Butyl Mat - Sound Deadner install and RESULTS

Luisv

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A bit of background. A couple of months back, I took out the rear can on the GTS and replaced it with some pipe with an X-Pipe in the center. Exhaust note improved dramatically and I am very happy with the mod. It did get a bit too loud in the cabin and I wanted to attenuate it a bit. I have a drone that is not that bad, but I did want to tone it down a touch.

I posted a question about Vinyl Butyl mat or sound deadner (Dynamat, Hushmat, BoomMat, Second Skin, ect) to see if anybody had done it and what the difference was. The general consensus was "It will do nothing" and "The only way you will be happy is with a Corsa". The link is here.

http://forums.viperclub.org/threads...or-barrier...-Exhaust-drone-and-noise-control.

OK... I went ahead and did it. So you don't have to read on to the end or scroll there.... It made a very noticeable difference in the cabin. Since I prefer to give measures and not just my opinion, I measured the noise level in the cabin behind the drivers seat on the deck. There was a drop of about 8 to 10 dB at cruise (from about 104 dB). At the peak, under acceleration, at about 2700 RPM, the drop in sound level is less at about 4 dB. That is a significant decrease in the sound level. In addition to that, the drone becomes more attenuated. Since the mat removes vibration, the "sub-woofer effect" of the spare tire area is GREATLY reduced since the ability to vibrate is eliminated. I am not saying the drone is gone 100%... but it brings it to what I wanted... acceptable. If I want to make it even more quite I can go with a mass loaded vinyl product that will **** more sound, but I'll see what I feel like in a while.

Now onto the install....

I went with Hushmat. Basically it is the best adhering mat out there and from a performance point of view, it is as good or better than everything else out there. I bought a couple of bulk packs to keep the cost down. Since I am in the midst of a resto-mod on a 1977 Corvette, I will use the rest there. Took advantage of the project to lower the cost of the mat. As you will see I went with black to make sure it was not an eye sore if any bit was exposed.

The installation is not rocket science. It is quite simple and straight forward. Just have the right tools and you'll be golden. The only thing I will say is that it is not a comfortable job. You will spend a great deal of time over the rear of the car with your head in the trunk. While not a problem for a 30 minute install, it is a problem and tiring when in there for 2 or 3 hours which is how long it took. Be prepared, take breaks, let the blood run back down from your head.... :rolaugh:

So I decided to go with just the rear area. I will likely do the rest of the car (seating area) at a later time. For now though... the back was what I did. The process is simple to remove the rear carpeting. I removed spare tire, tool kit and all the plastic trim around the trunk area first. Only tricky part to that is the glass has to be held up while you remove the side panels. One piston will not hold up the glass so I had a buddy hold the glass for a second while I took the pistons off (one at a time) and removed the panels. Once the trim is out, simply remove the carpet covering the rear speakers and spare tire area first. Note here. The carpet sides are held in with some pegs on the side vents. They hold through the netting on each side. Be careful not to break those pins. Once that is out, the upper area comes off as easily. You will need to remove the radio amp and remove the bracket bolts. I left the bracket there as you can work around it and don't have to go through the trouble of removing the fuse panel. Once that is lose, you can remove the upper carpet. There are no fasteners holding the carpets down. You are left with the following

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Yes the rear speakers are dead... I know... they have been replaced already with a pair of Kicker Subs.

Once you have all the area free of carpeting, you can clean it up. I simply vacuumed the area and then cleaned the remaining fine dust with a moist rag. No need to use any solvents or alcohol with the Hushmat. Other vary, so make sure you look into what they recommend. Once clean you can start laying down the material.

On the laying of the materials.... The general idea is to lay the largest areas you can first. Then move the to smaller pieces that require a bit more cutting to make them fit. For example, the obvious big piece is around the "cylinder" of the trunk. It is flat (no grooves, bumps, etc) I did that with two full size sheets (for the Hushmat in bulk packs that is approx 2' x 1' ) to cover the top and then I cut two strips (2' long) to do the bottom section of the cylinder. From there the lower section of the spare tire area has one more sheet. You can see these in the shot below.

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Applying or sticking it down is easy in the flat areas. Once you get into groves and the like, it becomes more complex. What I did was to take the piece I was going to lay down and, before removing the backing, lay it into the area I was going to work. I would work into the groves (more or less) and bends getting the sheet, more or less, into the shape I needed. I then would remove the backing and apply as I went. I used a combination of a roller and my fingers to get the mat to stick and conform to the shape I needed. You can see in the shot above, I worked into the grooves in the floor of the trunk. You'll also see how I did it to the rest of the area in the rest of the photos.

Cutting the panels to shape. I did this one of two ways. First and the obvious is to lay the panel down in the area you are looking to apply it. Then mark where the cuts are going to be. At that point cut with you choice of scissors (which work fine so long as you are willing to toss them later) or a box cutter. I used both depending on how detailed the contour was. The other way to make the shapes is to use a sheet of paper to mock up the panel and then cut it out. This works well for smaller panels and areas that are tighter. For example, the to areas to each side where the trunk vents are. I also used this method when I had holes to cut to allow bolts and belts to go through. For example under the amp bracket.

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One area that I took my time on was the area in the trunk where the tail light bolt access. I wanted to make it as clean as possible leaving a way to get the bolts out and using the stock plugs. What I did was remove the rubber plugs first. Then I laid the panel in place and pressing in the indentations I could cut out for each hole. I then cut each hole as cleanly as I could against the edge with the box cutter. Once done, I simply pushed the plugs back into place.

