Silencing a motor with the exaust

[DBaker]

I have a 8 hp tecumseh engine and want to silence the exaust. Anyone has any idea of exhaust pipe design that could do that?

Thanks!

 

[Jake.B]

The stock muffeler?

 

[Doc Sprocket]

If you want it quieter, get a muffler with a larger chamber than stock. You cannot "silence" it completely.

 

[DBaker]

Jake B :Yes it's the original muffler, here's a picture of it, it's about 1.5" thick, 6" high by 2.5" wide.

toystory_4wd: what do you mean by larger chamber? can it be something i can make? i've seen a muffler made with a pipe and a spray paint can on this forum, would this kind of design work if I use something a bit bigger than the spray paint can as the chamber?
I'm aware that I won't be able to completely silence it but I would like to silence it as much as i can.

 

[souperman000]

the chamber is the same chamber as your car would have for a muffler. A bigger area inside the pipe before the gas exits through the exhaust pipe. (soory if it doesnt make sense cant explain it well enough)

 

[DBaker]

OK . then is it more something like in A where the air passes through the pipe and uses holes in the pipe to transfer some of the noise in the larger chamber
Or as in B where it only travels through a larger chamber, and this would be enough to silence it?

 

[Doc Sprocket]

You're dang right you can make one! Here's the Cherry Bomb that I made myself-

http://www.diygokarts.com/vb/showthread.php?t=7449

 

[Doc Sprocket]

They would both work. i think "B" would be a bit quieter. If you take "A" and put a stop in the middle of the pipe (literally, a solid piece of metal that nothing can flow through), then you basically have my muffler. The gasses enter the inlet pipe and travel to that stop. The stop forces the gasses to go thru the holes into the chamber. The gasses fill the chamber, and in order to exit, must pass thru the holes out the other side.

 

[OzFab]

They would both work. i think "B" would be a bit quieter. If you take "A" and put a stop in the middle of the pipe (literally, a solid piece of metal that nothing can flow through), then you basically have my muffler. The gasses enter the inlet pipe and travel to that stop. The stop forces the gasses to go thru the holes into the chamber. The gasses fill the chamber, and in order to exit, must pass thru the holes out the other side.

If you also use some fibreglass wadding (roofing insulation) between the two pipes it should muffle it a bit more

 

[Brandon1023]

Every time this question is asked, there's always that one person who says "Use the muffler that came with it." No. If you know what you're doing/have access to adequate materials, you can do pretty much anything. Also, pointing the end of the exhaust downward (towards the ground) it's supposed to muffle it somewhat rather than amplifying the sound waves being projected. If you think about it, these are air particles which are crashing in to eachother at a high rate. This is what causes mechanical noise. If you have a bunch of little obstacles for these air particles to hit, they slow down. And the more the slow down, the less noise these waves make when they leave the muffler. Hope this explains a little bit more.

*IF the muffler has SO MUCH restriction, the engine won't perform well. But as for the people who say "Nah man.. Run it open pipe, you can get like 30 more RPM!!!!," I'd rather sacrifice a little bit of performance than annoy all my neighbors and have people give me dirty looks while I ride around. I live in the suburbs of Miami, FL where houses are ~10 feet apart.. so that's also another reason. Hahaa.

On a side note.. Can anyone tell me why is it that an engine with a single 420cc cylinder makes at least 5x more noise than a 3,500cc car engine divided in to usually around 4-6 cylinders?

 

[Doc Sprocket]

On a side note.. Can anyone tell me why is it that an engine with a single 420cc cylinder makes at least 5x more noise than a 3,500cc car engine divided in to usually around 4-6 cylinders?

Sure!

*Multiple feet of large diameter pipe
*A muffler with a very large chamber
*A catalytic converter with a very large chamber
*possibly a resonator
*A mechanically quieter engine
*An exhaust system that is often mechanically isolated (rubber hangars and a flex joint

There's probably more.

 

[Jake.B]

Yeah thats about all of it^.

 

[kendelrk]

maybe get a thick and large box sort of like a converter in a car exhaust and put that on a large diameter pipe coming from the engine, and then on the opposite side put another pipe point straight down but not to close to the ground, i mean have you ever heard how quiet those mini quads are?

 

[Brandon1023]

Haha that explains it. I knew there was a legit explanation, but I just couldn't wrap my mind around it.

 

[DBaker]

Thanks a lot for all your answers guys!

I also searched the net to dig further into the question and came across this page with cut view of a couple muffler designs

http://www.paraglidingteam.nl/PPGTechnics/sound and noise/Mufflers/1155795969.pdf

 

[DBaker]

followup on the making of the muffler

I've decided to go complicated on the making of the exhaust pipe.

Here are the pictures of it before I weld the capping on. I know my welds are very poor but i'm not quite used to stick welding sheet metal !

 

[Brandon1023]

Wow looks like a car muffler. So how much better does it muffle the sound as opposed to the stock muffler? Was it worth building?

 

[tundrabeagle3]

that looks pretty cool. did it affect your motor performance?

 

[exenos]

I definitely agree, ARC welding sheet metal is not fun. The muffler look like it will work great, now we just need a video of it.

 

[DBaker]

The capping hasn't been fabricated yet and i'm having a baby this weekend so I won't be able to work on it for a couple of weeks. But i'll post a video and confirm if there is a loss of power as soon as I know!!

Got any tricks on stick welding sheet metal? Or what type of rod to use?