Its a good book to start with if you want to understand how a two stroke engine including exhaust works. A complete twostroke pipe has properly tuned header, convergent, belly, divergent and stinger sectionsa difficult process. Then after you read it about two dozen times, some of the expansion chamber theory will start to sink in, and youll know that the first thing that you need to do is pick an rpm that you want it to peak at. Faster computers and better aiming of the fuel was played with. Its very complex, and if you want to know more i can recommend you to start with reading a. The arrangement of the intake and exhaust ports in a two cycle engine affords a unique opportunity to use the exhaust system to influence the intake sequence. The expansion chamber construction utilities have been extended considerably and are now accessed under a separate item on the main mota menu. It makes use of the energy left in the burnt exhaust exiting the cylinder to aid the filling of the cylinder for the next cycle. Twostroke engines operate in two strokes, instead of four, and this animation illustrates the twostroke engine operation in conjunction with its expansion chamber showing the reflected pressure wave on the fuel charge. Twostroke petrol engines are preferred when mechanical simplicity, light weight, and high powertoweight ratio are design priorities. As the forces in a twostroke pipe design have become more wellunderstood, designers have been able to create engines that take more advantage of them and in fact require an expansion chamber to run at all. They often recover charged air which is passing into the exhaust, along with increasing cylinder pressure.
This will get you started by providing, for your engine, the dimensions of an expansion chamber with a 2stage or 3stage diffuser. To build an expansion chamber, first you have to get a copy of gordon jennings 2stroke tuners guide. Unlocking the secrets of 2 stroke expansion chamber exhausts e1. The pressure inflates the flat sheet into its final rounded shape. The way to calculate the return timing and length of the negative wave in a 2 stroke expansion chamber is by this formula. The stock pipe is basically a straight pipe anyway but i want to pit a straight pipe on it with a new school silencer on it. This small java applet uses design rules according to, and, to size a tuned pipe for a 2 stroke piston engine. While moving downwards after ignition, the piston exposes the exhaust opening, and the burned gas streams into the exhaust pipe like a high pressure shock wave. The 2 stroke engine animation demonstration has an added device commonly known as an expansion chamber attached to the exhaust port. But im curious as to how an expansion chamber would affect a four stroke engine.
But at what part of the powerband it does it is dependent on how far from the engine the diffuser cone and baffle cone are. Fourstroke expansion chambers general dirt bike discussion. Twostroke engines do not use fuel efficiently, so you would get fewer miles per gallon. Why do twostroke engine exhaust pipes look so strange. This coefficient kh is called the horn coefficient, with typical values between one and two. How to design a two stroke expansion chamber performance exhaust step 2 aumechanic.
Direct comparison between different types of exhausts for the twostroke engine, on the left you can see the engine and its exhaust, in the. One other old way of calculating the dimensions of an expansion chamber relied on generic formulas that put the emphasis on the wrong things. Performance fabrications is dedicated to manufacturing the finest bespoke hand crafted exhaust systems available. I bought a new two stroke piston engine on special for the purpose of showing how to measure up exhaust port area and timing to plug in to the 2 stroke expansion chamber exhaust software. Two stroke engine and exhaust design software post by gerrit sun jan 17, 2016 10. A submenu offers the two selections constructing the development pattern of a cone and printing the development pattern of a cone. Engineering acousticssonic supercharging of 2 stroke engines. What happened was the 4 stroke sounded pretty annoying and i like the sound of a 2 stroke with a pipe, but it doesnt work the same on a 4 stroke. Jan 15, 2005 ok, i had a question up a week or two ago about why two strokes have their expansion chambers in the pipes. Page 1 of 3 asymmetric timing in the twostroke engines posted in the technical forum. For instance pipe calculators would determine the belly diameter based on blairs maximum size 2. An expansion chamber is an exhaust system used on a twostroke cycle engine to. Freeware 2 stroke expansion chamber exhaust calculator program.
You can also save and load the data by using the provided functions. An expansion chamber is an exhaust system used on a two stroke cycle engine to enhance its poweroutput by improving its volumetric efficiency. The expansion chamber an improperly named device utilizes sonic energy contained in the initial sharp pulse of exhaust gas exiting the cylinder to supercharge the cylinder with fresh mixture. I put an expansion chamber 2 stroke pipe on a 4 stroke once just to see what happened.
This software covers the 3 stage diffuser type expansion chamber exhaust as per equations provided in his book entitled design and simulation of two stroke engines published in 1996. There is this nice animation of a 2stroke engine with an expansion chamber. Two stroke engine and exhaust design software north. Bigger carburetors, higher compression ratios, altered port timings and expansion. Another simple 2 stroke expansion chamber design program scroll down to. Two stroke engine expansion chamber design software keywords.
