Wouldn't this be nice! A self-tuning pipe

[SUPERJET-113]

I dont know if this has been mentioned before, but it would be awesome to have something like this on our ski's! Would it be possible to make one for a PWC? Maybe some of you R/C head will know more about this contraption.
It aint to gawd damn buku! :Banane26: :doh::laugh2:

http://www.bukupower.com/
YouTube - BUKU POWER ACTIVE PIPE

 

[Frosty]

awesome!!

 

[Ericfox]

that is sweet!

 

[SUPERJET-113]

It probably wouldnt suprise me if the factory hardcore snowmobile teams have something like this, but I have no clue. They always seem to be on the cutting edge more so than PWC.

 

['Crockett]

I actually looked into this seriously a few years back because obviously the benefits for watercraft would be huge . . . .

It's a real tricky proposition because you want the pipe to be long for bottom end and then it needs to shorten as the R's go up for peak RPM, this goes exactly against what the pressure inside the pipe is trying to do.

You have to have a means to overcome the internal exhaust pressure and drive a movable cone back towards the headpipe for a length of about 1 1/2" to 2". Add in the factors of temperature,proper sealing and burned fuel/oil residue trying to gum everything up and it's nearly impossible to design something that would react quickly enough to be effective and function properly for an extended amount of time.

This is why we are fortunate that we run in water . . . . we can utilize H20 injection and "fool" the pipe into thinking it's getting longer and shorter. I'm sure that a varible length pipe is probably what Ross Liberty and the Factory pipe crew were working on when they realized that the same could be acheived by controlling the flow of water through the pipe and changing the speed of the exhaust pulse by manipulating air density.

H20 injection has it's issuses especially in Salt water and is far from reliable in general but it's probably as close as you're gonna come to an "self adjusting" pipe.

JMO

 

[the only couch rider]

would this be the exhaust version of the wetwolf AAT

 

[SUPERJET-113]

It appears to only lengthen the chamber in the lower rpm range at full throttle then the length shortens after the pressure diminishes.

I noticed that too and was wondering if maybe the sound track was off or something! lol But it looks like the video was made by the company, so I doubt they messed it up that much!

BTW - Great explanations, comments, and observations Crockett and #0! It really helps me understand and get thinking about the physics and mechanics of our ski's. Much appreciated! :beerchug:

This thing would be so bad azz! Malone pipe? What Malone pipe? Hey bro, whats a B pipe? :stooges:

 

[#ZERO]

That would end the debate of the limited or mod chamber for sure.

I find it interesting that they are using a compression spring to put pressure on the convergent cone to lengthen the main chamber body.

It appears to only lengthen the chamber in the lower rpm range at full throttle then the length shortens after the pressure diminishes.

It would be even cooler if that spring was adjustable like a flow control valve and turning the chamber body would adjust your torque band.

Looks like it would be relatively easy to make if I could just find someone that makes diffuser and convergent cones in the right sizes.

Then main chamber could be fabricated from aluminum or stainless pipe on a lathe with threads and high temperature o-rings for sealing into compression body.

 

[spence]

wow that things sweeeeet

 

['Crockett]

Keep in mind that the pipe shown is for an RC car (>Click link<) . . . . pressures are much lower and fuel is thinner <----- read as: Less gumming up of moving parts.

To build this on a larger scale would not be impossible, but if you had to tear it apart regularly to unfoul it and maintain correct movement and function of the parts then it really would only be practical for a pure race application where it could be tinkered with regularly between moto's.

Myself, I was looking at it as potentially something that could be used for rec riders as well as racers without having to be constantly monitored for proper function.

One possibility that I looked at was a rotary actuator that "screwed" a threaded chamber together and apart . . . but again,it had to many moving parts, reacted too slowly, had too much potential for fowling and the additional weight and electronics would make it impractical to deal with.

JMO

 

[MADMAT]

Wow. That is killer and I never saw it coming!! A friggin moving adjustable chamber!!!

Very interesting.

 

['Crockett]

I actually looked at many options but kept coming back to the issue of fowling of moving parts an maintaining a perfect seal as the two biggest problems to overcome.

