To learn more about how expansion chamber exhaust systems work, read this great primer: How two-stroke expansion chambers work and why you should care. Graham Bell. A slightly better scanned version of the Jennings Handbook may be found here. Another link to Graham Bell's book. Low Carbon steel, stainless steel, or Titanium are common materials for fabricating expansion chambers. Sheet metal around the thickness of 16 gauge.
Flat sheet metal is rolled into cones and round sections, which are then welded together section by section. Although time consuming, it is usually the method chosen for development of a new design due to its flexibility, accuracy and low tooling costs. Use this calculator to make templates for the cones. Two flat representations of the required finished pipe are cut out of sheet metal.
The edges of the two identical flat cutouts are welded together forming a sandwich. On one end of the pipe a fitting is welded and high-pressure water is pumped into the cavity between the sheets. The pressure inflates the flat sheet into its final rounded shape. This method can be quicker than hand forming and only slightly more costly in tooling, however it requires a number of trials before a finished design as accurate as hand formed or stamped can be produced.
All curves must be made in a single plane so cutting apart and re-welding is often required but the final product can be as good as a stamped pipe if enough care is taken to be precise. Flat sheet metal is pressed between a male and female mold in the shape of the required pipe.
Each half of the pipe is stamped this way and the two halves are welded together. Stamping requires expensive tooling and machinery and is used only for mass production. Moped Wiki. Personal tools.
Really interesting way to build an expansion chamber. Crazy, All I need is a hydraulic pump that pushes psi.Building The Ultimate Two Stroke Engine!
I think someone posted something about that a while back. Really cool stuff though. Ive hand rolled one before and it sucks, and the hydro formed stuff looks sooo much better. I've been on that site for a few years.
Good people too! Rebuilt my bike from that site. Beautiful bike man I have wanted an rd, rzsuzuki gammah1, h2, h3 or the like for soo long. I've never come across a deal at the right time. How does it run?
Runs excellent! Been working on different pipe styles for power ranges and these pipes rock, get lots of midrange and top end. Similar pipes with the larger mids produce alot of top, only good for WOT.
Stockers give a good low end to midrange and no top end. Have some old Bassani's going on this summer. Excellent job on those pressure formed pipes. Guys, Here's another good article to reference when hydroforming expansion chambers.Simply put, it's because the two-stroke exhaust system, commonly referred to as an 'expansion chamber' uses pressure waves emanating from the combustion chamber to effectively supercharge your cylinder.
Kaaden understood that there was power in the sound waves coming from the exhaust system, and opened up a whole new field in two-stroke theory and tuning. An engine's exhaust port can be thought of as a sound generator.
Each time the piston uncovers the exhaust port which is cut into the side of the cylinder in two-strokesthe pulse of exhaust gases rushing out the port creates a positive pressure wave which radiates from the exhaust port.
The sound will be be the same frequency as the engine is turning, that is, an engine turning at rpms generates an exhaust sound at rpms or cycles a second--hence, an expansion chamber's total length is decided by the rpm the engine will reach, not displacement.
Indeed, the only advantage to this crude pipe system was that it was easy to tune: You simply started with a long pipe and started cutting it off until the motor ran best at the engine speed you wanted. Of course those waves don't radiate in all directions since there's a pipe attached to the port. Early two strokes had straight pipes, a simple length of tube attached to the exhaust port. This created a single "negative" wave that helped suck spent exhaust gases out of the cylinder.
And since sound waves that start at the end of the pipe travel to the other end at the speed of sound, there was only a small rpm range where the negative wave's return would reach the exhaust port at a useful time: At too low of an rpm, the wave would return too soon, bouncing back out the port.
And at too high of an rpm, the piston would have traveled up the cylinder far enough to close the exhaust port, again doing no good. So after analyzing this cut-off straight-pipe exhaust system, tuners realized two things: First, that pressure waves could be created to help pull spent gasses out of the cylinder, and second, that the speed of these waves is more or less constant, though it's affected slightly by the temperature of the air.
Understanding Muffler Design and Sound Absorption Strategies
Higher temperatures mean that the air molecules have more energy and move faster, so sound waves move faster when the air is warmer. A complicating factor here is that changes in the shape of the tube cause reflections, or changes, in the sound waves: Where the section of the tube grows in diameter, there will be sound waves reflected back towards the start of the tube.
These waves will be the opposite of the original waves that they reflected from, so they will also be negative pressure waves. The next important discovery was made--by gradually increasing the diameter of the tube, a gradual, more useful negative wave could be generated to help scavenge, or pull spent gasses out of, the cylinder.
