Making a muffler

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ptuomov
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Re: Making a muffler

Post by ptuomov » Sun Oct 15, 2017 10:23 am

Borla mufflers hanging:
DAE42043-837B-4D17-903A-D677CBA497A7.jpeg
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[b]Paradigms often shift without the clutch[/b] -- [url]https://www.youtube.com/watch?v=cxn-LxwsrnU[/url]

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Re: Making a muffler

Post by ptuomov » Sun Oct 15, 2017 1:25 pm

Infinity pipe with two Borla mufflers:
B45F2FEA-8EE2-47E3-A8F0-48B5EFE2DF4C.jpeg
John is welding on the brackets which will work with the rubber isolators.
66FB464A-19BA-47FA-AD33-4EB1BDF1B712.jpeg
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[b]Paradigms often shift without the clutch[/b] -- [url]https://www.youtube.com/watch?v=cxn-LxwsrnU[/url]

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Re: Making a muffler

Post by ptuomov » Tue Oct 17, 2017 5:35 am

One more photo of the middle section before the fabrication of the rear section and the custom muffler starts:
4C72B578-6A16-4DDA-9A55-7F52A1C9D8A1.jpeg
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[b]Paradigms often shift without the clutch[/b] -- [url]https://www.youtube.com/watch?v=cxn-LxwsrnU[/url]

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Re: Making a muffler

Post by ptuomov » Thu Oct 19, 2017 10:19 pm

We are going to at least testing and probably using these cheap Vibrant bullet mufflers as the “test pipes” in place of the cats. They have 3.5 inlet and outlet, 9” overall length, and 4.125” outside diameter. They are about the same size as the cats, in other words, but without the restriction of the honeycomb. The purpose of them would be to quiet down the supersonic “blast waves” that we hypothesize are produced by the relatively early EVO of these cams. Made by vibrant performance from 304 stainless alloy and they are quite cheap on amazon.com. $110 shipped for the pair, so we’re going to at least look at them.
1340A264-089E-4AFF-A7DC-B2DF326905BD.jpeg
D9419EBC-A578-4014-B6AC-E2E625823E74.jpeg
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[b]Paradigms often shift without the clutch[/b] -- [url]https://www.youtube.com/watch?v=cxn-LxwsrnU[/url]

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Re: Making a muffler

Post by ptuomov » Sat Oct 28, 2017 10:54 am

First attempt at the rear muffler:
EE48D048-FF77-4AF5-9507-6532DEDC25F0.jpeg
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[b]Paradigms often shift without the clutch[/b] -- [url]https://www.youtube.com/watch?v=cxn-LxwsrnU[/url]

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Re: Making a muffler

Post by ptuomov » Sun Oct 29, 2017 2:32 pm

Here’s what the innards will look for this version. The perforated cone is a little big, could be smaller at the dual pipe end. The stainless wool mat will be wrapped around the perforated cone and then the packing material will fill the rest of the can.
2528F635-30DB-408D-BAD3-665BB79E8FB2.jpeg
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[b]Paradigms often shift without the clutch[/b] -- [url]https://www.youtube.com/watch?v=cxn-LxwsrnU[/url]

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Re: Making a muffler

Post by englertracing » Sun Oct 29, 2017 6:10 pm

You could get two perforated tubes and join them merge collector style....

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Re: Making a muffler

Post by ptuomov » Sun Oct 29, 2017 6:59 pm

englertracing wrote:
Sun Oct 29, 2017 6:10 pm
You could get two perforated tubes and join them merge collector style....
That’s one thing being considered, it’s s good idea to consider. Another is just squeezing two 3.5” perforated pipes into a d-shape at one end and merging them into a third, 4” pipe to the same effect. For mufflers that see fast flow velocities close to the turbine exit, those designs probably make sense.

