Exhaust Tune question

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firewalker

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Ok just got my new Rampage running last night after a ton of carb adjustments (it was way rich from the factory). The question I have is...I want to switch to the X-Can exhaust and/or do some tweaking to the stock exhaust, but I wanted to ask all here if the length of the pipe from the muffler to the output makes a difference in tuning..I know that with many engines this can drastically change things. Please post your opinions at your earliest convenience I will not be making changes for a little while.
 
Im no pipe builder but header length plays an important role in engine performance. Especially in these little 2 strokes. I just wish I knew exactly what it did :D
 
ya don't mix apples and oranges! (back pressure is the magic)


one pipe to another is always going to need carb adjustments...


it's all about the back pressure and length...


if it is timed just right (length and size)


that back pressure can help the tolerances of the internal parts of the engine work easier...


causing cleaner higher RPM's,torque and mas clean burning... :)


the rest of the pipe that is not needed is used for looks or mega nice rumble...
 
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if you want a good pipe you start with tube size the same as your exhaust port then gradually step up to bigger sizes the farther you get away from the engine into your expansion chamber that gives you low mid and topend when you start out small that gives your back pressure and as you take the tubing bigger is where you start the climb for your topend but make sure your exit stinger is around a half inch diameter. hope that helps explain a little.
 
The resonating back wave from the convergence cone is what is really supercharging your engine. Header length plays part of the role of how that wave is timed with the engine. Basically, it changes the RPM range of the pipe.


If you take a look at some examples of tuned pipe theory you can see that the formulas for designing pipes have variables for header diameter and length, divergent cone angle and length, belley diameter and length, convergence cone angle and length, and stinger diameter and length. Basically, what I'm saying is that you can change the header length and yes it will change the tuning of the pipe, however, if the pipe isn't designed for it, you can actually lose alot of performance. Examples of pipes that shouldn't be touched are the short compact pipes for the HPI Baja such as the Jetpro track pipe and GBE Hornet pipe. They've setup the divergent and convergence cone in a way to work with such a short header. Extending a header on a pipe like those to a somewhat standard 8-9" range like you see on full size pipes would actually throw those pipes so far out of tune that you might as well run a stock can.
 
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