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SS wool is not a good choice. If tends to mat down/compress under the heat and pulsing, in addition to not offering any real absorption capacity due to being metal. I’ve run both it and stainless scrubber/shavings material, was never satisfied with the results, adds weight too. I have a big box off stainless wool somewhere, like a lifetime supply. Bought a “super secret” packing with one muffler specifically for rotary racing and it was was just stainless wire mesh rolled up. Very heavy and very ineffective, supposedly what Speedsource and others were running on their 3-rotor RX8s.
Ceramic fiber that can take the heat is way better. I was buying a ceramic fiber muffler packing product from Germany that was awesome, but the distributor I was buying it from stopped selling it and it’s now hard to find. I didn’t really need any more as it lasts and works very well. It’s more like loose strings of ceramic fiber material and you just pack it in, but not too tightly.
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Am considering doing a custom version of this (with or without the extra male bit) plus a dummy tip on RHS. Probably in mild steel painted in high temp black. Thoughts and ideas?
My OEM muffler has got to be dead internally at 15 yrs.
as was previously stated, there’s not really anything inside of it to go dead
you can gimmick it out all you want with extra piping, elbows, i.e. additional cost, etc. , but ultimately a spiral baffle type in the middle and two small canisters with the proper packing in the rear (similar to the RX8 Mazdaspeed rear exhaust) will get it done. Or a larger single muffler. I can’t say I’ve ever seen one of the frequency contraptions ever effectively applied to a rotary exhaust and am not really much of a believer in them. I tend to look at most of those things as snake oil to entice people who lack technical discernment. Tone and drone are highly subjective though and I haven’t driven an RX8 much on the street since forever. My only real concern now is weight and keeping it under a certain sound limit under WOT.
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Thanks Team. I consider myself schooled and therefore informed. I will look into the ceramic matting. Would you consider the ceramic mat inside twin 4 inch resonators suitable for street use and back roads? Mostly the latter.
My current exhaust configuration is stock header, mazsport midpipe (apparently both resonators they used are racing beat which makes this midpipe rather quiet) and stock catback.
Is stock piping is 2.5"ID or OD?
I am thinking opening that pipe on the back of the stock muffler and welding 2.5" vband clamp (like below) and just connecting straight 2.5" ID pipe long enough to bring exhaust back out though the center opening (under cover plate) on the bumper. Will need to buy additional clamp ring and weld it shut for when I want to revert back to stock muffler only. Wonder what will it sound like with basically straight trough exhaust and dual resonated midpipe. According to Racing beat removing rear muffler gets you +5hp :-).
Last edited by Nadrealista; Feb 18, 2021 at 12:41 PM.
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Here is the OEM, my previous pic was Scorpion aka PZ.
No wonder it is very silent and civilized, they could make it smaller to have a bigger boot :/ OEM Exhaust muffler/chamber
they more or less use perforations without packing, directional changes, and chambers to attenuate the sound from a roar to a hiss without adversely affecting flow. The Spintech muffler design is similar in concept.
the OE tubing is metric and will require adaptation to a standard US size. I want to say it was 60mm going into the S1 muffler and I adapted it to 2.5”, but that was a long time ago and my memory isn’t what it used to be.
thank you for posting this! looks like all kinds of gymnastics for exhaust gas to get out :-)..squeeze trough two sets of holes then turn 180 degrees to find a way out.. on S2 stock piping is 2.5" OD into muffler, my mazsport midpipe is 3" all the way no neckdowns:
Team how loud do you think it would be with dual resonated midpipe and OEM muffler replaced with one 3" moroso auger muffler or do a y split and 2 moroso auger mufflers?
or open heart surgery of stock muffler :-)
Last edited by Nadrealista; Mar 2, 2021 at 12:25 PM.
Thanks Moto for your efforts. You have got me thinking about modifying a spare box that is just taking up storage space anyway. Considering slighly different 4 cuts to internals to above pic that Nad has shown above. I think this could bring back some bark while keeping some internal structure to keep drone at bay somewhat. Open to ideas.
Edited pic due to further ideas and discussion points. Purple dots added in 1/4 inch holes x12 per side. Green is ceramic matting but unsure of positioning. Please chime in about above if you know about them.
