Muffler Fabrication & Design

[evanfrucht]

Has anyone welded up their own muffler from scratch? What did you do and how did it work?

I'm working on one now. After doing some research I came up with the following design but am looking for any input or feedback before I dive in.

The crosshatched shaded in parts are perforated tube. I will stuff /wrap some stainless steel wool packing in a couple areas but I'm not sure which yet, also I'm unsure about the little v shaped peice on the left.

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1967 Bug ( the daily rod )
1964 Fury Wagon ( the pavement shredder )

[modok]

No less than three chambers to avoid drone. Check

Four into one header using a long collector length, I have had best results with LONG muffler with perforated tubes, the inlet tube perforations running over 18 inches and being more gradual.
Works better than a long tube with a short/fat muffler at the end.
Short muffler for short collectors, long muffler for long collectors... Kinda makes sense IMO
But I have not found a way to use long setup on sedans.

But on my tri-y the inlet tube of the muffer is just a short shub. It does not need a long collector length. At least not the way it's tuned now.

HIGH performance system that comes out the cutouts! WOW
I think it's impossible, but don't let me stop you from trying.

[allamaabroad]

From what I've read, steel wool isn't great for muffler packing, even if it's stainless. May want to double check that, but you may be better off with a purpose built muffler packing material (4 stroke dirt bike muffler packing, pretty nice stuff)
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Dennis - 1973 Super Beetle ('16-'21)
Debbie- 1970 Baywindow Bus ('21 - Present)
Tin top camper/adventure bus

2180 TW: CNC Panchitos, Beehives Done Right, Web 163, Ultralight Lifters, 1.3 Rockers, CSP Python, Custom Speeduino EFI Conversion with 40mm Throttle Bodies

Distributors are lame

I have a really hard time leaving things alone...

Innovative and affordable engine management systems and EFI conversions for your Vintage VW
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[evanfrucht]

[modok]

Packing absorbs higher frequencies but does not do anything for low frequencies. IMO it is the low frequencies that are annoying to hear.

Carbon itself also absorbs high frequencies.
A muffler with zero packing will sound a bit tinny at first, but that tones down with time as the carbon builds up inside.
A bit of fiberglass in there might even that out, if it blows out at the same rate the carbon builds up

[67 Sunroof]

Man that’s crazy! Making your own muffler!!!? I hardly knew that was in a muffler?
I used to have a very expensive “Trust” brand muffler with an anti-reversion chamber I think it was called. It had the exit go back around the side of the muffler and then enter it AGAIN!?
What would that do?
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1776cc, CB crank, CB 2241 cam, CB light lifters, CB H-beam rods, CB light flywheel, Mahle forged pistons, A1 Sidewinder exhaust, Dellorto drla 40’s, Hoover modded case, fully balanced, fully flowed, heads by www.type-emotorsports.com, Air ride suspension by https://www.airkewld.com/?Click=3989

[Wreck]

It has a small chamber muffler ,then a glass pack at the end , it’s still louder than I’d like .

[evanfrucht]

[67 Sunroof]

Man that’s sweet looking.
I guess it wasn’t an anti reversion chamber muffler. It was on a Comptech header I had but works for mufflers as well.
You can also “step” headers....start smaller and gradually step the diameter up a tad to produce more torque I think?

https://crateinsider.com/using-anti-reversion-to-create-free-power/

Here is a similar design..

And more...just giving you some ideas....

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1776cc, CB crank, CB 2241 cam, CB light lifters, CB H-beam rods, CB light flywheel, Mahle forged pistons, A1 Sidewinder exhaust, Dellorto drla 40’s, Hoover modded case, fully balanced, fully flowed, heads by www.type-emotorsports.com, Air ride suspension by https://www.airkewld.com/?Click=3989

[hendersoned]

I have built a number of 2 chamber mufflers with no stuffing/packing. I used 16 ga. galvanized sheet and cold galv paint on the welds. I used bent deflectors and kept all the holes/passages that same size as the exhaust (2") for an off road car, not too loud but i drive it offroad...

[modok]

the only real problem is that you build it special enough, you will not be able to buy a replacement.
If it is a prototype that does not work out, then it's no problem, but it if DOES work.
That means you will have to fix it when it rots out.

And the motivation is hard to find.

So the only solution I can see.... is change the design to a new experiment, and let the cycle repeat until you end up building a different design that works good again.

[jpaull]

With 1 muffler you will always have that piece of crap high pitched whistly sound in the upper rpms that VWs make. No matter what you do it will be there. It might sound decent inside the car but outside it sounds crappy. I have seen some of the most famous vw pioneers driving their hotrod vw going through the gears with their fat boy style muffler whistling away fart canning it up and they think its cool. The exhaust speed is so fast cause the muffler is so close, And its a 4 cylinder. Having multiple mufflers like wreck shown is good, or split into 2 mufflers. Just want to give u a heads up before you spend 30 hours on the 1 muffler and it still has the disappointing attributes.
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[email protected] MPH 1/4 Mile & 8.1 @ 83.7MPH in 1/8 Mile with Mild Type 1 VW Mag Case 2234cc commuter engine in stock weight bug w/only .491 total lift(CB2292 Cam), 42x37 heads, 48idf's, Street tires, Belt on, Mufflers, Pump gas, video of the run here: https://youtu.be/M3SPqMOKAOg

Transmission by MCMScott:
Rhino case, Klinkenberg 4.12, Superdiff, 002 mainshaft with 091 first idler. Weddle 1.48 Third & 1.14 Fourth.

[Tvättbjörn]

To find out if your muffler / exhaust design is any good you will have to run the car on a dyno after every single change on the system. You can gain / lose a lot of HP and torque depends how the system is set up. Chamber sizing and the internal layout makes all the difference. Ask me how I know

[evanfrucht]

[evanfrucht]

[evanfrucht]

Well, I'm done for the night. Thanks for the input everyone, keep it coming!

I'm going to wrap up this burrito in the morning

_________________
1967 Bug ( the daily rod )
1964 Fury Wagon ( the pavement shredder )

[67 Sunroof]

Looks cool. Interested to hear what you think of it!
_________________
1776cc, CB crank, CB 2241 cam, CB light lifters, CB H-beam rods, CB light flywheel, Mahle forged pistons, A1 Sidewinder exhaust, Dellorto drla 40’s, Hoover modded case, fully balanced, fully flowed, heads by www.type-emotorsports.com, Air ride suspension by https://www.airkewld.com/?Click=3989

[GS guy]

In my dabblings with muffler design (for a 2-cyl motorcycle) and schooling from an old friend who did extensive testing on mufflers for model aircraft engines - the bigger you can make the muffler, the quieter. I think if you really want to see what a "quiet" muffler should look like inside, find a "throw away" Acura RSX Type S OEM muffler and take a look inside. Quiet, yet allows that 2L to rev to 8K and produce 200hp! It is fairly large, but must be well engineered to match the high performance engine (along with the mid-pipe resonator).
It looks like your flow path requires the gasses to pass through the wool - I'd avoid that in the end sections. That wool could clog up with carbon? Also make sure the flow-path perforated sections (primarily the cones) have at least equal open area to your pipe ID. Perforated metal typically has about 50% open area relative to the size of the sheet.
Seems like the 2-muffler set-up shown previously would be the quietest (more muffler volume). If growing my own I'd be tempted to fit a resonator (straight through) for the first muffler, then a larger (choose your brand) performance muffler for the 2nd.
Jeff
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70's vintage Deserter GS buggy - undergoing transformation to Super GS!

[jpaull]

[raygreenwood]