Can we fabricate our own expansion chamber?

G

gone_fishin

Guest
for real. i see that a few of you know the theory behind expansion chambers. i can understand it when it's layed out for me. i saw it on here somewhere...anyway, maybe it's possible to make a decent one on our own?

IF all i had to work with was my current down-pipe & muffler, would it be possible to construct a primitive series of nozzels/cones/whatever that could be placed in the muffler? could someone do the guesswork needed to make the project worth trying?

better-than-nothing technology is what i'm after here.
 


G

gone_fishin

Guest
i got it jaker, thanks, that's an interesting site :)

it looks great, but i'm still lost...maybe someone who's already hip to pipe theory could have a look and give us the basic values needed to get a calculation?

see, my 70 has about 350 miles on it, new plug, 36:1 pre-mix, full breather intake, 3rd notch on needle. at topend, which is strong, i can tell it could do a bit more if i had the "pulling" effect of an expansion pipe.

anyway, i'd love to see this project take flight...i'd really appreciate someone piping in (pun intended) 8)
 
S

Steve

Guest
Augi,

I obviously have no experience with tuned exhaust systems on these engine, but I do have experince with them on other 2 cycle engine, all R/C model engines. What I have learned about them in general, is they provide more power, however it is at the one RPM range where they are tuned, and always at the expense of torque at lower RPM ranges. They can be tuned for a more broad RPM range, but then the gains are less.

I guess what I am trying to say is, unless you want all out power in one RPM range for racing and such, IMHO a tuned exhaust on one of these bikes is not a good deal. I would think a good free flowing exhaust is what we really need.

Just my opinion on the matter.
 
C

chieflets

Guest
you would want something with mid to top end unless ur doing allot of hill climbing u would want bottom to mid range torque i guess

Chieflets
 
G

gone_fishin

Guest
Steve: yup, that's what i thought i remembered...thanks for that...time to go for unrestricted exhaust, i've already cut the inner pipe all the way off, maybe i should widen the outlet too?

i have to take a 5 mile ride in just a few minutes, i'll take the bottom of the muffler off & see what happens.

however...i fully intend to enter into the realm of MotoredBike racing, this topic will stay alive.
 
B

Barret

Guest
augidog said:
i have to take a 5 mile ride in just a few minutes, i'll take the bottom of the muffler off & see what happens.
About that...I actually don't have much of what you would call a muffler any longer, as mine rattled loose while ridding one day, and it suddenly gave me a stronger push and a bit more power. I only have the "inner muffler" on, and not the outer shell [pic below]. After riding like this for a while, I checked my spark plug for too rich/too lean mixture, and it's never been either direction. I've never looked back, and no one has complained about the noise level yet. I don't ride it after 9 p.m. or at the butt-crack of dawn, and there are other kids in the neighborhood with loud toys of their own (mini-bikes, homemade scooters, etc.). I love the way it rides now.

http://i84.photobucket.com/albums/k9/barret_31/000_0002-1.jpg
 
P

pianoman8t8

Guest
what exactly does an expansion chamber do? i have no idea about what these do...

-pianoman
 
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