pipe mods

[the glassman]

has any one tryed to modify there pipe.

can the tail pipe be enlarged pros/cons
would shortening or lengthening the head pipe change any thing.

i kinda understand how a pipe works but i was just curiose

[wilkin250r]

There are a few companies that offer custom pipes built from scratch, so modifications are obviously possible.

The tail end is called the "stinger". I have never done actual real-life modifications, but I have done "theoretical" modifications. All the aspects of the pipe have a mathmatical relationship to each other. According to those calculations, a larger stinger diameter will give you less power. A smaller stinger diameter will give you more power, but in real-life applications, it causes overheating.

The different sections work together, so it's not wise to just change one, like the header length. If you shorten the headpipe AND the expansion chamber, this would theoretically shift the power to higher rpms.

[C-LEIGH RACING]

The stinger is nothing more than a presure bleed off, all the workings of the pipe is from the face of the piston out to where the stinger welds on.
Changing the stinger size ID or the overall silencer & stinger lenght, large or small would have an effect on the jetting in the end.
Bigger ID stinger or shorter overall lenght would lean the jetting but takes a drastic change to make a noticably difference.
Neil

[the glassman]

so is there a way to spread the power band out over a longer range of rpms. The way i was figuring was that if the stinger id was larger then the back preasure would be alitttle lower thus alowing the motor to get into its powerband a little sooner.
probly completely wrong in my thinking but hey:)

[the glassman]

Originally posted by wilkin250r
There are a few companies that offer custom pipes built from scratch, so modifications are obviously possible.

The tail end is called the "stinger". I have never done actual real-life modifications, but I have done "theoretical" modifications. All the aspects of the pipe have a mathmatical relationship to each other. According to those calculations, a larger stinger diameter will give you less power. A smaller stinger diameter will give you more power, but in real-life applications, it causes overheating.

The different sections work together, so it's not wise to just change one, like the header length. If you shorten the headpipe AND the expansion chamber, this would theoretically shift the power to higher rpms.

so the longer the headpipe and the expansion chamber the more the power is in the lower end

[the glassman]

:cool:

[wilkin250r]

Originally posted by the glassman
so the longer the headpipe and the expansion chamber the more the power is in the lower end

Yes. If you read the Two Stroke Article (http://www.atvriders.com/articles/twostroke.html), you can see an animation about the pressure waves created in the expansion chamber.

Your powerband is determined by the strength and timing of those pressure waves. If the headpipe is long, the first wave takes longer to arrive. If the piston is traveling really fast (high RPM), the pressure wave arrives too late and doesn't do any good. The later the pressure wave, the slower the piston needs to be traveling for proper timing to achieve the most benefit. Low RPM boost.

A shorter headpipe will allow the pressure wave to return faster, which allows the piston to be traveling faster. High RPM boost.

There are TWO pressure waves that benefit power, we've only talked about the first. But to build the best power, the second wave needs to be timed to compliment the first wave. This is why you would modify both the headpipe AND the expansion chamber. If you had one long and one short, you wouldn't end up with a good compromise of high and low end, you would just end up with garbage and lousy performance on both ends.

[wilkin250r]

Originally posted by the glassman
so is there a way to spread the power band out over a longer range of rpms.

Yes. It's in the divergence and convergence angles.

The area where your pipe starts to get wider is called the divergence cone. If this is a narrow angle (gets wider slowly), it will spread out the first pressure wave, creating a more broad powerband. The trade-off is strength. The more you spread out that pressure wave, the less strength it has, and less power you'll get.

The same is true of the convergence section (where your pipe starts to get narrow). A narrow angle will give you a wider, but less powerful powerband.

[C-LEIGH RACING]

Wilkins,
You see in the animation where some of the fresh charge is still in the pipe after the piston has closed the port off. In slow motion I guess its reached a point where the rpm has gone higher than the pipe can support.
If I had a ink pen I could shorten that first cone & get it matched :D .
Neil