I then began to look at it from the perspective of trying to change the internal volume of the chamber. Interestingly, as Couch Rider mentioned the WetWolf type of mechanism is one I looked at also, as introducing and object into the chamber would decrease volume by displacement of area. Potential solutions to this volume regulation scenario also included an expandable internal bladder, a colapsable liner and a de-formable sidepanel. I even briefly considered a dual outlet pipe with different length cones and a gate valve to deflect ehaust flow from one to the other.

Once Factory Pipe released their H20 injection and I treid my first unit it became apparent that it really was the simplest most effective way to do it and I no longer saw the point in researching it any further.

 

[#ZERO]

If you think about how many time this pipe is going to operate back and forth there probably wouldn't be a real issue with burned fuel/oil residue trying to gum everything.

The pipe could always be cleaned if it became a real problem.

I would just be worried out the compression body acting as a waterbox causing the convergent cone not to extend properly.

 

['Crockett]

I would just be worried out the compression body acting as a waterbox causing the convergent cone not to extend properly.

Actually, that's exactly what they are trying to do . . as pressure rises in the closed end of the pipe "cone housing" with help from the springs preload, it drives the cone back and raises peak RPM by bouncing the sound wave back quicker and maximizing efficient scavenging for the higher rpm.

Dispite what the video may seem to show, you want a long pipe at lower rpm's and a shorter one at high rpm's to create the broadest most powerful powerband.

 

[#ZERO]

I'm still trying to figure out if that convergent cone has a hole at the very end or if the hole in the side is the only exit. Also if the small cone at the end of the spring is just to hold the spring or is some type of parabolic exhaust deflector.

 

['Crockett]

There appears to be a "cup" in the end cap of the closed end that the stinger points into . . . . . When the throttle is first cracked the exhaust pressure fills the main chamber and drives the cone out towards the cup.

As the rpm's build, the pressure coming out of the stinger into the "cup" begins to act like a jet engine and the "thrust" drives the cone forward aided by the pressure building in that section and the force of the spring.

At least that's how it appears to me to be working. . . . .


BTW . . . I wasn't questioning your level of understanding of how a pipe works, I just mis understood your wording in your post. . . . . I also wanted to state how it functions clearly for others who are not aware . . . . .

 

[#ZERO]

After visiting the web site they have some better exploded views of the internals and it appears like they aren't lengthening the pipe but just controlling the back pressure with another secondary expansion chamber. There's also a hole in the diffuser cone to push the internals forward while the pipe remains the same length.

It seems like it would have been more effective to lengthen the main chamber body by putting pressure on the convergent cone thus creating a longer pipe without the use of that secondary chamber to control the back pressure.

http://www.bukupower.com/howitworks.html

Here are some diagrams and terms if needed explaining the effects of a pipe.

 

['Crockett]

I haven't had a chance to look at all that yet but I will . . . . . .

I'd say this though in regards to their design, they have such a small amount of work to do (weight of vehicle vs resistance) in comparison to what it takes to move a watercraft with all the drag that needs to be overcome just to get it moving. They may be able to live with a real compromise in design effeciency simply because they don't need the broad powerband we would require.

 

['Crockett]

O.k. . . . after looking at the working model it appears that the inner pipe is like a shuttle valve that moves back and forth effectively lengthening and shortening the head pipe to vary chamber volume. I'm also thinking that there may be nothing more happening than simply an equalization of pressure on both sides of the cone after the initial shift to the "long" position thus allowing the spring to do the actual work of pushing the inner chamber back to the "short" position.

We used to mill down the head pipe mounting flange on a Coffman's 440/550 pipes it shortened the overall length of the headpipe section with out affecting chamber volume (bottom end) as much as shortening it in the center did. You got a few more rpm's without sacrificing so much bottom end. This seems to be what they are getting at with this set up.



This little pipe is a very cool exercise in varible exhaust but it really may be more gimmick than anything else when it comes to how much difference it makes to the actual performance of these little RC cars.

Their product is very nice and very well presented . . . . I'm sure they will sell a bunch of them regardless of how well they work in the end !


Good stuff . . . . I love things like this . . . . . . .

 

[#ZERO]

That's exactly what I'm thinking that this is just another gimmick to sell RC guys an expensive pipe.

If you look in the video at the distance between the engine and where actual chamber starts, that small amount of movement in the header section wouldn't make that much of a change in the total pipe length.

This is more of a variable back pressure system then a variable chamber.