Well, let’s see. Today’s Thursday, not bad, but not as good as Tuesday because that way there’s at least 5 days until Monday happens again… What’s for supper tomorrow? Ah, let’s check the fridge. Hum, beer. More beer. Wine. Oh, that vintage stuff - it’s got the screw-off cap. More beer. What can we have with beer? I know! “It’s not delivery, it’s FRENCH!” Yeah, that’ll work. And while it’s baking I can piece together that sonic atomizer for the fuel injection system. Hum, I’ll need 2 rubber bands, 5 large paperclips, common household white glue, exactly 6 1/64” of 1/8” vacuum hose, a hand full of pipe cleaners, half of an empty beer can…

Oh! Sorry. I didn’t realize this thing was turned on.

P5Freak –

Thanks for the photos! Size wise, that looks a lot like the muffler inserts I’ve seen. Probably the only difference I can tell is most of those have a length of pipe stuck through the hole. Looks like a good fit, too.

Silver_p5_owner –

I know what you mean about the exhaust – I really like the look and the growl, and the burble at idle is great, but the drone just wears me out.

marc38 –

I might need to add experiment #3 to the list - that’s interesting about the heat shield. I know on the topside Mazda installed the factory equivalent of Dynamat directly above the shield. I haven’t looked to see how the shield's mounted – it might be something I can take off for a test. A possible “resonance coupler.” It ‘d be funny if that were the end cause of our drone…

 

Okay...

If you want the part that I have.

Order part "STPRR100FR" at www.cbtimports.com

It's $28 + shipping. You will have to call or email to order it as the website probably doesn't show this part.

It will restrict you down to the original size of the stock muffler (maybe a bit more).

The image below shows what the part looks like. Earlier I told you that I need to get it out so that I can cut off the pipe thats on the inlet side (you'll notice it, its the slanted portion of the silencer, its got to go).

http://www.cbtimports.com/stntnrestrictor.jpg

 

Nice!

P5Freak - do you think there would be any advantage if you straightened and reattached the pipe? Also, is it possible to attach the plug with a screw insert - I noticed that was how they did it originally.

And Many Thanks for tracking down a resource! The cost isn't bad at all!

 

BigBadWulf,


Straightened/Reattachment? You probably could heat it up and bend it. That would work/If I can get it out I'll try and do just that.

Plug/screw insert? I think that it can be used. If you look at my pictures, it's facing upside down, another reason to get it out.
The other thing you can do is just screw a screw into the tailpipe just after the insert to keep it from falling out (although falling out is not a concern right now, at this point I wish it would fall out cause I can't get it out).

My only caution with this insert is if you only do city/short drives that do not allow your exhaust to heatup, you will probably run into issues with your intermediate pipe rusting due to water buildup. My car never sees short drives (I live in da Maine woods) so evaporation is inevitable.

But with most silencers/reducers this problem exists anyway.

The only difference between this silencer and all the others is that you can't see it at all and the exhaust still has a great bark to it outside of the car. Ahh life is good!

 

P5Freak,

Anyway you can post up some sound files of how it sounds both in and out of your car.

thanks.

RC

 

Imagestation and most other picture posting sites dont allow sound clips. Can I email them to you? If so, lmk your email. Private message me, then if you know of a place to upload them to, you could post it for the rest of the group.

 

p5freak,

sent you a PM..

thanks

 

btw – Like a Wulf with a bone, I still plan a series of experiments this weekend, provided the weather cooperates. Pizza’s in the freezer already. Got the reducers. (2 ¼” O.D. down to 1 3/8” I.D.) Found a handy piece of 2” pipe about 5 ½” long. And I’ll check the heat shield as long as I’m under there.

 

Well I ran a heat sheild test and I would like someone else to try something similar to prove or disprove what I thought I experienced. I had about a square foot of 1/4" neoprene rubber sheet laying around so I cut it into strips and rolled it up and pushed and squeezed it into any open area between the heat shield and the chassis panels to try to curtail any vibration that would develop. My first impression was that it helped. I could actually hear my valve train and injectors clicking under WOT. The exhaust note was still very apparent yet not so boomy. As far as I can tell the heat shield is held to the body with four rivets and I'm not quite ready to cut or drill the heads off just yet to remove it and find it's not a major contributor to the problem. Not being a sonic specialist, but only a normal guy with a good deal of common sense, I could see this thin metal panel acting as an amplifier/transducer (kind of like electrostatic speakers) and transmitting a resonance thru the chassis via the four mechanically connected rivets. Anyone with other opinions about this? Thanks to whoever it was who brought the heat sheild into play as a possible factor.

