Making a muffler

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englertracing
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Re: Making a muffler

Post by englertracing » Wed May 24, 2017 4:09 pm


ptuomov
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Re: Making a muffler

Post by ptuomov » Wed May 24, 2017 4:14 pm

englertracing wrote:Spec 31 packing.....

https://www.bristolcore.com/product_p/14214.htm
I was looking at that. One plan would be to use their HD steel wool mat (http://www.bristolcore.com/product_p/14489.htm) around the perforated sleeve and also on the bottom of the muffler can where the drain hole is. Then fill the rest of the large can with their Spec 31 packing material. I'm thinking that HD steel wool mat would prevent blowout either thru the perforations or the drain hole. Then that Spec 31 would have a good chance of living happily ever after there.
[b]Paradigms often shift without the clutch[/b] -- [url]https://www.youtube.com/watch?v=cxn-LxwsrnU[/url]

ijames
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Re: Making a muffler

Post by ijames » Wed May 24, 2017 4:24 pm

Would it be beneficial to put your soft packing in as layers between either SS wool mat or SS mesh? That way each layer might get packed down but you won't wind up with large empty cavities nearly as fast. If you are going to have say 3" of soft material, maybe break that into 6 layers of 1/2" each, or thinner, or whatever looks good to you :lol: . For this I'm thinking of SS screen material, so only one or two wires thick, just for support with minimum volume but not absorption.

englertracing
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Re: Making a muffler

Post by englertracing » Wed May 24, 2017 6:19 pm

The spec 31 is good I have it in about a dozen motorcycle cans.

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Re: Making a muffler

Post by ptuomov » Wed May 24, 2017 7:34 pm

englertracing wrote:The spec 31 is good I have it in about a dozen motorcycle cans.
Thanks, good to know. How long does it last in a motorcycle muffler? With or without the stainless steel mesh layer as an insulation on the perforated pipe?
[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 pcnsd » Wed May 24, 2017 9:17 pm

ptuomov wrote:
englertracing wrote:Spec 31 packing.....

https://www.bristolcore.com/product_p/14214.htm
I was looking at that. One plan would be to use their HD steel wool mat (http://www.bristolcore.com/product_p/14489.htm) around the perforated sleeve and also on the bottom of the muffler can where the drain hole is. Then fill the rest of the large can with their Spec 31 packing material. I'm thinking that HD steel wool mat would prevent blowout either thru the perforations or the drain hole. Then that Spec 31 would have a good chance of living happily ever after there.
The above is the long strand fiberglass I was referring to. I buy it though our local race club. They keep it on hand for those who fail sound testing.

I think your basic concept of using a SS inner wrap followed by the Spec 31 packing with a buffer of SS near a drain hole is sound.

You likely have been there, but here is a link to a company that makes a SS mat product they claim is superior to SS wool for use as an inner layer wrap.
http://steelwooldirect.com/muffler-packing/

And a muffler packing FAQ which you probably also have read.
http://www.supertrapp.com/images/pdfs/M ... ng-FAQ.pdf

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Re: Making a muffler

Post by englertracing » Thu May 25, 2017 1:41 am

No wrap on the stuff we built.
Wrap on an oem Honda motorcycle repack.

So far it stays in rather well,
But these are singles, with lots of airflow over the exhaust, and lower (methanol) egt
And they are race stuff so not a terribly high amount of run time,
When we have taken some apart to make some changes the packing looked great.

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Re: Making a muffler

Post by ptuomov » Thu May 25, 2017 8:23 am

englertracing wrote:No wrap on the stuff we built.
Wrap on an oem Honda motorcycle repack.

So far it stays in rather well,
But these are singles, with lots of airflow over the exhaust, and lower (methanol) egt
And they are race stuff so not a terribly high amount of run time,
When we have taken some apart to make some changes the packing looked great.
Thanks for the first-hand info. From the heat perspective it should work well for me then, as there's that stainless steel mat around the perforated core, this is the rear muffler about 8-9 feet from the turbo in terms of the flow path, and the can bottom gets decent air flow. From the pressure pulse perspective it should be working ok, too, as there are 8 cylinders which have been combined by that point and a large amount of exhaust volume between the turbos and the rear muffler.
[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 May 30, 2017 5:50 pm

The materials that Bristol Core recommended:
IMG_0025.JPG
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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 Jun 03, 2017 9:55 pm

Ok, while the muffler and exhaust materials have been bough ($$$ to make it all from long-lasting materials), here are some additional thoughts about the sound on a twin turbo V8.

What I want is the car to be relatively quiet under 3000 rpm and part throttle. It can be loud at full throttle and above 3000 rpm. Furthermore, I want an exhaust note above 3000 rpm that communicates the rpm level well. Then, finally, what I want is the exhaust to flow really well.

Here's the design strategy that is slowly emerging from my hazy thoughts.