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Here it is with the plugs back in place. You can see the indentations of the holes I have left to cut. It works perfectly as the mat itself is very thin and the plug will still grab fine.

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Luisv

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Re: Vinyl Butyl Mat - Sound Deadner install and RESULTS

I continue on moving to smaller and smaller areas and panels as I go. I try to keep the overlap to less than 1/4" as I go. One tip I do have is that you keep all the scraps as you go. As you move to smaller parts, you will start using the scraps you have. Small traiangles, strips and curves are useful in the tight areas. I covered as much of the area as I could, inclduing corners and indentaions that were not exposed to the exterior. The idea is to eliminate vibration. Any covered part will vibrate less. Here are some more shots as I moved forward.

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This is the **** created by the fuel fill neck. I went all the way around to the front side (facing the passenger seat back) so as to continue from there when I do the seating area of the cabin in the future.

To make my lie easier, note that I cut the circle out in the center of the upper deck. This is the access to the fuel sender (I assume) so I decided to leave the gap so as to be able to get it off should I need to.

Below is the shot of the drivers side rear vent area. Here you get a good look at the tail light access covers I cut out and put the rubber grommets into again.

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A bit further but still some small corners left on this side.

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Speaker boxes covered... (again, yes, the speakers are dead and have already been replaced). Here you can see what I did for the area around the license plate braket. I did not go nuts there. I covered the area a bit more and added a couple of strips to the black frame, but that's it.

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The finished trunk.

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In the end, I covered just about the whole area with some very small exceptions. The reason is that these pads eliminate vibration, heat transfer and sound, to a smaller degree. They don't need to be applied to the entire area to be effective in the vibration elimination. However, once I am there, I'll do it all. You will not save a ton of money doing only 60% or 70% of the surface area. As a heat shield, it works very well and, obviously, better if covered 100%.

As I mentioned at the top... the net result is a drop of about 8 to 10 dB at cruising RPM and about 4 or 5 dB under acceleration and peak volume. While it does not make the interior as quiet as a luxury sedan, it does make a significant and percieveable difference. In my opinion, worth the effort.

As for the work involved. It is not difficult in terms of skill. It does, however, get you tired. The positions, bending in an around areas, pushing in the product into the cracks ect are not easy after a few hours...I'm not 20 anymore... so at least for me, I was beat after the three hours of contortion... :crazy2:.... but the net result is worth it.
 

Bugman Jeff

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Great write up, it's nice to see some actual numbers on how effective it is. Up until recently, I built kit cars for a living and the difference sound dampner makes on a fiberglass body is amazing. Once I talked my boss into trying it, we never looked back. We used Damplifier brand, but they all work pretty well.
 

ksgts

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Great write up, Im getting my whole car done. Pretty sure that should make a huge difference inside, because my exhaust is really loud. Plus should make the new sound system sound amazing!!!
 

Tail lights

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Great write-up, and excellent information. Do you have any idea how much weight was added to the trunk area?
 
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Luisv

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Great write-up, and excellent information. Do you have any idea how much weight was added to the trunk area?

I used about 14 sheets. They are about 1 lb per sheet. Figure 14 lbs added. I lost more with the removal of the spare that has not gone back in. I may put it in there with poly fill all inside. Might improve the sound deadning... lol
 
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Luisv

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Great write up, it's nice to see some actual numbers on how effective it is. Up until recently, I built kit cars for a living and the difference sound dampner makes on a fiberglass body is amazing. Once I talked my boss into trying it, we never looked back. We used Damplifier brand, but they all work pretty well.

Thanks! I've heard the same. On the Viper I am looking to add it to the seating area as well. We are re-doing a Vette and it's going everywhere. On the Vette we are also adding mass loaded vinyl as that will have an open exhaust (essentially) with the side pipes so I am sure it will need it.

Great write up, Im getting my whole car done. Pretty sure that should make a huge difference inside, because my exhaust is really loud. Plus should make the new sound system sound amazing!!!

I must say the sound system in the Viper is not "perfect" but with the added rear speakers and the Hushmat, it sounds a great deal better than it used to!
 

Bugman Jeff

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Thanks! I've heard the same. On the Viper I am looking to add it to the seating area as well. We are re-doing a Vette and it's going everywhere. On the Vette we are also adding mass loaded vinyl as that will have an open exhaust (essentially) with the side pipes so I am sure it will need it.

I've used Second Skin's Luxery Liner Pro before with good results. It's pretty nice to work with, although it's heavy(It is mass loaded after all :rolaugh: ) Slightly off topic, but on my '73 Vette, I built my own sidepipe mufflers with a pair of THESE in each side. STS makes a similar muffler in stainless too. They quiet it down to a slightly more reasonable level without really changing the way it sounds and don't add to much restriction.
 
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Luisv

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I've used Second Skin's Luxery Liner Pro before with good results. It's pretty nice to work with, although it's heavy(It is mass loaded after all :rolaugh: ) Slightly off topic, but on my '73 Vette, I built my own sidepipe mufflers with a pair of THESE in each side. STS makes a similar muffler in stainless too. They quiet it down to a slightly more reasonable level without really changing the way it sounds and don't add to much restriction.

We went with the ****** sidepipes and have the spiral baffles in there as well.... Have not run the engine yet though to know how loud. Just assuming it will be.

Thanks for the info though! Good to know they work as advertised!
 

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