For a 4 stroke engine, the problem of loosing charge air to the exhaust is entirely neglectable. Nov 02, 2019 the operation of a two stroke engine equipped with a properly tuned pipe is shown in the animation below, for a step by step description of the process, please follow the link below the animation. Making an expansion chamber is a very time consuming and requires ver high levels of works. Two stroke design instead you can enter the data of your cylinder with extreme facility and precision, and then analyze the port areas and the timing area in the engine cycle timing for each phase. Time is required to pass from the opening of the exhaust port till the opening of the transfer port translated into. New version of 2t exhaust calculator it is a freeware 2 stroke expansion chamber exhaust calculator program download at. Npp neils power pipes handcrafted custom pipes and. Apr 06, 2012 expansion chamber building, two stroke tuning,pipes karl plant. The expansion chamber is the most tunable component on the modern two cycle engine and dramatic gains in power can be achieved with the correct design. As the forces in a two stroke pipe design have become more wellunderstood, designers have been able to create engines that take more advantage of them and in fact require an expansion chamber to run at all. A complete two stroke pipe has properly tuned header, convergent, belly, divergent and stinger sectionsa difficult process. The operation of a twostroke engine equipped with a properly tuned pipe is shown in the animation below, for a step by step description of the process, please follow the link below the animation. For more info on racingsm software check out our website.
I have plans this winter to put my yz 125 motor in it but i would like to see how this little motor runs with a good pipe vs the stock one that i. Graham bell, two stroke performance tuning, isbn 0854293299. Expansion chamber for 2 stroke what do u recommend. What will a two stroke run like without an expansion chamber. This is a module for 2stroke exhaust calculation based on famous g. Why dont 4stroke motorcycles have expansion chambers. Its a good book to start with if you want to understand how a twostroke engine including exhaust works. The worlds leading 2stroke engine simulation software for 3. If any of you have any ideas on this please share them, thanks. On a twostroke engine, an expansion chamber or tuned pipe is a tuned exhaust system used to enhance its power output by improving its volumetric efficiency. You can compare this animation to the animations in the car engine and diesel engine articles to see the differences. Exhaust pipe design with cone layout software by paul crowe if you have ever tried to layout a conic section on sheet metal, cutting just the right piece, that when rolled over and joined on edge, you have a cone with the exact shape, size and angled openings desired, you know its not easy. The calculations are assuming a speed of sound in the exhaust gas, which is not known exactly.
There are exhaust manufacturers now that are mating up tuned pipes to tuned ported engines to get the best possible supercharging effect at given. On a two stroke engine, an expansion chamber or tuned pipe is a tuned exhaust system used to enhance its power output by improving its volumetric efficiency. How twostroke expansion chambers work, and why you should. How to design a two stroke expansion chamber performance exhaust. However, the two stroke cycle can be difficult for some to visualize at first because certain phases of the cycle occur simultaneously, causing it to be hard to tell when. That is because the pressure wave created when the exhaust suddenly enters the exhaust pipe travels at a certain speed, so many meters per second. Fabbing up a complete 2 stroke pipe vintage dirt bikes. The software uses mathematical formulas that are approximations of reality, and the software made for homecomputers uses even more simplified formulas because good simulation of expansion chambers requires much more computerpower than you homepc can offer. I have plans this winter to put my yz 125 motor in it but i would like to see how this little motor runs with a good pipe vs the stock one that i think is holding it back. Twostroke oil is expensive, and you need about 4 ounces of it per gallon of gas. I didnt really like many of the pipes but a few were ok but i wanted more. Hence, more people are now looking at restoring and tuning these bikes. Small values of kh are best suited to grand prix engines with narrow power bands, larger.
With symmetric timing, the transfer port opens after the exhaust port and closes before the exhaust port. There is this nice animation of a 2 stroke engine with an expansion chamber. As the 2 stroke engine animation below shows, a twostroke engine in its purest form is extremely simple in construction and operation, as it only has three primary moving parts the piston, connecting rod, and crankshaft. Two stroke engines operate in two strokes, instead of four, and this animation illustrates the two stroke engine operation in conjunction with its expansion chamber showing the reflected pressure wave on the fuel charge. A simple 3 stage two stroke exhaust calculator based on formulas of g. This stroke occurs immediately after the detonation of the charge. Walter kaaden, the chief engineer for mz motorcycles in the 1950s, is generally considered the father of the modern two stroke expansion chamber. Two flat representations of the required finished pipe are cut out of sheet metal.
