4stroke pipe on a 2stroke

[backwoodsracer]

Some one answerd this for me few years ago but what would happen if you took th fatty off and put a reg 4 stroke pipe on or vise versa?

[Brauap]

I have always wondered this and wanted to experiement but I simply do not have the $$$$ to do so! hah

I think a 4T pipe on a 2T would create massive torque because if you look at all the trials bikes that is the kind of pipes they have.. I am not sure a 4T could run on a 2T pipe due to the small exiting hole, unless it was either a small bore 4T or you modified it. But I think it would be create lots of top end power.. but I'm not sure on either! haha It would be fun to experiement on though!

[Honda#4]

Some one answerd this for me few years ago but what would happen if you took th fatty off and put a reg 4 stroke pipe on or vise versa?

It will sound like it has two extra strokes of power LMAO!:D

[wilkin250r]

2-stroke pipes are very particular in design. The fat section of the pipe is very crucial in creating power, it helps to remove exhaust gas, but probably more important, it helps keep the fresh fuel/air mixture inside the cylinder instead of letting it escape out the exhaust port.

A 4-stroke doesn't need this because it has valves. The exhaust valve closes, and that's what keep the fresh fuel/air inside the cylinder, it doesn't need a pressure wave coming from the pipe.

[honda400ex2003]

braap ding ding ding. braap ding ding ding...


sounds like a winner to me. who needs an expansion chamber.


steve

[ZeroLogic]

Originally posted by wilkin250r
2-stroke pipes are very particular in design. The fat section of the pipe is very crucial in creating power, it helps to remove exhaust gas, but probably more important, it helps keep the fresh fuel/air mixture inside the cylinder instead of letting it escape out the exhaust port.

A 4-stroke doesn't need this because it has valves. The exhaust valve closes, and that's what keep the fresh fuel/air inside the cylinder, it doesn't need a pressure wave coming from the pipe.
Exactly, it will not work.;) The motor will run but it will have no power.

[jcs003]

two stroke pipes are tuned by trial and error for specific applications. i.e. XC racing, MX, drag, duning...etc.

a race two stroke engine probably has triple the time invested in R&D for pipe, port, carb and intake than any four stroke race engine.

cam design can be done solely with a computer program. port layout isnt necessarily done in a fundamental fashion. some guys do it just by experience through R&D. others, take info from a computer and apply with simple rotary tools.

all this is playing a role in two stroke pipe development. on a four stoke it basically comes down to diameter and type of silencer clambering a pipe is using.

[krt400ex]

Originally posted by wilkin250r
2-stroke pipes are very particular in design. The fat section of the pipe is very crucial in creating power, it helps to remove exhaust gas, but probably more important, it helps keep the fresh fuel/air mixture inside the cylinder instead of letting it escape out the exhaust port.

A 4-stroke doesn't need this because it has valves. The exhaust valve closes, and that's what keep the fresh fuel/air inside the cylinder, it doesn't need a pressure wave coming from the pipe.


couldnt have said it better. without an expansion chamber, a kx250 will run like an xr100

[Brauap]

How to the trials bikes run?? I honestly do not know.. is it all in the porting?

[wilkin250r]

I don't know about all trials bikes, but I know the Gas Gas is a popular one, and it's a 4-stroke. It LOOKS like a 2-stroke because it's a side-valve engine.

[Hondamaster5505]

Alright, think of a two-stroke pipe as a "turbo"

On a 2-stroke, it will run with a regular header. BUT, will NOT make much power and will barely have a "powerband" (The sweet spot in the motor where it comes to life)
It's all part of the sonic wave theory. Basically the cone shape at the end of the pipe, takes the exhaust and makes a sonic-wave type deal, back towards the cylinder. This forces the extra un-burned air and fuel back into the cylinder before the combustion.
When the timing of the pipe (wave) and motor match up perfectly, this is where you experience that "powerband" feel. Everything is timed perfectly.

Powervalves help change the timing of this wave and how it enters the cylinder giving it a broader power range.

On a 4-stroke, an expansion chamber is not necessary. The exhaust valves seal off the cylinder from much excess escaping from the motor. All the wave would do, is bounce of the valves. It wouldn't be able to force any air back into the motor.

Hope I explained it clearly.

[BoneStockHonda]

I got the impression that he was just talking about switching silencers :huh ...

[Brauap]

Wilkin.. they had just come out with the 4T trials bikes.. they have been 2T's for many many many years! Both 2T and 4T trials bikes have similar pipes..

And Eric.. very very nice explanation!! ;)

[jcs003]

Originally posted by Brauap
Wilkin.. they had just come out with the 4T trials bikes.. they have been 2T's for many many many years! Both 2T and 4T trials bikes have similar pipes..

And Eric.. very very nice explanation!! ;)

if you look close at a 2-stroke trials pipe it kinda curls at the exhaust manifold and increases diameter(slightly). when it goes out towards the rear it looks like a fat four stroke pipe. this, in actuality is a design specific for the trials bike power output. its more for creating torque and allowing use of power in the lower RPM ranges.

basically you cant rev out a two stroke trials bike. if you could it would have a big bubble in the pipe.

[wilkin250r]

Apparently I'm just not up to speed on the trials segment of the offroad community. I can't know EVERYTHING. :p

[jcs003]

Originally posted by wilkin250r
Apparently I'm just not up to speed on the trials segment of the offroad community. I can't know EVERYTHING. :p

you do know alot though. you helped me out on plenty of occasions.

[backwoodsracer]

Originally posted by Hondamaster5505
Alright, think of a two-stroke pipe as a "turbo"

On a 2-stroke, it will run with a regular header. BUT, will NOT make much power and will barely have a "powerband" (The sweet spot in the motor where it comes to life)
It's all part of the sonic wave theory. Basically the cone shape at the end of the pipe, takes the exhaust and makes a sonic-wave type deal, back towards the cylinder. This forces the extra un-burned air and fuel back into the cylinder before the combustion.
When the timing of the pipe (wave) and motor match up perfectly, this is where you experience that "powerband" feel. Everything is timed perfectly.

Powervalves help change the timing of this wave and how it enters the cylinder giving it a broader power range.

On a 4-stroke, an expansion chamber is not necessary. The exhaust valves seal off the cylinder from much excess escaping from the motor. All the wave would do, is bounce of the valves. It wouldn't be able to force any air back into the motor.

Hope I explained it clearly.


thanks DMC

[mineralgrey01gt]

Originally posted by Brauap
How to the trials bikes run?? I honestly do not know.. is it all in the porting?

probably to do with that and possibly the powervalves have something to do with it. I know you can have adjustable powervalves

[BoneStockHonda]

Originally posted by Hondamaster5505
Alright, think of a two-stroke pipe as a "turbo"

Good explanation but no I will not think of an exhaust as a turbo. Nothing alike....

[Ruby Soho]

Originally posted by BoneStockHonda
I got the impression that he was just talking about switching silencers :huh ...

me too.:p

[Hondamaster5505]

Originally posted by BoneStockHonda
Good explanation but no I will not think of an exhaust as a turbo. Nothing alike....

Never said it did the same thing as a turbo. I said that as in, the pipe's wave pretty much forces the unburned and excess fuel & air back into the cylinder and actually raises the compression when this happens.

[250R-Dee]

If the 2-stroke motor is of the rotary valve variation you might be able to get away with using a thumper pipe.

Research: Kawasaki A1 Samurai.

Swapping the silencer on a 2-smoke motor that has a expansion chamber with a silencer from a thumper will change the dynamics of the exhaust which in turn will lead to a power loss. There's a reason why nobody is doing this swap.