Noise Reduction

SeaDweller · 09-25-2002, 05:17 PM

I know, I know, it's blasphemy, but I need some advice on reducing the noise in my SC. I don't know if my car is the same as everyone elses, but mine's just one step up from a VW sand rail that my brother used to own. For being nearly 25 years old, the car is incredibly tight (no rattles or squeaks), but the road noise is getting intolerable. To make matters worse, I have no suspension (it's so tight that it feels like the wheels are welded directly to the body). Cracks in the road sound like thunder, and even those little dividing line reflectors skip my CD player if I run over them!

I'm not overly concerned with weight, as this car is my daily driver, and I don't currently participate in track events or anything of that nature. Besides, I'm happy with the cars performance, and figure I could throw on some SSI's to offset any weight added by the noise reduction.

Has anyone used Dynamat material to reduce road noise? The floors seem to be the biggest culprit, but I'm thinking of "Dynamating" the door shells, floors, rear package shelf, and maybe a couple of other areas.

Also, regarding the suspension, I have the European version with huge torsion bars, it's lowered, and I have the big Fuchs which put a lot of rubber on the road. Is there any way to get a little more flexibility out of the suspension?

Thanks!!

RoninLB · 09-25-2002, 06:40 PM

I did a Dynamat/I used the expensive Dynamat choice..floors, tranny tunnel, rear lid, engine comp, doors..it helps w/higher frequencys. like tranny gear noise..and the muffler does sound cleaner, IMO..The sardine can sound is gone, and the door closing sound is much "heavier" sound wise..kinda like heavy duty ...I have 22/27 springs, stock sway bars, Bilsteins, Welt. bushings, and S-03.. and road noise is no problem..I would suggest removing your door windows/easy, and do the doors and floor to start...I could do the front lid, but never got around to it..what happens, IMHO, is "sympathetic harmonics"..where your doors and floors act like speakers for road noise..besides any vibration which does the same thing to doors and floor..not an expert on this stuff.............Ron

911pcars · 09-25-2002, 06:45 PM

Chassis vibration and noise can be wearing after awhile, especially on marginal roads. Have you considered trading in your huge torsion bars for some merely large ones? You don't say what size, but it sounds like something close to 30mm rears? Are your sway bars really huge too?

Some tire tread patterns create more road noise as well. If you've got a friend with similar sized, but different brand tires, you could try a temporary swap.

I sound like a JC Whitney salesperson when I suggest using their version of Dynamat instead of the real thing. It's basically the same and you get a large 32x54" piece of material for about $30 instead of $100. Other than the floor, I suggest only using strips of it on any flat surface that might transmit vibration. It's relatively heavy, so don't go overboard with it.

Sherwood Lee
http://members.rennlist.org/911pcars

RoninLB · 09-25-2002, 07:02 PM

there is some stuff called "BrownBread" that is in the same class as the expensive model Dynamat..and costs much much less than Dynamat..........Ron

Ove · 09-26-2002, 09:15 AM

I would go for a liquid product called Noise Killer. Much lighter, and easy to work with. It sprays on, and can be removed with water while still wet if you make a mistake. See my reply here:

[Heresy] How To Make 911 Quieter