2 strokes really need a expansion chamber?

[oscaryu1]

This is what I currently have:

This is what I'm thinking of getting:

$27


Or should I get this?

$36


Or this?

$40


Or top of the line?

$40

 

[Kaptain Krunch]

For what engine?

 

[oscaryu1]

This is for a 49cc 2 stroke "pocket bike" engine... remember... they do NOT flow ALOT of air...

Modifications:

"Racing" carbuertor -

(That)

10 degrees advanced timing
"Full circle" crankshaft -

(Lol... it's not billet)

And a billet air filter adaptor + "K&N" Clone filter, NO2 injection, ported intake/exhaust, fibreglass reeds...

Is it worth it to get a nice exhaust system for this 49cc engine?

 

[Kaptain Krunch]

If its running fine now, i personally wouldn't put any money into it, but thats just me.

 

[Affair_driven]

The correct expansion chamber can do more for a 2 stroke than an any other single modification. Emphasis on correct.
Takes a lot of math to get it right for a particular engine.
Can be a backwards step if designed for a different engine than what you currently have.
In other words, make sure it's matched to your engine.

 

[oscaryu1]

The correct expansion chamber can do more for a 2 stroke than an any other single modification. Emphasis on correct.
Takes a lot of math to get it right for a particular engine.
Can be a backwards step if designed for a different engine than what you currently have.
In other words, make sure it's matched to your engine.

What do you think is the best for me?

 

[jr dragster T]

I'd probably go for the 3rd or top of the line.

 

[Affair_driven]

No clue.
Ask the manufacturer. All it takes is an e-mail or phone call.
Trial and error would be an expensive option.

I'd probably go for the 3rd or top of the line.

Based on what?

 

[BradenM]

3rd or top of the line-I agree, based on that fact that option 1 and option 2 have small cylindrical sections and are located closer to the exhaust flange. This means those pipes are tuned for lower RPM function-expansion chambers only work in narrow RPM bands. The latter 2 however have larger cylindrical sections, further away from the exhaust flange, meaning that option 1 is likely tuned for 8-9000 RPM range and the last is about 9-10,000 rpm. A properly built pocket bike engine WILL spin 12.5k at redline.
I cannot cite any sources other then Town and Country exhaust in North Geelong, Victoria, Australia, and my own understanding gained from them. This is a result of 3 years worth of learning.

 

[BAMBY]

oscaryu1,
i dont know if those pipes are even tuned to your engine or not...
i do know that they are not a necessity, however, they do make a conciderable differance in efficiency and performance... as the whole point of the expansion chamber is to make the sound waves echo and pull the next exhausts stroke's exhaust out... sort of a scavenging affect.

check out this online java app. maybe it will help you pick out a pipe or help you make one.

http://www.mh-aerotools.de/airfoils/javapipe_en.htm

in any event, i would just make sure you do your research before you buy... it'd suck to be stuck with nice pipe that dont help your perf.

good luck,
BAMBY

 

[Affair_driven]

Escaping unburned fuel is what the system is designed to recover.
http://upload.wikimedia.org/wikipedia/commons/5/52/Arbeitsweise_Zweitakt.gif

 

[BAMBY]

Affair_driven... you are right... it is a combination of things
its hard to explain kinda... also crams as much air/fuel mixture in combustion chamber as possible

 

[lemegacool]

BUY A BOOST BOTTLE!!! i got one on mine and WOW i smoke all my friends with my machine... event the one that putted 800$ worth of mods in it...

list of mods i done to it

i have the second exhaust you listed on it ... came with it stock...
- stock gear ratio
-aluminium high compression head kit (i blew the stock one)
-racing mikuni-style carby / kn airfilter
-BOOST BOTTLE!

thats it! and i got IMPRESSIVE acceleration WAY better then before and the engine runs smoother at idle...

 

[oscaryu1]

BUY A BOOST BOTTLE!!! i got one on mine and WOW i smoke all my friends with my machine... event the one that putted 800$ worth of mods in it...

list of mods i done to it

i have the second exhaust you listed on it ... came with it stock...
- stock gear ratio
-aluminium high compression head kit (i blew the stock one)
-racing mikuni-style carby / kn airfilter
-BOOST BOTTLE!

thats it! and i got IMPRESSIVE acceleration WAY better then before and the engine runs smoother at idle...

I honestly think it's utter... bull... squat.

Think about it. All it is is a hole cut in an manifold... a piece of tubing... and then a CO2 like bottle.

And I honestly don't get how it works. There's already air in that bottle, ect, so theoretically, the CARBURETOR creates so much "air/fuel" mix, that it pushes INTO the "boost bottle", which is already FULL... so it's compressing that air too?

And that little tiny 49cc carburetor can move that much air fuel mixture to actually compress what's left in the bottle?

And when it's "sucked out", it's a dang metal CANISTER. It's not going to flex to make up for the lost air.

So theoretically, I get the CONCEPT, but the item itself makes no sense whatsoever.

 

[EagleTalons]

I prefer the boost balloon filled with acetylene.

 

[oscaryu1]

No no no n00bz, 100 pound NO2 injection with direct injection

 

[jr dragster T]

No one makes a 100 pound nitrous tank, Direct injection? Good luck with that.

 

[lemegacool]

well when i pinch the tube that goes to the manifold the engine stalls...

 

[crazycart]

My guess is your "boost bottle" is leaking and its just leaning the engine out, making more power.

 

[lemegacool]

well it's perfectly sealed sooo i guess it's a mystery how i ended up with more torque...