First, collect all the exhaust pulses to a common pipe with as close to equal flow paths as possible. The idea here is to get most of the sound pressure to the 4th engine order, that is, pulsing with the engine firing. For a V8 with four exhaust blowdown events per engine rotation, that means 40Hz at 600rpm, 200Hz at 3000rpm, 400Hz at 6000rpm, etc. The various half orders should cancel.

If I can keep the 4th EO frequency the dominant one, then what I want is very good muffling below 200Hz (corresponding to 3000rpm of 4th EO) and above 440Hz (corresponding to 6600rpm which is about the redline). In the 200-440Hz range, some of the sound can come thru because it'll roar with the rpms, which is fine.

The turbocharger will muffler frequencies above 500Hz or so and very effectively take out frequencies over 1000Hz. Add the packed absorption muffler to the end (the home-made one that is the subject of this thread), and I am thinking the top end of the frequency range is taken care of.

What is left to take care of is the frequency range under 200Hz. If the idle is set to 750rpm, that means 50-200Hz range is the focus. The two Borla XR-1 Sportsman rear axle mufflers that I have in the system that's being implemented aren't really geared towards those frequencies.

If what's being built now doesn't work well, then I think the next step is to see if something could be done to those Borla XR-1's (or the space they are occupying) to focus more on the 50-200Hz range.
[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 » Wed Jun 07, 2017 11:27 am

The more I read about this, the greater my respect for the factory exhaust engineers. I do what I can, they do whatever they want. The unsolved problems in exhaust sound seem to be mostly related to the marketing department more accurately extracting the information from consumers what they think when they hear a particular exhaust note. The engineers can deliver whatever they are asked.

For example, here's a Ford truck resonator that simply takes out the unwanted low frequencies that I also want to get rid of:
2009muffler.jpg
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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 In-Tech » Wed Jun 07, 2017 12:09 pm

I rented a 2016 ecoboost explorer and the exhaust sound was phenomenal, smooth and quiet at light throttle and big block throaty at full throttle. I always meant to get a good look at it in the air but never did. You might have a gander around the interweb and see if you can find some pics. I am definitely not a ford guy but I was quite impressed with the whole package.
Heat is energy, energy is horsepower...but you gotta control the heat.
-Carl

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Re: Making a muffler

Post by j-c-c » Wed Jun 07, 2017 1:19 pm

" Add the packed absorption muffler to the end (the home-made one that is the subject of this thread), and I am thinking the top end of the frequency range is taken care of.

What is left to take care of is the frequency range under 200Hz. If the idle is set to 750rpm, that means 50-200Hz range is the focus. The two Borla XR-1 Sportsman rear axle mufflers that I have in the system that's being implemented aren't really geared towards those frequencies. "

This thinking implies 'packing" has positive impact at 200Hz and below, and unless we are talking thickness greater then 12"?, and/or unless packed dense enough to be a mass barrier, I think not .

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Re: Making a muffler

Post by ptuomov » Wed Jun 07, 2017 1:37 pm

j-c-c wrote:" Add the packed absorption muffler to the end (the home-made one that is the subject of this thread), and I am thinking the top end of the frequency range is taken care of.

What is left to take care of is the frequency range under 200Hz. If the idle is set to 750rpm, that means 50-200Hz range is the focus. The two Borla XR-1 Sportsman rear axle mufflers that I have in the system that's being implemented aren't really geared towards those frequencies. "

This thinking implies 'packing" has positive impact at 200Hz and below, and unless we are talking thickness greater then 12"?, and/or unless packed dense enough to be a mass barrier, I think not .
I don't think you can interpret what I wrote in that way. I certainly didn't mean that. Then again, English as a second language, so all your base are belong to us.

To be clear, the off-the-shelf Borla XR-1 mufflers may not be ideal for my purposes as the center mufflers because they are likely to be more effective at high frequencies (over 200Hz) and less effective at low frequencies (under 200Hz) than desired. Hence, my crystal ball says that those store-bought mufflers may also be replaced with fabricated muffler/resonators in the future.
[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 pdq67 » Wed Jun 07, 2017 3:31 pm

ptuomov wrote:
pdq67 wrote:OK, I'm back!

I have a 2.5" x 18" long and a 2.5" x 12" long way old school JCW turbo mufflers on my car down each side now that exit like stock. ('67SS/RS Camaro car here)... The long one under my front seat and the short one where the stock resonator fits.. This was behind my, "Strong Arm", 406 and I kept it for my 496!!

I want to change to the WDT, smooth perforated inner pipe glass packs by say installing a long and a short pair of them split going in and then gathered together going out down both sides, then to transverse glass packs right behind my rear end?? Exiting like stock. pdq67
Do you have photos? How much power does the car make?

I am not sure whether you're seeking opinions or what, but if you are, I'm interested in hearing what your objective is with these changes?
Now just cheap BBC 4-tube, long tube headers at 2.5" dia., 550 hp/580 t BBC here.. Four cheap turbos and 550 hp/580 t BBC here..

But later I want two "Y"d glass packs down each side and two in the stock transverse location one on top of the other just behind the rear end before the gas tank and exit like stock.

pdq67

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