Sound deadening trunk

[eagleguy]

So, its seems that my new Pypes exhaust system with Race Pro mufflers resonates way more than I would like. Ironically, I also installed one of those nice trunk kits at the same time and think it might have added to my issue. By that I mean that the truck kit has crap for backing/insulation and was wondering if that has contributed to my woes as it is not as good as the OEM stuff I took out. Any ideas?

 

[Chuck Leeper]

Put a layer of fat Mat down, then the trunk kit...

 

[eagleguy]

Put a layer of fat Mat down, then the trunk kit...

Saw the stuff, thanks. Is there was something that I could just lay down without using adhesive?

 

[hawkfan]

Saw the stuff, thanks. Is there was something that I could just lay down without using adhesive?

Mass loaded vinyl and closed cell foam. It's heavy though. But you shouldn't be getting much noise from your trunk unless you are missing the sound barrier behind the rear seat.

 

[RmvBfrFlght]

+1 on the back seat sound barrier. Also, give the exhaust some time to carbon up. It really makes a difference and the sound becomes more mellow.

RemoveBeforeFlight

 

[eagleguy]

Put a layer of fat Mat down, then the trunk kit...

Fatmat? Exhaust sound is actually getting worse. What do you guys mean about the insulation behind the back seat? When I installed the cross braces I did not see anything that looked like insulation. When I install the trunk kit which is the same as Kirbans it came with a carpeted plate that covered the crossbars. Since the new exhaust install I get this nasty drone at 45-55 or when the trans downshifts coming from the rear of the car. When I threw some carpeting I had laying around on top of the trunk kit it did seem to make somewhat a difference. Pypes told me I should have no such issues with the mufflers I have but I do.

 

[hawkfan]

Saw the stuff, thanks. Is there was something that I could just lay down without using adhesive?

Mass loaded vinyl and closed cell foam. It's heavy though. But you shouldn't be getting much noise from your trunk unless you are missing the sound barrier behind the rear seat.

Fatmat? Exhaust sound is actually getting worse. What do you guys mean about the insulation behind the back seat? When I installed the cross braces I did not see anything that looked like insulation. When I install the trunk kit which is the same as Kirbans it came with a carpeted plate that covered the crossbars. Since the new exhaust install I get this nasty drone at 45-55 or when the trans downshifts coming from the rear of the car. When I threw some carpeting I had laying around on top of the trunk kit it did seem to make somewhat a difference. Pypes told me I should have no such issues with the mufflers I have but I do.

There's sound insulation that hangs on 3 hooks behind the back seat. The tar on the insulation cracks and falls off with age, so the previous owner probably took it out. It's important because it separates the trunk from the passenger compartment and covers the wheel wells. There's another piece of that same material under the bottom back seat cushion. Without those pieces or some kind of barrier in those spots, any road or exhaust noise can easily get into the cabin. Remember your mufflers are now practically under your rear seat.

 

[eagleguy]

Put a layer of fat Mat down, then the trunk kit...

Fatmat? Exhaust sound is actually getting worse. What do you guys mean about the insulation behind the back seat? When I installed the cross braces I did not see anything that looked like insulation. When I install the trunk kit which is the same as Kirbans it came with a carpeted plate that covered the crossbars. Since the new exhaust install I get this nasty drone at 45-55 or when the trans downshifts coming from the rear of the car. When I threw some carpeting I had laying around on top of the trunk kit it did seem to make somewhat a difference. Pypes told me I should have no such issues with the mufflers I have but I do.

Mass loaded vinyl and closed cell foam. It's heavy though. But you shouldn't be getting much noise from your trunk unless you are missing the sound barrier behind the rear seat.

There's sound insulation that hangs on 3 hooks behind the back seat. The tar on the insulation cracks and falls off with age, so the previous owner probably took it out. It's important because it separates the trunk from the passenger compartment and covers the wheel wells. There's another piece of that same material under the bottom back seat cushion. Without those pieces or some kind of barrier in those spots, any road or exhaust noise can easily get into the cabin. Remember your mufflers are now practically under your rear seat.

I have no such insulation.

 

[hawkfan]

I have no such insulation.

