2-stroke pipe on a 4-stroke?

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bluerider125

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Feb 23, 2002

598

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• Apr 20, 2002

• #1

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

***** freak.

LIFETIME SPONSOR

May 5, 2000

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• Apr 21, 2002

• #2

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.

 

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Adrenaline

Mod Ban

Oct 26, 2001

245

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• Apr 21, 2002

• #3

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?

 

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LWilson250

Member

Jan 1, 2001

683

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• Apr 21, 2002

• #4

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?

Click to expand...

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.

 

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Adrenaline

Mod Ban

Oct 26, 2001

245

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• Apr 21, 2002

• #5

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

 

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KXTodd

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Nov 25, 2000

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• Apr 21, 2002

• #6

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

 

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bluerider125

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Feb 23, 2002

598

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• Apr 21, 2002

• Thread starter
• #7

thanx everybody you helped alot.;)

-Rob

 

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dell30rb

Uhhh...

Dec 2, 2001

1,510

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• Apr 21, 2002

• #8

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

 

L

LWilson250

Member

Jan 1, 2001

683

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• Apr 22, 2002

• #9

I've already said that dell. lol.

Lee W.

 

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bruce j

Member

Dec 14, 2001

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• Apr 23, 2002

• #10

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

Damn Yankees

Feb 18, 2002

764

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• Apr 23, 2002

• #11

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.

 

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Danman

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Nov 7, 2000

2,208

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• Apr 23, 2002

• #12

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.

 

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dell30rb

Uhhh...

Dec 2, 2001

1,510

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• Apr 23, 2002

• #13

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