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Making a muffler

General engine tech -- Drag Racing to Circle Track

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ptuomov
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Re: Making a muffler

Post by ptuomov » Thu May 23, 2019 1:11 pm

David Redszus wrote:
Thu May 23, 2019 12:16 pm
ptuomov wrote:
Wed May 22, 2019 8:09 pm
The resonators take in 3.5” pipes. The pipe size goes up to 3.5” at the point where the wastegate sump pipe merges to the flow. There are photos earlier in this thread.
Reviewing a silencer design program, I find that a straight thru, perforated tube, design will attenuate noise at specific frequencies, without flow loss. The issues to address are: packaging, attenuation targets by dB and frequency. Other design factors are gas temperature and wall thickness.

How much noise reduction do you need?
The exhaust project described in this thread is done and it was a success. The noise level is finally acceptable. Once the transmission is back on, we’ll get tail pipe noise measurements on the dyno.

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Re: Making a muffler

Post by GARY C » Mon May 27, 2019 7:00 am

I ran across this, "Build A Titanium Muffler LIVE!" https://www.youtube.com/watch?v=qLZA97fPXOM

Using parts from, https://www.ticonindustries.com/
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Re: Making a muffler

Post by dfarr67 » Thu May 30, 2019 10:22 am

Any experience with:

1/ Flowmaster Hushpower- seems similar concept to this thread.

2/ current quietest biggest muffler in 4in pipe dia.

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Re: Making a muffler

Post by ptuomov » Thu May 30, 2019 10:43 am

dfarr67 wrote:
Thu May 30, 2019 10:22 am
Any experience with:

1/ Flowmaster Hushpower- seems similar concept to this thread.

2/ current quietest biggest muffler in 4in pipe dia.
1) I don't have practical experience with the Huspower mufflers. However, after studying the topic my opinion is that a simple Borla or Magnaflow muffler of the same case volume is going to give you a better tradeoff between back pressure and sound suppression. This is just from theory, and reading a student group writeup experimenting with that muffler.

2) I don't know, but I would guess that certain Donaldson mufflers would be among the quietest, and largest. Something like the M101158 but in 4" in/out.

The above is speculation, others who know might want to chime in.

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Re: Making a muffler

Post by ptuomov » Wed Jul 24, 2019 7:36 am

Here’s a dyno pull up to about 6300 rpm with the new exhaust and fabricated muffler. You have to click the sound on. I think it sounds nice, and doesn’t pop with a little bit of flame:


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Re: Making a muffler

Post by Kevin Johnson » Wed Jul 24, 2019 8:24 am

https://malegislature.gov/laws/generall ... /section16

Oh man, no Lake pipes allowed.

Bummer.

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Re: Making a muffler

Post by ptuomov » Wed Jul 24, 2019 12:48 pm

Kevin Johnson wrote:
Wed Jul 24, 2019 8:24 am
https://malegislature.gov/laws/generall ... /section16

Oh man, no Lake pipes allowed.Bummer.
“Whoever violates the provisions of this paragraph shall be punished by a fine of not more than fifty dollars.”

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Re: Making a muffler

Post by dfarr67 » Wed Sep 04, 2019 10:57 am

Curious, was told by a shop that a class of muffler will sound similar regardless of manufacturer ie straight through perforated muffler like Magnaflow, Borla, ProFlo, etc. I have a 4in ProFlow stainless diesel cat back on a truck- muffler is 4in in/out x 24in x 7in dia and am looking for a quieter replacement, Magnaflow has a 24in ish replacement, Hooke MaxFlow, Donaldson chambered diesel in 44 in long 9 in case dia and a few others. I pretty much knew the muffler would be inadequate but I was after the SS and mandrel bends.

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Re: Making a muffler

Post by xr4x4ti » Wed Sep 04, 2019 9:47 pm

dfarr67 wrote:
Wed Sep 04, 2019 10:57 am
Curious, was told by a shop that a class of muffler will sound similar regardless of manufacturer ie straight through perforated muffler like Magnaflow, Borla, ProFlo, etc. I have a 4in ProFlow stainless diesel cat back on a truck- muffler is 4in in/out x 24in x 7in dia and am looking for a quieter replacement, Magnaflow has a 24in ish replacement, Hooke MaxFlow, Donaldson chambered diesel in 44 in long 9 in case dia and a few others. I pretty much knew the muffler would be inadequate but I was after the SS and mandrel bends.
The basic statement is true, but it doesn't mean it will be quiet.

The basic problem with a 4in straight through muffler is that a lot of the exhaust gas can go right down the middle and not get exposed to the sound absorbing material. You want the most amount of surface area for a give cross sectional area. Beyond that you want the most of amount of sound absorbing material. In your case I would "Y" it out and put dual 3in mufflers on and then "y" it back together if you still want a single exit.