Putting a divergent cone on the end of a straight pipe lengthens the returning wave, broadening the power band and creating a rudimentary expansion chamber. So, to sum up, when the negative wave reaches the exhaust port at the correct time, it will pull some of the exhaust gases out the cylinder, helping the engine to scavenge its spent exhaust gas. And putting a divergent cone at the end of the straight parallel "head" pipe broadens the returning wave.
The returning negative wave isn't as strong, but it is longer, so it is more likely to find the exhaust port open and be able to pull out the exhaust gases. As with plain, straight pipes, the total length of the pipe with a divergent cone welded on determines the timing of the return pulses and therefore the engine speed at which they are effective.
The divergent cone's critical dimensions are where it starts the distance from the exhaust port to the start of the divergent cone is called the "head" pipewhile the length of the megaphone and the rate at which it diverges from the straight pipe determine the intensity and length of the returning wave--A short pipe which diverges at a sharp angle from the head pipe gives a stronger, more straight-pipe-like pulse. Conversely, a long, gradual divergent cone creates a smaller pulse of longer duration.
In addition, the negative wave is also strong enough to help pull fresh mixture up through the transfer ports. And while adding a divergent cone to the head pipe produced great tuning advantages, it had its limitations, too: The broader negative wave from a megaphone can still arrive too early and pull fresh mixture out of the cylinder. That's exactly the problem that Walter Kaaden had with the factory MZs.
How quiet can you make a 2 stroke?
He realized that putting another cone, reversed to be convergent, on the end of the first divergent pipe would reflect positive waves back up the pipe. These positive waves would follow the negative waves back to the exhaust port, and if properly timed would stuff the fresh mixture that was pulled into the pipe back into the exhaust port right as the piston closed the port.
In addition to head pipe length, divergent and convergent cone lengths, an expansion chamber has three more crucial dimensions. The length of the straight 'belly' between the divergent and the convergent cones, the length of the tailpiece 'stinger', or muffler, and the diameter of the belly section.
The stinger acts as a pressure bleed, allowing pressure to escape from the pipe. Back pressure in the pipe, caused by a smaller-diameter or longer stinger section, helps the wave action of the pipe, and can increase the engine's performance. This, presumably, happens since the greater pressure creates a more dense, uniform medium for the waves to act on--waves travel better through dense, consistent mediums.Understanding the different types of internal configuration will help you pick the right muffler for your application.
In this article we are tackling the age old question of how much of high performance muffler design is based on science and how much is slick advertising? With all the different styles and types of performance mufflers on the market with different sound attenuation strategies, it can get confusing to know what is best for your application. Starting from the top we should define what the purpose of a performance muffler is. Performance mufflers have three simple goals for perfect operation. First to absorb and dissipate.
Second to move exhaust gasses, and finally to maintain power and performance of the engine while achieving the first two goals. That then reflects the sound wave back upon the next sound wave entering the mechanism all without interrupting the exhaust flow. Each muffler is designed and tuned specifically for the vehicle it is intended for taking into account everything from cabin volume, to exhaust length, to desired level of exterior volume.
Clearly, designing and engineering mufflers that efficaciously contain, absorb and dissipate noise pulses and maintain power with cost efficiency at the same time is no easy task. Nor is it a one size fits all formula. Honestly, the most impressive thing that others identify in an automobile right away is the sound that your car makes. Performance mufflers actually improve the efficiency of the exhaust system and retain most of the power that your engine creates.
Some stock mufflers have been documented to rob 30 or 40 horsepower from a factory high performance V8 by creating excessive backpressure. Adding a performance muffler to your car can also help to reduce wear on engine components, by reducing engine heat and boosting exhaust flow.
Sound is simply a vibration that spreads as a wave through air. In an internal combustion engine, these pulses are created when the exhaust valve opens and the hot gas from the combustion chamber enters the exhaust system.
The exhaust gas exits the combustion chamber under pressure and meets the low pressure gas in the exhaust pipes and stack up on each other. However, the sound waves migrate through the media without any resistance, making their way down the pipe faster than the actual gases do.
If a crest of a pulse wave meets a crest of another pulse wave of the same frequency at the same point, the displacement is the sum of the two waves. In an eight cylinder engine, you can have eight pulse waves at the same frequency at the same point creating a lot of sound.
When these pulses reach your eardrum, the eardrum vibrates back and forth which causes the brain to recognize the motion as sound.
It is possible to add multiple sound waves together and get less sound by lowering the pressure pulses. This is where muffler design comes into play.How to make an upswept expansion chamber from your exhaust pipe and a second standard pipe from pistonbikes. The program I used for most of the distances and diameters was the 2 Stroke Wizard Pro version 3.
