Hey fellaz,

I am about to put SLP loudmouth pipes on as well as my sub back in the trunk of my convertible. I have heard that dynamat and other sound dampening products do not work well with the fiberglass. Could anyone weigh in that has heard this or has success with dynamat in their vette?

Thanks...

 

it doesn't work as well as it would in a metal car because fiberglass doesn't resonate as much to begin with. i have straight pipes in my car and high flow cats and the sound deadener didn't make it that much quieter but it did reduce the road noise considerably.

 

with high flow cats do you have any prob's passing inspection?

 

i'll let you know when that time comes :-) if it's the sniffer test that you're worried about then you can do the good ol denatured alchohol trick i used to do with my rx-7 a 50/50 mix with gas after you heat up the cats and you should pass w/o a problem

 

i just recently did the rear cargo area with dynamat xtreme and it made a huge difference -- HUGE --

I have the B&B bullets...

 

you can also look into edead by elemental designs. they make some really good stuff and doesnt cost as much as the other stuff from what i remember.

 

Try a liquid damper, followed by a closed cell foam noise barrier.

I've done the liquid damper, still deciding on noise barrier.





The liquid is nice because you can concentrate your efforts on the bad areas (large flat surfaces, such as the back wall that will resonate terribly.)

This damper I've applied is about 3x thicker, for example, on the back wall than it is on the corrugated floor. (2 coats vs 6 coats)

 

it helps dampen a lot of interior squeeks too!

 

I plan on Closed Cell foam in the back of my C4 to replace the padding for the carpet that is there. I hope it will cut out some resonance..

 

For the C5 and C6 people make packages for that ... pre-cut..

 

if its more than $2 a square foot, forget it.

 

Here's a write up I did on my install a while ago:

I just got done installing RAAM matting sound insulation in the car and then went out for a drive. Here's info and a comparison on the stuff I used.

http://www.sounddeadenershowdown.com/

I can't believe what a huge improvement it is in the whole driving experience. The stock stereo sounds way, way better. I can still hear the motor and exhaust during high rpm driving, but it's from outside, not inside.

I did the trunk, rear panel, side panels, wheel wells, behind the seats, outside and inside door panels, and the interior door panels. It did take me a few hours. I also installed my Brey Krause bar and Simpson belts at the same time.

I highly recommend this mod. You will love your car even more!

Once I got the interior pieces, door panels, and seats out it went pretty fast. I hadn't taken any of the stuff out of the car before so it took me a while being careful not to break any tabs. I'm always a little nervous when it comes to the pry and pull work.

I laid a piece of plywood on the ground and used a T-square and box cutter. I did not exact fit the pieces, some I just cut 1"-2" strips, some I measured the area then cut larger sections. If you have someone to help it would go a lot faster. One person to stay at the car measuring and installing, and one person to cut and hand material.

Reinstalling everything was pretty easy, except for my screw ups. I had to remove the passenger door panel three times, first I forgot to install the plastic piece that covers the big hole, then when I tested the stereo I found I had forgotten to hook up the speakers in that door. Now I'm nearly an expert and can take off and install a door panel in about 2 minutes.

The stuff I read said that you don't have to completely cover the areas. The idea is to dampen the vibrations, just like putting your finger on anything that is vibrating. As I was installing the stuff I would test a covered area against a stock panel. I just tapped with my fingers. The stock panels sounded like a high pitch drum, the treated panels just thud.

Now that it's done I had to re-adjust the stereo, the treble is turned down and the bass is turned up. It sounds like a new upgraded stereo. Also my side mirrors don't vibrate as much.

Before I installed the sound deadener my buddy and I took readings with his sound meter under different driving conditions. Not super scientific, just trying to see how much difference there is.

Here are my sound test results before and after the sound insulation. The tests were performed a few days apart with the windows up, on the same roads/freeway. My buddy held his sound meter in front of him at about chest level. The before numbers are for my stock car with a partition installed. The after numbers are with sound insulation and partition.

Before / After

Parked at idle: 85-86 db / 83 db

30 mph in 4th gear 92 db / 87 db

80 mph in 4th gear 103 db / 97 db

80 mph in 6th gear 101-102 db / 96 db

Full throttle accel 2nd/3rd gear 104 db / 104 db

This number came out wierd, but here it is;

60 mph at idle in neutral 87 db / 92 db

I attribute this reverse result to going the other way on the freeway on rain grooved concrete vs smooth pavement. This is also a good indication of how loud the car is from tire noise on the rain grooved concrete, as if any Z06 driver didn't already know it's a lot louder on concrete.