Wow, would not have thought the OEM muffler worked like that. I wonder how it compares to other popular aftermarket designs. Looking at the racing beat REV8 myself. I know it's a tad heavier than the OEM.
it’s quite good considering how loud it is without it. The main performance benefit of replacing it is the weight savings rather than flow improvement.
However the one I remember from way back, the guy cut it open from the top side, drilled out most of the perforations to a larger diameter, then welded it back up to get more sound and what he thought was more flow through it. IME it’s not really the restriction point in the OE exhaust system though.
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Modifying OEM Catback is the waste of time/money unless having a welding machine lying around.
You can pick a decent Catback with under name of toyosport/japseed for a reasonable price. They are great for shooting flames ;D
The only downside is the so-called drone noise which I personally like as it is like posing sound.
Also for drone noise, you can add a little cute Helmholtz resonator.
The only cost to me to mod my spare OEM will be about 25$ for a metre of ceramic mat that i intend to halve, roll up, and jam under outlet horns of outer box sections. Should not move or cause any blockage issues. Only real cost is a bit of time, I like to test stuff! 😉 Could be a winner or loser, we will see.
Im happy to cut, dremel, weld back up and test for noise and drone. I did do pretesting so i will know the difference. I'll report back at some stage and maybe even pull together a basic DIY if desirabe outcome. Wont bother if poo.
So I spent a bit bit of time and effort on this mod and I am very happy with the results overall.
This is a great sound and exhaust flow mod period.
I was never really chasing power, we all know how that goes anyway. I mainly wanted a decent bark from my fresh rebuild without spending $$ on inferior quality materials. Also retaining OEM look.
All you need to do this mod is an angle grinder with a couple of cut off disks, a dremel, and a mate with a TIG welder. I also used 3 cans of VHT flameproof paint in primer/ black/ clear coat for a decent finish which is entirely a personal choice.
I will let the pics do the talking other thank did do pre and post sound tests using app on mobile phone. Results as follows.
OEM back box stationary test 3 m behind car at 0.5 m off ground @ 3000 rpm = 80 db
In car @ 100km/hr 3000rpm in 6th gear on flat road = 75 db
Modified back box same tests as above.
90 db behind car and 80 db in car.
Drone did not change between tests (which I had no way of measuring btw. Just by ear.)
Pics added separately due to site time out issue maybe.
Hopefully the packing doesn't burn up too fast..... it likely won't last long though so expect the sound to change
+1 this.
Maybe 5-6 drive cycles? lol hopefully it doesnt mat./compact itself and block out your exhaust completely. Looks like a disaster waiting to happen. Just get a quality muffler and call it a day.
Completely agree that it will be interesting to see how long the ceramic matting lasts. This was one of the reasons for my sound testing in and out of car to retest later on.Thanks to Team for the ceramic mat suggestion as I was originally looking at the SS wool. I think it would have been a big fail. The ceramic Matt used was rated to 1260 degC. It should (touch wood) outlast temps of the flameproof paint rated at only 1100 degC. Time will tell. Will update if any of it fails.
I have had an OEM backbox on that was polished and had 3 coats of VHT flameproof clear paint for 1000km (without any primer, no issues at all) and this car works hard on weekends!
Last edited by XDragon8; May 14, 2021 at 03:01 AM.
Its threaded ceramic mat. The race MX guys and road bikers use it as its super light, has great sound deadening qualities and rated to 1260deg C from memory.
It can be found on ebay or in higher end bike shops.
Just make sure its threaded or stiched. You can get some loose fibres where you cut it but no problems so far.
From pics above i mainly placed matting in outer sections then welded back up so it cannot dislodge (hopefully) but time anduse will reveal any issues. None yet.
this is the stuff I used successfully in my racing mufflers; Silent Sport Premium
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no longer distributed in the USA, you have to order it from Germany, be advised that they sell a lower temp packing that is not called “premium”, so make sure it’s the “premium” one.
technically only rated for 750*C (~1400*F), but it worked good for me at the very rear muffler area
this is the USA company that used to sell it, they have some other packing now that looks similar, but I don’t have any temp info or experience with it