I just went through this on my car. Even though I knew better I put a single 4in muffler on my turbo SBF after upgrading from a single 3in exhaust to a 4in inch. Battled it for a couple of years trying different 4in combos, nothing worked. Finally this year I split it into a pair of 3in mufflers (I had to make one, hence why I hadn't done it in the past) and now all is good. I simple physics, don't fight it:)

Here is my patent on a pneumatic muffler that is currently in production. Notice how it splits into two ports and the ports are not round. All done to increase the surface area relative to the cross sectional area. https://patents.google.com/patent/US20130058802/pt-pt

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Re: Making a muffler

Post by Leftcoaster » Thu Sep 05, 2019 1:23 am

Almost 20 yrs ago a twin rotor Mazda powered gyrocopter was being developed in a neighbouring hanger - - combining low back pressure with acceptable noise levels proved elusive until the PhD Mech involved incorporated the principles of a Russian? research paper, in this case calling for the gases to exit via rectangular cross section piping once they'd passed through the "muffler"

His design wound the rectangular section piping around the outside of a cylindrical expansion chamber of conventional volume which tapered towards the intake and outlet, understandably the whole apparatus being compact and of low mass

To my ear it certainly sounded quieter, and I understand it passed relevant noise regulations - - my recollection is the rectangular cross section outlet pipe of approximately 2" x 2" x 4' was considered responsible for superior sound suppression, without increasing the back pressure of round cross section pipe of similar area and length

Unfortunately I've no photos to share, and wonder if anyone else has seen or read of this technology?

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Re: Making a muffler

Post by Circlotron » Thu Sep 05, 2019 1:43 am

xr4x4ti wrote:
Wed Sep 04, 2019 9:47 pm
The basic problem with a 4in straight through muffler is that a lot of the exhaust gas can go right down the middle and not get exposed to the sound absorbing material. You want the most amount of surface area for a give cross sectional area.
Is there a straight through muffler where the perforated tube down the centre is more of an oval shape, much like the shape of the outer casing? Same cross sectional area as a round tube, but squashed and widened. That would give more area exposed to sound absorbing material, but at the expense of reducing the available volume of that material somewhat.

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Re: Making a muffler

Post by Kevin Johnson » Thu Sep 05, 2019 1:57 am

There has been much research in wave propagation in circular versus rectangular cross-section duct work.

https://books.google.com/books?hl=en&lr ... 22&f=false

Use the above embedded search parameters in Google Scholar to bring up many citations/patents. ["rectangular" cross section exhaust pipe "sound attenuation"]

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Re: Making a muffler

Post by emsvitil » Thu Sep 05, 2019 2:13 am

I remember reading (a long time ago) in a book about exhaust systems where the straight section of the muffler core was a continous spiral path.


Something like this, but constant.

Image

https://www.summitracing.com/parts/pte- ... lhEALw_wcB



Maybe vary the twist so there's less backpressure.

Use something like this:

Image
Ed

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Re: Making a muffler

Post by ptuomov » Thu Sep 05, 2019 7:49 am

xr4x4ti wrote:
Wed Sep 04, 2019 9:47 pm
dfarr67 wrote:
Wed Sep 04, 2019 10:57 am
Curious, was told by a shop that a class of muffler will sound similar regardless of manufacturer ie straight through perforated muffler like Magnaflow, Borla, ProFlo, etc. I have a 4in ProFlow stainless diesel cat back on a truck- muffler is 4in in/out x 24in x 7in dia and am looking for a quieter replacement, Magnaflow has a 24in ish replacement, Hooke MaxFlow, Donaldson chambered diesel in 44 in long 9 in case dia and a few others. I pretty much knew the muffler would be inadequate but I was after the SS and mandrel bends.
The basic statement is true, but it doesn't mean it will be quiet.

The basic problem with a 4in straight through muffler is that a lot of the exhaust gas can go right down the middle and not get exposed to the sound absorbing material. You want the most amount of surface area for a give cross sectional area. Beyond that you want the most of amount of sound absorbing material. In your case I would "Y" it out and put dual 3in mufflers on and then "y" it back together if you still want a single exit.

I just went through this on my car. Even though I knew better I put a single 4in muffler on my turbo SBF after upgrading from a single 3in exhaust to a 4in inch. Battled it for a couple of years trying different 4in combos, nothing worked. Finally this year I split it into a pair of 3in mufflers (I had to make one, hence why I hadn't done it in the past) and now all is good. I simple physics, don't fight it:)

Here is my patent on a pneumatic muffler that is currently in production. Notice how it splits into two ports and the ports are not round. All done to increase the surface area relative to the cross sectional area. https://patents.google.com/patent/US20130058802/pt-pt
Does Borla’s multi core muffler work with the same principle as splitting the path into multiple flow path lengths?

If you have the room, splitting the flow path to two smaller pipes and then making the path lengths significantly unequal in length offers a lot of sound cancellation benefits at high frequencies. In a turbo car, there are good opportunities for this with, for example, the wastegate circuit.

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Re: Making a muffler

Post by ptuomov » Thu Sep 05, 2019 7:52 am

emsvitil wrote:
Thu Sep 05, 2019 2:13 am
I remember reading (a long time ago) in a book about exhaust systems where the straight section of the muffler core was a continous spiral path.


Something like this, but constant.

Image

https://www.summitracing.com/parts/pte- ... lhEALw_wcB


Maybe vary the twist so there's less backpressure.

Use something like this:

Image
That auger muffler style has by my understanding turned out to be inefficient in terms of back pressure, volume, and sound suppression.

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