When the exhaust travels out the exhuast port, so does good gas......and when the engine revs high enough, a wave is sent back through the pipe shoving that clean gas back into the combustion chamber, giving the powerband, thus extra power...its a rough explaination, but thats pretty much it..i dunno if its different on a blaster...but generally for 2 strokes

Sean

 

Thats pretty much accurate right there. It is not 2 stroke specific either, it is just normally more noticable on a 2 stroke by design.

Funny how you "guys" pick some pretty colors for your power bands...pink, purple....bunch of faries...[img]i/expressions/face-icon-small-wink.gif[/img]

 

Next time your out driving with another 2-stroke, listin to the sound. You can hear when the power band kicks in and you'll really notice the motor start reving really fast and high( a good bike to hear it on is a YZ125/250).The powerband is why different pipes do different things.

The large chamber inside the pipe draws out the spent exhaust (along with some fresh gas). Then, when the exaust moves out the pipe it suddenly hits the small part where the scilencer attaches. Sence more gas is moving out the small end of the pipe that can fit through, some gets pushed back (like a sonic wave) towards the port. As this exhaust moves back it also keeps the new gas from going right out the exhaust port. During the 2 -stroke cycle, the exhaust and intake are both open for a short period of time. So without the wave of exhaust coming back, more gas would flow out the port.

Now, This is where it gets intresting. At different RPM's The engine is moving at a different speed..When the engine is going faster, so is the exhaust. Sence the exhaust port is only open for a short time it only gives that sonic wave a very small time to bounce back..So, when the engine is going to slow the waves aren't making it back in time to push that extra gas in. BUT, when the speed is right the exhaust is creating that back pressure that keeps gas from escaping out the exhaust port. This is called the powerband..After a certian RPM the engine will be going to fast and the exhaust wave will be returning too fast, thus not making it inside the port in time...

This is why all pipes are different. The size and length create a huge roll in determining the powerband..The longer the pipe chamber is, the more time it will take the wave to return, thus making the powerband at a higher RPM range..and vice versa.
Hope you can understand my jiberish. [img]i/expressions/face-icon-small-smile.gif[/img]

 

Huh? That was all very interesting and informative, however, i have absolutly no idea what you just said. I do however like the idea of that sonic boom thing. I think my powerband is blue since my Yamaha is completely stock. I want a red one to match the plastics though.