Okay then that's why you have drone. I used my deteriorated originals as templates to cut new ones out of mlv and ccf, I found them both online though. I tried the vendors here first but couldn't find anything. These were on Ebay.
http://www.ebay.com/itm/78-88-GM-A-...ubber-Backed-Jute-Sound-Deadner-/251973585923
http://www.ebay.com/itm/78-88-GM-A-G-Under-Rear-Seat-Insulation-Sound-Deadner-/331804803456

 

[RmvBfrFlght]

Dennis carries the under seat and behind seat insulation:

http://www.kirbanperformance.com/pr...UNDER+THE+REAR+SEAT+SOUND+DEADENER+#7656.html

http://www.kirbanperformance.com/product/97/SOUND+DEADENER+INSULATION+INNER+TRUNK+DIVIDER+#7098.html

Being the cheap SOB I am I used a floor mat cut to fit. This was for the behind the seat insulation. The floor mat is the ones seen at entrances of commercial buildings.

They are a heavy rubber mat with a short tough carpet bonded to them. Used what was left of the original insulation as a template to cut it to shape, cut three slices to hang it.

RemoveBeforeFlight

 

[hawkfan]

Dennis carries the under seat and behind seat insulation:

http://www.kirbanperformance.com/product/44229/REPRODUCTION+UNDER+THE+REAR+SEAT+SOUND+DEADENER+#7656.html

http://www.kirbanperformance.com/product/97/SOUND+DEADENER+INSULATION+INNER+TRUNK+DIVIDER+#7098.html

Being the cheap SOB I am I used a floor mat cut to fit. This was for the behind the seat insulation. The floor mat is the ones seen at entrances of commercial buildings.

They are a heavy rubber mat with a short tough carpet bonded to them. Used what was left of the original insulation as a template to cut it to shape, cut three slices to hang it.

RemoveBeforeFlight

Good find. They're actually cheaper from Kirban's.

 

[eagleguy]

I know this may be a stupid question but could the drone I am not supposed to have been caused by me adding extended SS tips to my system. The tips are 2.5 at the pipe and 3" on end at 9" long. I slid them back as far as the pipe mounting bracket would allow so they go over at least 6" of exhaust pipe.

 

[eagleguy]

Anyone ever try this stuff?

https://www.amazon.com/Car-Insulati...=1470440189&sr=8-8&keywords=Carinsulation.com

 

[eagleguy]

Double post!!!!!!!!!!!!!!

 

[eagleguy]

Insulated the trunk and still have the drone noise at 1800-2000 rpm. So much for research telling me the Pypes system with Race Pro mufflers had the least drone as its actually worse than the no name pitted unit I replaced!

 

[RmvBfrFlght]

I know this may be a stupid question but could the drone I am not supposed to have been caused by me adding extended SS tips to my system. The tips are 2.5 at the pipe and 3" on end at 9" long. I slid them back as far as the pipe mounting bracket would allow so they go over at least 6" of exhaust pipe.

They may, easy enough to remove them and try it.

RemoveBeforeFlight

 

[Turbo6Smackdown]

Lots of good information here. For all you guys that have experience in this thus far, would you say that the factory sound deadener is on par with this aftermarket stuff like the brown bread and dynamat & whatnot? Re-doing my interior and I love a quiet cabin...

 

[pmesfun]

I used dynamat extreme under the rear seat. The black tar stuff broke into hundreds of pieces when I pulled out the original insulation. I removed the remaining pieces off the insulation and reinstalled in the car. The car is much quieter.

Sent from my SAMSUNG-SM-G920A using Tapatalk

 

[1986 Buick GX1]

While testing cab roof liners in the quest for lower decibels for a major U.S. tractor manufacturer in the mid nineties I learned that the tar-like substance rejects sound and the foam-like stuff absorbs sound.
The one that worked the best had an 1/8" of foam on the outside, a 3/16" layer of heavy rubber tar-like stuff and 3/4" foam on the inside.
Most of the sound was kept out by the tar-like stuff and what made it through was absorbed by the foam.
It was still quite loud as it was in a 200hp, 500 lb/ft torque tractor.
The sound reduction is dependent on the weight and thickness allowed.

Just food for thought.

 

[SHADOWII]

Some where in the archives is an old discussion about the drone that was driving everyone batty. What I can remember from it was the purpose of the factory designed exhaust was to eliminate the drone. Which doesn't show up until we went from the stock to aftermarket. I went to a 3" exhaust and couldn't find anything to stop or neutralize the drone. I even tried a high dollar special foam/lead insulator to no avail, w/most of my driving speeds being between 45 and 60. I ended up driving either too slow or speeding!