Making a downpipe a little quieter - wrapping?
 

Hey guys-

Does wrapping a SS downpipe make it much quieter? The whine of the turbos is certainly cool, but it does get annoying on the highway with the windows up when you can still hear the primary loud and clear :-). If not, are there any other suggestions of ways to muffle the whine a bit, besides using a big ol' stock pre-cat?

I feel like an old man for asking this question... but when I put my windows up, I like it to be quiet :-).

Thanks!

Take care,
Shad

er...wrapping your dp is to lower temperatures radiated from your dp into the engine bay. It is not used to muffle sound. Also, the noise is from the turbos not your downpipe.

Any insulation you put on the exhaust will quiet it to some degree. I was quite suprised by the increase in noise when I went single, with the tubular exhaust manifold from the cast original. Not that I don't like it

Yes... I realize that exhaust wrap is primarily intended for temperatures.

Yes... I realize that it's the turbos that whine at 100,000rpm and not my downpipe.

However, I also realize that the stock cast iron downpipe did a good job of muffling the whine (and causing quite a restriction). And, I also realize that fiberglass is an okay sound insulation material. That's why I asked the question... not because I'm an idiot that doesn't understand that turbos whine and exhaust wrap is designed for thermal reasons :-).

Take care,
Shad

Did you by any chance do a before and after with the insulation, or just an after? Was there a notable difference?

Aye - the whine is a pleasant sound when I'm cruising along with the windows down enjoying the drive. It's just a little annoying when I'm on the highway going from point A to point B with the windows up <sigh>.

Take care,
Shad

The thin layer that is used for insulation may dull the sound a little but nothing significant. If you want it to be quieter you may have to wrap the downpipe several times to ensure a thick lay of fiberglass. Also the fiberglass used as a sound deadening material causes dead air pockets, which is what quiets things down. The wrap used for downpipes retains the heat in the downpipe not letting it escape. The two forms off the fiberglass have different intended usages. If you are able to find a "fluffy" fiberglass that can withstand the heat, that should dampen the whine to almost nothing.

I think alot of the noise you hear comes from the compressor side of the turbo, I could be wrong though. I noticed a large jump in noise when I went to my hard intake piping.

I am planning to use wrap on my exhaust parts, primarily to quiet them down (single turbo setup, though -- not the stock twins). I also plan to ceramic coat them, both to add some mass that should help with the muffling, and to prevent corrosion (since header wrap is said to increase the rate of corrosion).

However, I don't know how much difference it will make. I do expect the difference to be noticable, and I figure every little bit helps. And at worst, all I will get is some thermal improvements for my efforts.

-Max

My downpipe is stainless steel (a cheapo ebay one) , and it is both coated (Jet-Hot) and wrapped (Thermotec). I didn't do any before / after tests, but it's quite tolerable IMHO. You can hear the turbos at initial spool-up, but they're not loud or intrusive at cruising speeds.

Check to make sure you don't have any exhaust leaks, they make a lot more noise when you've got a gasket that's not sealing correctly.

-s-

I believe that you can, or at least used to be able to get your hands on a cast downpipe without the cat. Someone else may know who makes this??? Did you also alter or change your intake in any way? make sure that both of the ~ 1" diameter hoses vent into your airbox. one is the blow off valve and the other is called something else, but until you really get into the boost this one vents and makes quite a bit of noise. You could also put some sound insulation on the firewall (make sure it can take engine bay temps), and you could better insulate the hood to help cut down on some of the noise transmitted into the cabin.

yes it does. i wrapped my downipipe and i noticed it was quieter in the cabin, but just as nice out the tailpipe :)

Some of that sound-deadening stuff in the doors would surely help noise levels when cruising, and perhaps some under the carpet above the exhaust would help deaden the exhaust noise, too. The spare tire well is also said to be a noisy spot that might benefit from some deadening material. Do you have a cargo divider and package-tray (hatch area cover thing)? I think those items help to reduce noise as well.

-Max

I got sound proof material from a local audio dealer and stuffed it everywhere I could. Doors, tire well, in the divider, underneath my carpet (seat area). Made a noticeable difference when cruising...

Hmm I just had my pre-cat removed and replaced with the stock downpipe from a series VIII RX-7 that had been imported into Aus. They had to do all sorts of work on the exhaust to get it past emissions and the downpipe ended up spare. Second hand but in pretty good nick, hadn't seen many kilometers. I'm actually unsure of the material but I'm guessing it's what your suggesting. I don't know where you can get them from because mine just sort of was laying around at the rotary place I take my car to. If you can't import the series VIII into the US (which for some reason I don't think you can but I don't really know anything about it, just seem to remember reading it somewhere so don't quote me) and that would make it hard to find parts, you might have to try looking to Japan.

Probably not worth the effort one would think..........

My dp is cast iron(stock mazda jdm dp),and when i wrapped it,the whine from the spooling went away...later i un-wrapped it......

Update: the answer is YES.

I took out my downpipe and wrapped it a couple days ago. With the windows rolled up, the turbo whine is MUCH quieter. It's a big help.

Thanks!

Take care,
Shad

i actually wrapped mine while it was on the car :)

Same here. It wasn't ALOT quieter after wrapping, but definitely noticable. I overlapped it quite a bit though.
But the biggest help for me was adding insulation and undercoating to the doors and spare tire well. That also made the doors sound much more solid when I close them.