bogus wrote:
I have used frost king duct insulation with moderate success.

Another option is truck bed liner.

Work with the doors and the rear cabin area. Those are the real noise factories.

The best fix for exhaust is converting to Corsa! Not much will kill that resonance.

Matatk wrote:
There is a vendor who sells a precut sound deadener package for the whole car. His screenname is something like crazy cowboy. I'll find the info and post it later.

Matatk wrote:
Two sources:

http://www.exoticvette.com/insulation%20c4.htm

OR

http://www.corvettemods.com/C4-84-96- ... Complete-Kits_p_5565.html

I have zero experience with either kit so I can't comment. You might have to do a little homework. Maybe you can be our guinea pig

Matthew

-=Jeff=- wrote:
I am not sure the CC kit will cut down exhaust noise.. it might a bit for road noise, but in my ZR-1 I replaced all the Jute with the CC kit. the best for road noise will be dynamat or similar installed in the car.

I did the CC kit because of the foil and how it is suppose to deter heat, but I have not really seen an improvement, but again, I have nothing to base it off of, I replaced all the jute before I drove the Z for the first time

Scott7 wrote:
Quote:

Matatk wrote:
Two sources:

http://www.exoticvette.com/insulation%20c4.htm

OR

http://www.corvettemods.com/C4-84-96- ... Complete-Kits_p_5565.html

Matthew

I’m sure you could use a little time off and would like to come to colorful Colorado and help me with this little effort

I’ve also been looking at this double coverage Mid America Motorworks offering:

Scott

BillH wrote:
Quote:

Scott7 wrote:
Quote:

Matatk wrote:
Two sources:

http://www.exoticvette.com/insulation%20c4.htm

OR

http://www.corvettemods.com/C4-84-96- ... Complete-Kits_p_5565.html

Matthew

I’m sure you could use a little time off and would like to come to colorful Colorado and help me with this little effort

I’ve also been looking at this double coverage Mid America Motorworks offering:

Scott

I'd come over to colorful Colorado, I spent almost 3 years there racing motorcycles, er, going to collage.

The vettemod kit is worthless, no foil.

The other 2 kits look pretty good.

One of my jobs at Ingersoll-Rand was "sound control engineer" trying to quiet down construction equipment at a time when no one else was doing it, - not easy.

I did use close cell foam with doublesided foil in the engine compartments, it worked well on higher frequencies, so I like these kits for some of the road/wind noise.

I think you have to separate exhaust noise/resonance from the road noise. Exhaust is at lower frequencies and an exhaust system also vibrates thus the resonance.
And I agree that the rear of a C4 underneath the car has a lot of spaces that will act like a base speaker cabinet.
So, if you want to keep the current exhaust system, the only thing you can do is change the mass of some of those panels so that they vibrate at a different frequency - the bed liner Andy mentioned or maybe undercoating.
Or change to Corsa, their engineers must a boatload of time working on the resonance thing.

The exhaust thing would take a lot of experimenting.

Your custom rear valance may be contributing somewhat, it would be interesting to pull it off and see if anything chances.

Scott7 wrote:

Just let know when you’re arriving I’ll get the room ready . Things probably haven’t changed all that much, although there are a few more brew houses to explore. Where’d you go, Ft. Collins, Boulder?

CentralCoaster wrote:
Just remember, fluffy insulation dampens higher pitched noise, like white noise, wind noise, etc. The factory carpet padding does this well.

The denser insulation dampens out lower frequencies, bass, maybe some of the exhaust resonance. It doesn't require as much thickness of it to get the same mass as the fluffy stuff. Plus 1/4" of it would really add weight.

I put 2 layers wannabe dynamat in the front half of my car, kinda wish I hadn't. I think the seller called if fatmat. It basically added 10 lb to the front half of the car, minor carpet/trim fitment interference from added thickness, and it will never come back out without a massive mess. Results are dubious. I believe the product is actually called peel n seal, used for waterproofing shower membranes. It is a thick tarry film on a roll with foil covering.

I think the doors are a big source of noise. There is a product that goes inside the door panels I might try, for various other reasons, including quieting any minor rattles from all the stuff in the doors.

And I assume you're running the fiberglass top with headliner, not the ez bake top.

CentralCoaster wrote:
I did not do the back at the time because I didn't have it apart. I don't recall if I did the back behind the seats.

The back though is probably a huge source of noise. I can even hear my ring & pinion gears. (That's a whole nother mess why those are noisy), but yeah, I might have a different opinion if I didn't have just half of it done.