Muffler/Expansion Chamber - Making One

H

Hive

Guest
Okay! Not sure where to post this one, so will stay with similar drive type, though this may apply to other applications and engine types.

It is 0 degrees F where I live, bike is hanging, motor is tucked in corner. Fishing is kaput. I would be hunting but too cold and not in mood. Besides, no respectable grouse or pheasant would be out in this weather, so, before I get into the darkroom, here is the plan.

Construct a "muffler" or small expansion chamber for next season. All suggestions/critiques are welcome, particularly from those who have tried a similar project.


Motor is 2-cycle T-3300 on GEBE rack system.

Use a 3/8" copper elbow from exhaust pipe - it fits and is easily clamped tight after cutting slits in one end to secure;

Attach high-temp silicone tube to the elbow;

Connect that tubing to 6" piece of 2.5" PVC - the "chamber;"

The "chamber" or muffler will be empty (as opposed to a holed out pipe or silicone and/or surrounded with SS wool inside)

Exit end is .5 inch.

Paint black.

Fasten chamber downward to GEBE rack mount, redirect exhaust away from bike.

Will this rig reduce exhaust noise and not harm engine or reduce efficiency?

 
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A

andyinchville1

Guest
Hmmmm...somebody else here used copper in their exhaust system....Can't remember off hand....their solder joint melted....so if you use copper have to clamp or use a spring system to keep it all together..sounds like you might be doing that since you mentioned the high temp silicone hose..As far as PVC and high temps....Not sure....but gut feeling is that it may melt?....I could be wrong tho but PVC is basically like a plastic....and probably not a high temp tolerant one at that...but if it is far enough downstream maybe the exhaust will lose enough heat so as not to melt it?
Anrew
 
H

Hive

Guest
Copper Exhaust Failure

That was moi. I assumed it would fail, but had to see how long it would take. Not long. I removed the thread, fearing someone would try it and have an accident ...

The first connection melted and dropped the pipes. Just glad it did not hit a car, etc.

That is why only copper will be first piece attached to engine pipe and no solder employed.

May have to use copper instead of PVC for the chamber to gain a heat sink, but silicone will be employed and clamps will connect the components physically this time.
 
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J

JemmaUK

Guest
When I set up the Exhaust extension on my old bike I used a .140 aero engine bend to connect to the exhaust port... that was fine regarding temperature...

From what you have said about the plan so far it sounds good - it *might* given you will have created a stinger, provide a little bit of power boost but I'm not sure..

Im curious about the performance of your engine. I just got the T3300 and as far as top end and fuel consumption I am not entirely impressed...

Jemma xx
 
K

kerf

Guest
Tin based solders won't handle the heat close to the exhaust port but phosphorous copper brazing will. The melting temp is 1400 F, so you need at least oxy/mapp to get the job done. The rod uses no flux, just sweat as you would with tin.
 
H

Hive

Guest
Tin soler

Yes, Thanks. I found that out the hard way. I will use a ss clamp to connect to pipe and then clamp silicone tube to that elbow and go from there.

Sound good?

All I have to do is acquire the silicone tubing.
 
H

Haggard

Guest
Hi Hive . Your on the right track . Exhaust can make or breaka 2 strokes performance . I'm trying to think of the term I heard used.
. Harmonic charger? Harmonic boost maybe?
I've done an extreme amount of reserching aswell as hands on trial and error and while I cant tell you excactly what length , what width what degree etc ,No one can without having the actual motor in there hand , I can give you a good thorough understanding of the principles involved but be warned, once you delve into this misterious phenominom . It'll be spring before you know it!!. Keep an eye on the Mounting a pocket bike thread in rack mounts. I'll be doing a complete section on 2 stroke exhaust that i guarantee to answer all your questions : )
cya
 
H

Hive

Guest
I Will

Be looking forward to it.

I right now I have concluded that the chamber, given the fact that the exhaust is just open pipe otherwise, it must be such that it does not create too much back pressure.

Figure a 6-incher will do it, with a 2-inch diameter.

Spring! I wish!
 
H

Haggard

Guest
You can see a working model of a stroke expansion chamber on "my space"
http://bikesntrikes.spaces.live.com/default.aspx

It demonstrates why the length of the header and the size and angles of the expansion chamber have to be directly perportionate to the cylinder size and port timing has to be taken into consideration aswell for ultimate performance

~Haggard~
 
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H

Hive

Guest
Expanion Chamber

Great video, Haggard. Thanks!

I knew these things have a science behind them but decided not to get too big with extractor device, not going for speed.

Planning to go with a gradually opening pipe diameter, so any restriction is minimal.

Using .75 copper pipe I had laying around, may go to one-inch.

The inside is 5/8", which is larger than the engine exhaust pipe. If 1" will use .75 inside pipe but make it shorter.

The inner pipe will have lots of orderly drilled ports (holes) and is longer than the outer pipe, to accept the silicone hose from exhaust port.

The inner pipe extends just a bit from rear of pipe with gaps around it to increase flow - decrease resistance.

I was going to stuff area between two pipes with fiberglass roving, but may forget the roving in this first version or only fill one-half of pipe - a mini expansion chamber?

The roving will deaden sound and not deteriorate and float away, according to the information on the "Swedish Exhaust Pipe" link for straight-through exhaust muffler on 4-cycle airplane power, here: http://www.piteraq.dk/flight/muffler.html

May build second version with roving, if first causes problem or does not work and even third to experiment a bit just for fun.

I wish to deaden sound a bit, without the bulk, and without hindering flow, which is why the larger pipe. Engine exhaust for is only 3/8". A 3/8 copper elbow is clamped with SS hose clamp and a silicone hose connects the elbow and the muffler.

Will keep all posted with pics etc. but will likely begin separate thread on it, so look for it when I can test the device.

Appreciate the video you linked - and other vids also. Thanks again.
 
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