Two stroke tuners handbook 2 another mistake commonly made, sometimes even by those who have enjoyed some success in modifying twostroke engines, is to believe in a kind of mechanistic magic. Resonanzauspuff expansion chamber animation duration. It is the twostroke equivalent of the tuned pipes or headers used on. How an expansion chamber works a nice animation another good. We now have a simple 2 stroke expansion chamber design program. Expansion chambers in pistonvalveless two stroke engines are useful for a variety of reasons. This will get you started by providing, for your engine, the dimensions of an expansion chamber with a 2 stage or 3stage diffuser.
Then after you read it about two dozen times, some of the expansion chamber theory will start to sink in, and youll know that the first thing that you need to. Ok, i had a question up a week or two ago about why two strokes have their expansion chambers in the pipes. Using the expansion chamber to basically supercharge the combustion chamber with sonic waves was still going to be the norm, for now. You would burn about a gallon of oil every 1,000 miles if you used a twostroke engine in a car. Two stroke engine expansion chamber design software author. The edges of the two identical flat cutouts are welded together forming a sandwich. This was on a 49cc 4 stroke pitbike engine, not a scooter.
Software for fine tuning and design of two stroke engine by. An expansion chamber is an exhaust system used on a twostroke cycle engine to enhance its poweroutput by improving its volumetric efficiency. Racingsm software has features for many different areas 2 stroke exhausts development, drag racing features, simulators, carburetor tuning, connectingrod analysis etc with all this knowhow along with lufo racing heritage, we believe this is a very fair price. Wrt1d1x2sw where wrt1 is the wave return time for the first part of the wave, d1 is the distance from cylinder port to beginning of diffuser, and sw is the speed of the wave which is determined by the temperature and. To build an expansion chamber, first you have to get a copy of gordon jennings 2 stroke tuners guide. With the traditional lubrication technique of mixing oil into the fuel, they also have the advantage of working in any orientation, as there is no oil reservoir dependent on gravity. Could it give a four stroke the two stroke famous bighit. Jul 25, 2007 exhaust pipe design with cone layout software by paul crowe if you have ever tried to layout a conic section on sheet metal, cutting just the right piece, that when rolled over and joined on edge, you have a cone with the exact shape, size and angled openings desired, you know its not easy. Freedownload here this program is not a part of mota, but it has been put together by the same engineers as a starting point for those wishing to begin from scratch. Moreover you can have advices for the development of the engine thanks to the help of tested formulas for intake, exhaust, blowdown and transfer.
Typical gokart engine expansion chamber with integrated muffler. Asymmetric timing in the twostroke engines the technical. We also have a simple 2 stroke expansion chamber design program. The basic theories of twostroke tuning were not seeming to change based on what method the fuel was delivered. I have a few different 450 silencers, ill probably use one of those. Im building a little street legal 30s style hillclimber out of a 73 dt1250.
Two stroke engine and exhaust design software post by gerrit. The exhaust would not go all the way through the pipe in 1 cycle. This program calculates the dimensions for both double and triple stage diffuser expansion chambers from a few basic engine dimensions. How twostroke expansion chambers work, and why you should care. He reportedly said youll know when you have the design right, because the chamber will then be impossible to fit on the motorcycle without having it drag the ground, burn the riders leg, or. Two stroke engine expansion chamber design software. It is the 250cc to 500cc sized bikes that have seen a marked increase in second hand values. The arrangement of the intake and exhaust ports in a two cycle engine affords a unique opportunity to use. Dans motorcycle two stroke motorcycle exhaust pipes. The following animation shows a twostroke engine in action. On one end of the pipe a fitting is welded and highpressure water is pumped into the cavity between the sheets. That is because the pressure wave created when the exhaust suddenly enters the exhaust pipe travels at a. How to design a two stroke expansion chamber performance.
I have been into 2 stroke bikes for over 28yrs and i have bought and tested many exhaust pipes on all the bikes i have owned to find the best one for my needs. We also have a simple 2stroke expansion chamber design program. Mota 2 stroke engine software, user manual ian williams tuning. The biggest difference to notice when comparing figures is that the sparkplug fires once every revolution in a twostroke engine. However, in the case of animated waves, you have to stop the animation by clicking the wave stop button before the two. On a twostroke engine, an expansion chamber or tuned pipe is a tuned exhaust system used. How to plot two stroke expansion chamber cones on paper from software duration. Direct comparison between different types of exhausts for the two stroke engine, on the left you can see the engine and its exhaust, in the. Any donations greatly appreciated, please use paypal link. Very simplified explained, a good expansion chamber works like this. Racingsm software has features for many different areas 2stroke exhausts development, drag racing features, simulators, carburetor tuning, connectingrod analysis etc with all this knowhow along with lufo racing heritage, we believe this is a very fair price.
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