2-stroke pipe on a 4-stroke?

[bluerider125]

okay i dout if this goes here but ive got a few questions.

1) what is the expansion chamber for on a 2-stroke? i figured for better exhaust flow since theres twice the exhaust than on a thumper, but it goes right into a teeny little pipe and then the silencer. is it big so it cools the gases so it doesent melt the pipe or what? im confused. :think:
2) what would happen if you put a 2-stroke pipe on a thumper? id bet it would sound pretty interesting! :p

thats it for the q's, bluerider125 out:confused:

-Rob

 

[Vic]

From Eric Gorr's website (yes, it's English):

The exhaust pipe of a two-stroke engine attempts to harness the energy of the pressure waves from combustion. The diameter and length of the five main sections of a pipe, are critical to producing the desired power band. The five sections of the pipe are the head pipe, diffuser cone, dwell, baffle cone, and the stinger. In general, after market exhaust pipes shift the power band up the rpm scale. Most pipes are designed for original cylinders not tuned cylinders. Companies like MOTOWERKS custom computer design and fabricate pipes based on the cylinder specifications and the type of power band targeted.

 

[Adrenaline]

I totally understand what Eric said but why don't companys put an expansion champer on four strokes? it would harness the pressure waves from combustion. Wouldn't that increase tunibility and power?

 

[LWilson250]

Originally posted by Adrenaline
I totally understand what Eric said but why don't companys put an expansion champer on four strokes? it would harness the pressure waves from combustion. Wouldn't that increase tunibility and power?

Simple, they don't need them. An expansion chamber on a 2-stroke is essential to the operation of the engine.

On a 4-stroke you do not need the sonic back waves because the engine uses valves.

On a 2-stroke when the spark plug fires and the piston is forced down the fresh fuel is pushed up from the crankcase through the ports. The hot high pressure exhaust that is forced out expands and then is compressed in the pipe and sends a sonic pressure wave back towards the cylinder, this pressure wave helps to ensure the fresh air/fuel mixture is held in the cylinder.

A 4-stroke does not operate on the same gas dynamics as a 2-stroke. It uses valves to control the exhaust process. The air/fuel mix is sucked into the combustion chamber and compressed, ignited, and then forced out the exhaust valve.

Go to http://www.howstuffworks.com and read up on 2 and 4-stroke engines.

It is a great resource for engines and the like.

If I have erred on any of my info here please correct me.

Lee W.

 

[Adrenaline]

Okay I understand now. Thanks LWilson!
I already know how the four stroke, two stroke and diesel engines work but thanks anyways!

 

[KXTodd]

http://www.maximumsled.com/mountain/garage/2strokeprinciples/two-stroke_animation.gif
This shows what Lwilson said, pretty cool seeing it!

 

[bluerider125]

thanx everybody you helped alot.;)

-Rob

 

[dell30rb]

basically, the exhaust port and intake port on a 2 stroke are open at the same time. Some of the fuel/air mixture goes out the exhaust port during intake. The pipe creates a pressure wave, that crams the gas back in the cylinder... more power and increased efficency

 

[LWilson250]

I've already said that dell. lol.

Lee W.

 

[bruce j]

I'm no expert in exhaust systems, but it seems to me 4-stroke megaphone exhausts do use some of the same principles as expansion chambers. The megaphone looks like it would work the same as the diffuser cone in the expansion chamber, helping pull the exhaust out of the cylinder. Of course these systems have no need of a baffle cone, like you guys have already said. From what I've heard of them, megaphones can give big power increases, but only within a narrow RPM range. Would love to hear some comments from people who design 4-zstroke exhaust systems on this.

bruce

 

[dklink2000]

So by putting an aftermarket pipe on a 2 stroke, it is like changing the cam profile on a 4 stroke? That is why there are "torque" pipes and "rev" pipes.

 

[Danman]

In my opion (don't know that for a fact, but it seams logical) the Rev pipe would not create as much presure in the combustion chaber on the gas before it is burned letting the piston move faster or Freer. The oposite would apply to the torque pipe causing more compression to push the piston down faster creating more torque.

 

[dell30rb]

oops, i didnt even read your post lee!

Oh well.

The reason pipes increase torque / rev is because they are enginerred to create a better sonic wave at different speeds