Jeff M

 

Thats a good news.
Thanks siver_p5, I have do something similar and get good result to. And that whit the stock muffler...Next time i will put fiberglass wool.
Better to keep the heat sheild.

 

Ladies and gentlemen, we may have what I think is a Second Solution.

Following a lusciously delectable feast, I swapped out my exhaust yet one more time.

While I was under there, I checked the heat shield, plucked it a few times, (Yes, a nice resonance…) took a look at the big-*** rivets holding it on, took a second look, then said forget it - that sucker’s on to stay. So much for experiment #3. (silver_p5_owner - you tried what I had in mind to do later. I agree this thing is probably a source of some of our noise.)





Next up, I tried two attractively finished reducers, the first going from 2 ¼” down to 2”, the second going from 2” down to 1 ½”. Stuck them together and then put the assembly with the narrow end in the muffler. Don’t even waste your money. ($3.16, total.) I think the damn thing was even louder then before, if such a thing is possible. Thus ended experiment #2. (From my past experience, these make good artillery shells for a “road canon,” so it’s not a complete loss.)





Finally, I scrounged a piece of pipe. (It even looks like a scrounged piece of pipe.) I don’t know what it’s made of – most likely black iron used in plumbing – but my interest were in the measurements: 2” I.D. and roughly 5 ½” long. I tamped it in, (Best done when the exhaust is hot – it’ll set better, but be careful with your fingers.) and then started my trial run. (Residential streets, followed by about 5 miles of 35-60 MPH driving, finished with a 5-mile jog on the Interstate running from 65 to 80 MPH.)





Hum, a little raspier up to 3,000 RPM, but the sound seems to level off above that with more tone than drone. Somewhere in that 60 to 70% range of loudness compared to the exhaust without the pipe. Livable.

P5Freak – you might try a piece of pipe and compare the sound to your plug insert. I’d be interested if this is anywhere close to what you’ve achieved. The one advantage I see to the pipe is that it’s less restrictive to flow. If the plug is quieter, I consider $28 a cheap fix for the noise.

marc38 – Thanks for your input about the pipe and heat shield!

Test results compliments of BBW Test Labs, a subsidiary of Wulfswagon.

 

FWIW, I've never been keen on putting a restrictor in the pipe. I want the flow, a restrictor may quiet the sound but I can't believe that you won't lose the 2 or 3 WHP that the free flow gives. Why not go back to the factory exhaust? I want the sound, the look and the minimal HP gain. Also I don't want to introduce a rust inducive chunk of metal in my $200 exhaust. I'm following the goal of less transmission into the body structure. The heat shield's rivet heads are accessable in the trunk area and tomorrow they and the shield will be gone. I'll let you all know how it goes and any future add-ons i try to quell the BOOM!

Jeff M.

 

To anyone who tries the pipe approach: I used black iron pipe for experimentation, only. If this works for you, I’d suggest using a piece of 304 stainless pipe (You can probably find something like this at a local muffler shop.) for a permanent installation. Also, you’ll need to drill a hole in the side or bottom and insert a stainless screw so you don’t lose your “precious.”

Ta ta,
W.

 

Silver_p5

Hey guys dont mess whit the heatsheild above the silencer.
I had all made thest with it and it's not an issue.

What i talk about is the heat sheild over the resonator its hold by four scews not rivet and it is under de driver seat.

Great work BBwoulf !!!!

 

Alright, I'm confused, you say it's the diameter of the mazdaspeed pipe that creates the resonance. Also that the heat sheild that concerns you is the center one. The Mspeed pipe connects near the rear end of the car. Do the vibrations travel forwards thru the exhaust system and then bounce into the interior? My unwanted noise seems to be directional to the rear of the car, not near the center. As I said before, I am no sonic specialist and I would like to better understand how and why this is happening. I believe it was you who also mentioned a pressure/resistance drop caused by the ID of the Mspeed and the ID of the center pipe that is a factor in this. Could something be done in the junction area where the Mspeed bolts to the factory center pipe, in a fashion to taper the transition between the 2 pipes? Would matching ID pipes forward of the Mspeed help? There have been some complaints about the Bosal Cat-Back (mfg of our axle back) similar to ours. Any info would be greatly appreciated. I really don't like the idea of sticking a restrictive pipe in my big fat pipe, if you know what I mean.

TIA
Jeff M