Not only does the stereo sound way better, now I can actually hear faint wind noise from outside the car at freeway speed. You can see that under acceleration it's pretty much the same, the exhaust sound dominates from the back.

Let me just say that 5 db's is a lot. My buddy noticed the obvious difference in the car as soon as he got in. My wife likes it a lot better too. And if you knew my wife you'd know that keeping her happy means my life is much more pleasant. When she's happy it allows me more freedom with the dollars for future mods.

For people concerned about the weight, I estimate 20-24 lbs is the maximum weight added, based on how much my buddy used before he gave me the roll. I also installed the euro headlights last night – which added 3 more pounds compared to stock plastic lights. I don't know how much the Brey Krause bar and Simpson belts weighed, but they're also in there now.

Dog

 

I just put 4 layers of Second Skin Audio Damplifier in my 92 convertible (rear cargo and floorboards). I have 3 inch Tri-Flows and a 383 Golen motor. The resonance was terrible before, but now it is MUCH quieter. This mod does help. The car will never be silent, but it is now bearable whereas before it was not.

I can recommend the Damplifier from Second Skin, however, they shipped me the regular product (normally $160) when I ordered the Pro product and paid them $300. Since the product came in a nondescript brown bulk box, I could only tell which product I actually got by checking the dimensions of the sheets myself. Be careful when ordering, but the product is good, and cheaper than Dynamat.

 

If you can afford the Dynamat, don't settle for anything less. It's proven itself time and time again. Use Dynamat Extreme

 

Yes, Dynamat has proven to be a great damper. Just like most of the 'cheap' ones have proven to be as good or better

I will respectfully disagree with VinceC5, and say don't be a brand zombie.

 

it's ok to disagree, as long as you did it respectfully.

And yes, it's all about the brand....

 

here's mine..

http://home.comcast.net/~mbenway/trip5_dynamat.htm

Did cut down on the noise quite a bit. But switching to non run flats cut down the noise almost as much.

 

To give you an idea what sort of noise reduction 3db is, to make your stereo 3dbs louder, you need to DOUBLE the power provided to a given driver or the system as a whole. So 3db is pretty significant.

I have a combination of Cowboys kit, Dynamat Extreme, and ED's liquid deadener in my car. Liquid in the front cabin and inner/outer door skins and Dynamat Extreme on the outer skins and in the rear with the sub and surrounding areas and Cowboy's kit throughout. Noticeable improvement.

I am actually going to go back in and do some more Dynamat or Raam, or maybe ED stuff in the next few weeks as I will be bringing the crossover point down in my midbass drivers and I already have a bit too much resonance in the doors now so it will just get worse.

Worthwhile time investment for sure, and you do not have to be a brand *****, no one product is vastly superior to the other. Do some research on weight/thickness per dollar and spend what you feel comfortable with getting it done.

Fej

 

Fej, since you've been through this before -

What areas of the car do you think would best benefit from a closed cell foam application?

From your post, it sounds like you can't put too much in the doors. That's what I hate about fiberglass door panels... I had TONS of deadening on my 86's doors, and they still had huge resonation problems. I ended up cutting 160hz almost completely in that car.

No deadening in my saab's steel door panels, and virtually no audible resonance.

Perhaps we should start a post "Corvette deadening problem areas"

or a Corvette Deadening faq...

I just ordered 50 square feet of edead mat, plus another bucket of edead v3 paint.

 

Mainly the areas where the interior bits are push in to fit (so most of them ) Places where the interior bit sits away from the panel that it is fixed to. Like in the z06 there is a panel that runs underneath the rear window that needed a nice taped in piece to make it fit snug and it has made a huge difference in rattle/vibration. The panels behind the doors near the rear speakers also need some attention, but I have yet to do them as I have a feeling it will take multiple layers to fill that space.

I have the closed cell basically throughout the interior in mine, but none on the doors. Have to be careful to not overdue the closed cell however as stuff starts getting tough to snap back into place when you get the carpet back down. I know I am going to do some more work on the doors, and I may end up throwing a bit of closed cell on the outside panels to get a better door panel fit.

Fej