatting my trunk I found air vents in each corner which open directly into the rear bumper. So, despite dynamatting the trunk, these open holes allow air and sound into the bumper and cause it to rattle. Furthermore, they have flaps on them which allow air to exit the car but not enter, so during certain bass frequencies these flap (flutter, if you will) open and shut loudly. Does anyone know what these are for, and what the side effects are to sealing them off (or, secondly, removing the flaps to leave them permanently open)? I haven't been able to find anything on the internet about this, but I'll guess they do something with the air pressure or flow when the windows are open or maybe just with the vents/AC.

Thanks.

 

The flaps are there to encourage air flow through the cabin. Air enters in through the dash vents and exits though a pair of vents back there in the trunk. I'd be less concerned with air flow and more concerned about tininitis.

 

I also heard that those vents are for air pressure to exit the car when closing the doors.

 

Thanks, I suppose I'll just seal them off and see what happens. I'm apprehensive, however, since the manufacturer seems to have gone through some trouble to add them. I was hoping someone else had experience with this so I could save the effort of trial-and-error. I'm surprised more people haven't run into this... my sub isn't THAT extreme (500/1 JL to JL 10w6).

 

I filled mine with some glass... Its better this way... Masking or taping it will not solve your problem... Taking them off will make it even worse... With out a vent everytime you open a door the open vents will suck in dust in a month you would have accumulated at least 1 POUND of dust in your car... How do I know this... I have tried it and its the dust is not visible it stays under the plastic intetior... Cleaning is a pain, you cant just vacuum it needs to be wiped down!!!

Well I hope that helps... Just have it filled with bondo or fiberglass...

 

Thanks! The dust sounds terrible, so I'm glad I didn't try that! I figured I'd pull out the vents and cover the holes with two layers of dynamat since that's what I have available (I haven't done fiberglassing before). I should really get dynaplate... You've noticed no adverse affects from sealing them then?

 

I've had them sealed before. I noticed the trunk was much more difficult to slam shut. Whoever above mentioned about the airflow helping with door/trunk shutting was right on track (pressure).

 

And if the airbags ever deploy! Are you really sure you want to seal those things off?? I definately noticed the noise they made when I installed my stereo too but once everything is back together you can't hear them inside the car. Outside, yeah I guess they still rattle like crazy but I sure wouldn't seal them off. I was thinking of adding a layer of something on the inside to slow down the rush of air (because the flaps are so thin any air movement sets them off) but still let it breathe but decided not to waste my time.

This has been brought up a couple of times before. See previous posts

 

Well, I sealed them off. I've noticed no problems closing the doors or the trunk. I do notice somewhat less air coming in while driving with the windows open, which isn't such a bad thing. There's a little bit of turbulance but I'm not sure how it compares to before as I didn't really do a before-and-after. The inside sounds EXTREMELY clean now, and outside the car improved but not as much as I'd hoped. Obviously the flapping sound of the vents is gone, but the bumper still vibrates. I skimped a bit on the dynamat around the tail lights and I think all the pressure is now forced though there. Oh well.

I have some pics of the dynamat'ed trunk if anyone cares to see em... and if you need some advice or tips, let me know!

 

When you say it sounds extremely clean inside are you saying that you could previously hear the flapping from inside the car with all of the panels installed?? Glad you had some improvements without any negative effects yet.

 

Sorry, my comparison from inside the car with the panels on is after both dynamatting and sealing the vents. Also, since I didn't know about the vents ahead of time I wasn't listening for them. I wish I could be of more help.

 

Ah, I missed that. Before and after of ALL dynamat. I was just curious because I can't hear my flaps unless outside the car. Enjoy the improvements As bad as things can sound on the outside I guess just don't worry about it. I never listen to my system loud around where anybody can hear it anyway. There is only so much you can do. Be glad the inside sounds good!