The current prototype is much easier to fabricate and we’re going with that at least initially. One factor to consider is that this muffler is right at the tail pipe. By our computation the gas velocity is low enough and density high enough that this setup isn’t going to be much of a restriction. The available real estate makes the binding space constraint to be further upstream, and at the rear we can continue to use large pipes and enjoy the lower gas velocities. This single perforated cone may also silence better than a y-pipe perforated merge collector, we’ve read some tests that say one end with abrupt termination and one end conical shape silences effectively. In any case, when this muffler is up and running, we can measure the back pressure and listen to the sound and see if we got it right.
[b]Paradigms often shift without the clutch[/b] -- [url]https://www.youtube.com/watch?v=cxn-LxwsrnU[/url]

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Re: Making a muffler

Post by ptuomov » Sun Oct 29, 2017 7:33 pm

This is what I understand englertracing’s suggestion was. These photos are not from us, I copied them from someone working on an RX-7. Of course, we’d change the diameter from dual 3.5” to single 4.5” in our merge:

F11E30F6-3784-4F25-9F29-0ECA501589C4.jpeg
7DF06040-305D-4860-BAB3-3FEB2E3AA7A1.jpeg
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[b]Paradigms often shift without the clutch[/b] -- [url]https://www.youtube.com/watch?v=cxn-LxwsrnU[/url]

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Re: Making a muffler

Post by englertracing » Sun Oct 29, 2017 9:25 pm

Hmm, I had my mind on packing volume when I made that suggestion, and I've been making loads of merge collectors lately.... but, you do have more surface area with what you already have.....
Can you take a video of with and without this muffler, I am curious how it sounds

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Re: Making a muffler

Post by ptuomov » Sun Oct 29, 2017 9:36 pm

We’ll try, but there are going to be so many changes between this and the previous iteration that I don’t think we’ll have a clean comparison. We could try to run it without the whole back section for a sound check, but we’d have to hear shield it a bit as it’s a little too “blue flame” to show to the fuel system components there... it was so loud before, though, that we can tell for sure if the new mufflers and cross overs are working.
[b]Paradigms often shift without the clutch[/b] -- [url]https://www.youtube.com/watch?v=cxn-LxwsrnU[/url]

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Re: Making a muffler

Post by j-c-c » Mon Oct 30, 2017 11:28 am

So the above chambers have only a single cavity/resonant chamber? No intention of having at least one internal divider giving two different internal volumes?

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Re: Making a muffler

Post by ptuomov » Mon Oct 30, 2017 1:13 pm

j-c-c wrote:
Mon Oct 30, 2017 11:28 am
So the above chambers have only a single cavity/resonant chamber? No intention of having at least one internal divider giving two different internal volumes?
Nope. What would they accomplish in a muffler can of these dimension?
[b]Paradigms often shift without the clutch[/b] -- [url]https://www.youtube.com/watch?v=cxn-LxwsrnU[/url]

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Re: Making a muffler

Post by j-c-c » Mon Oct 30, 2017 1:25 pm

We are going in circles, one Helmholtz resonator vs two, tuned differently have a wider frequency attenuation range, albeit at higher hz, if restricted to same overall volume. My concern is drone results.

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Re: Making a muffler

Post by ptuomov » Mon Oct 30, 2017 1:38 pm

j-c-c wrote:
Mon Oct 30, 2017 1:25 pm
We are going in circles, one Helmholtz resonator vs two, tuned differently have a wider frequency attenuation range, albeit at higher hz, if restricted to same overall volume. My concern is drone results.
We'll see if it'll drone.

Talk about going in circles. I did a lot of research into muffler design and after the round trip came all the way back to the conclusion that the Borla (/Magnaflow) type packed muffler design is the optimum for a street driven performance car which needs broadband noise suppression and has limited space for mufflers. This is especially the case for the tailpipe muffler at the end of the exhaust system.

If this system now being built has an audibly bothering drone to it at some specific frequency, then the next step is to redo the center mufflers (currently, off-the-shelf Borlas) with custom two chamber straight-thru design where the front chamber is a Helmholtz resonator tuned to suppress the drone frequency and/or to put a valve into the passenger side rear leg pipe to create a tuned side-branch resonator tuned to suppress the drone frequency.
[b]Paradigms often shift without the clutch[/b] -- [url]https://www.youtube.com/watch?v=cxn-LxwsrnU[/url]

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