How to build a muffler

[D8R]

Have looked at net about this topic but normaly only get info about how to take away low base tones. That´s oposite of what I want to my CAT D8.
Engine is a 4-stroke Honda GX100 and space available is
width 5 1/2"
lenght 4"
height 4"
exhaust dia is 22mm (scale)

Any suggestion before starting cutting steel? Weight is no issue here so it can be built with thicker walls if needed.

Dan

[foub01]

You could probably manage to make it run without much noise pretty easilly in that space but it wouldnt be very easy to make it sound like the real thing.i think it will always sound like a lawnmower

[Smokin Joe]

A muffler or for that matter, anything beyond the exhaust port of the head, would not duplicate a particular sound.

A major hurdle is 2 stroke vs 4 stroke. I wish you the best of luck.
Please keep us posted.

Joe

[fhhhstix]

Both you engine and the D8 are 4 stroke engines. The size and number of cylinders will be the biggest difference. Here is an article I found on exhaust tuning and from what I read the length of the exhaust, distance between the chambers, and flow will be the deciding factors on the sound.


Though the main part of the exhaust note is determined by the mufflers, resonators, catalytic converter and pipe diameter, there are a few factors that affect sound at the tip. Tip size actually has very little to do with sound, unless you go to a much larger or smaller diameter. Smaller diameter pipe will restrict the engine, slowing the exhaust stream and decreasing engine noise, and a larger diameter tip will make the engine louder only if the original tip was a restriction.

Down-turned tips, particularly those that dump underneath the car, can deepen the exhaust note by bouncing sound off the ground and using the undercarriage as a resonator. The ground will absorb much of the annoying high-frequency sound from smaller displacement engines.

The only way to significantly affect exhaust register is with a tunable tip, such as those manufactured by SuperTrapp. These tips (originally designed for ATVs and dirt bikes) use conical or disc-shaped inserts to both alter the wavelength characteristics of the escaping exhaust and suppress the flames emitted by very short exhaust systems. These tips allow the user to tune the exhaust note slightly by inserting or removing disc spacers that act as a secondary muffler. This is the most effective option for exhaust note tuning, but considering the fact that they cost 10 times what the average tip does, it may be cheaper to just purchase a new muffler.


Length



On applications where it is possible to do so, like motorcycles and ATVs, lengthening the pipe by as little as 6 inches can drastically affect exhaust note. Doing so gives high frequency waves more opportunity to cancel out, allowing the long, low frequency waves to escape.


I hope this helps.
Travis

[D8R]

Thanks for the input.
I will set up engine (not ever started it yet) and start with some telescoping tubing to see what lenght means to sound. maybee the idee of building it square is bad, But the space limits the possibility to build a muffler like on motorcycles.
My first idea was to have the box as outside limit and try to make an inside with different walls, making the exhaust travel upto 4 times inside the box.
I´m well avare that the sound of a 3406 can not be duplicated this way but I do not want the "lawn-mover" sound!
Will keep you updated, any more info velcome
Dan

[foub01]

your idea of deviding the box up into sections would work if you put the pipes through at at staggered points with packing in each section would probably be your easiest option.bad drawing but hope this helps a bit
http://i1269.photobucket.com/albums/jj584/foub01/silencer.jpg

[doodlebug]

Just got this link via email http://www.mytractorforum.com/showthread.php?t=227730
Hope it give's you some more idea's.
Cheer's, Neil.

[D8R]

Thanks all for comments and useful info.

Did start buildning the muffler today, with a curculare design instead of box.
http://i1014.photobucket.com/albums/af270/gulalastbilen/DSC_0090.jpg
http://i1014.photobucket.com/albums/af270/gulalastbilen/DSC_0089.jpg

This tread will be closed and all findings when building the muffler will be found in my building tread:

http://rctruckandconstruction.com/showthread.php?p=54696#post54696

Can wait to get it done and start the engine.
Promise to post a youtube later!
Dan