Tuned pipe theroy.

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The last article is kinda making to much hassle of an expansion chamber.
While most if the information in there is true, its not really something anyone should fiddle around with. It is basicly saying that if you don't tune your pipe to match your enginge you will most likely see a performance loss, wich most of us using a tuned pipe know is far from true.

Aslong as you hit the rpm range the pipe is made for you will get the performance increase.
Might be a problem if you use a pipe tuned for 30k rpm and your engine only does 20k rpm, then it wont do you much good since your engine will never hit the frequency the pipe is made to affect.
And tuning the pipe like the article implies would mean you would need a tuned pipe for every temperature and humidity levels etc. Thats just crazy, the pipes temperature does change the power peak sure, but like i said, aslong as your engine hits that rpm range you are fine.

The only time the advice in that article will be any good is if you have an engine running at a specific RPM all the time where you would like to have the maximum amount of power, wich might be the case with airplanes, don't know since I never flew one.
 
The second link was for nitro motors, I posted it to show the tuned pipe theory and how changing header length can affect motor performance. It was in no way implied that one should start hacking away at their pipe.

I have seen about 100 times posted on this forum about how "2 Strokes need backpressure to run properly" I was showing how a pipe doesn't use backpressure to push air and fuel back into the head that would otherwise have escaped, a tuned pipe uses a sonic (or sound wave) pulse to push air and fuel back into the head.
 
Oh i see, well i wasnt riding you for it. Just wanted to point that out. But so you know, soundwaves are changes in the airpressure wich in turn our inner ear and its parts register as sound.
So two-stroke engines do benefit from backpressure, calling it sonic waves is just another term for the same thing. Just like the blast wave from an explosion, its more appropriate since thats what happends inside the engine. And part of that blast wave is reflected back into the cylinder to generate the backpressure.

I find this wikipedia entry to be more exact about it.
http://en.wikipedia.org/wiki/Expansion_chamber

Cheers!
 
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While you are correct, most people don't understand the term "Backpressure" in the context that you are using. Most consider backpressure to be an obstruction or some device that causes a reduction in flow as to aid in low rpm torque. Something that "backs up" or restricts the pressure or exhaust gasses in the pipe. Which isn't the case in a 2 stroke. Small tube headers and a small diameter pipe helps low end torque in a 4 stroke application, but that has nothing to do with this conversation.

The pressure that is created within the pipe is a wave sending unburnt air and fuel back into the combustion chamber, not a restriction causing air and fuel to be essentially trapped in the cyl. If that makes sence. I am not explaining this to you Sir, I am clarifying to others that may happen upon this post. I am not disagreeing with you, in fact quite the contrary, I am trying to find another term or word that is a better match for the function of a "Tuned" pipe.

I just think "back pressure" is poor terminology for this application, it's too easily confused with a lack of flow, or as I stated, obstruction.

I will check out your link. Thanks.

Trip..
 
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