The first cone is longer in this design but that is to eliminate the need to make a long B section that gently gets wider the farther back it gets. The idea here is to be able to fairly easily make an expansion chamber with a peak rpm ofhorsepower between 7 and 8, and have a wide powerband unlike the peaky powerband of a racer. Below shows the pipe dimensions given by the 2 Stroke Wizard that you can use if you want it to be just right. The bottom pipe is what I am proposing as an easy to make alternative.
How does this DIY pipe compare to pipes available for purchase for this engine? The main two characteristics of an expansion chamber are the length from the piston to the midway point of the final cone, and the angle of the final cone. The longer it is due to a small anglethe wider the powerband. This DIY pipe has a small final cone angle which gives it a broader powerband, especially necessary for a one speed bike.
And the length should be made by you to perfectly fit the peak rpm's of the engine. If you do that then this pipe is better than anything offered. Look at how the final cone angle is greater on other available pipes than this one. That means they have a short powerband for racing with mutiple gears. And they are made to be closer to the engine which means they will offer a high rpm powerband which is not what you want with these engines. Click here to read how to exactly determine the powerband of an expansion chamber.
DIY Expansion Chamber How to make an upswept expansion chamber from your exhaust pipe and a second standard pipe from pistonbikes. After drawing this pattern on poster board add the curves according to their middle height. Cut out the final pattern, cutting along the curved lines and the two sides. Then use a Marks-A-Lot to transfer the pattern to the sheet metal, then cut it out. Bend the outer sides of the sheet metal to have a curve, then pull the side ends together, then clamp them in place, then weld the side ends together.
Then weld the cones to the middle cylinder, etc. After reading the performance book by Graham Bell I calculated this new pipes peak power rpm as But a standard 48cc Grubee engine has a peak rpm of In order to make the pipe match that rpm this pipe would have to have a longer belly length of 21cm.
For a free on-line pipe dimension calculator that gives similar results as the 2 Stroke Wizard click here.Home Contact Us About Us. At Cone Engineering we specialize in motorcycle exhaust componentsnot finished exhaust systems for a particular year or brand.
The following pages feature a selection of our most popular exhaust components generally used in motorcycle applications, cone exhaust stuff will provide you with the right specification. There you will find a complete listing of all our exhaust components. Our purpose is to be a source for fabricators, providing products that help them create something unique and different.
What everyone has in common is the need for high-quality components to make their task easier! And our components know no boundaries!
They serve every portion of the market, from the resurrection of bikes years old to current era road racers; vintage moto to dirt tracker; a stripped down rat-bike bought at impound to high-buck full-custom one-of-a-kind builds — beauty is in the eye of the builder! But you name it; our components fill the bill! What do you do? Well after you are done crying, man up. Then order some mandrel bends in stainless steel or mild steel and build your own brand new header!
And the best part is you can usually design your new header even better than the factory original! Maybe you could even build that ultra rare Twingle Scrambler exhaust that you once saw! From over different collector dimensions, configurations and materials in stock we have narrowed down the options a little to those most commonly used in motorcycle designs. For more choices try the main collectors tab from the home page.
We now offer several choices of pre-fabricated slip-on mufflers in both traditional and more modern styles. Instead of running a bare header try one of these megas to give a finished look and better sound to your bike. How about a few final choices? And last but not least, is a flat out mild steel max diameter race muffler.
A unique twist is the conical interior that lets you choose to run it either as a megaphone that increases from a 2. And most importantly, every muffler we make is based on our over 40 years of experience in building products for the motorcycle aftermarket exhaust industry! With over bare cones in stock to choose from, and hundreds of internal muffler component internals you have to be able to find something to stimulate you!
And remember that our components are very flexible, you can often manipulate our basic parts to give many more options - cones cut in half become heat shields, the same with collectors, louver cores can become exhaust tips - the only limit is your imagination! Exhaust Accessories. Along with the main components you may also need clamps, spring tabs, mounting tabs, heat shield tabs or other items.
You can also find these listed on the link below.Forums New posts Search forums. Media New media New comments Search media. Resources Latest reviews Search resources.
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How Two-Stroke Expansion Chambers Work, and Why You Should Care.
Last edited: Sep 30, Anybody tried anything along those lines? Arty Active Member. Joined Feb 12, Messages It's so ugly I love it! Arty said:. Joined Aug 4, Messages Neptunati New Member. Joined Jul 9, Messages Nate said:.
Steve Best Well-Known Member. Joined Sep 22, Messages 1, Last edited: Oct 22, Timbone Well-Known Member. Joined Apr 20, Messages 1, View attachment View attachment Clearly, the right way to do exhaust modding involves learning to weld. Any thoughts, tips or experiences you'd wanna share on this? Carl Walichnowski Active Member. Joined Jul 2, Messages Wow I just seen this monstrosity, it has to be a love hate relationship.