The Tuned Pipe Designer
This small Java applet uses design rules according to , , and , to size a tuned pipe for a 2 stroke piston engine. The calculations are assuming a speed of sound in the exhaust gas, which is not known exactly; also, it depends on the temperature and thus on fuel/air mixture and external conditions. In this applet, the gas conditions for methyl alcohol (methanol) and gasoline have been implemented. The results of the calculations can be used as a good starting point for experiments and fine tuning, deviations of +/-10% are surely possible.
Determining the Timing
|The animation shows, how to measure the timing angles of exhaust and transfer port.
These angles define how long the ports are open, expressed in crankshaft angle. You can
attach a disk with divisions in degrees to the crankcase and a pointer to the crankshaft
(or vice versa).
Then you adjust disk and pointer so that the it indicates 180° when the piston is at its bottom dead center. Now you turn the crankshaft until the port of interest closes (when the piston crown arrives at the upper edge of the port). It is helpful to point a flashlight or a halogen lamp through the plug hole or to remove the cylinder head.
Reading the angles in both directions must be symmetrical to the bottom dead center, e.g. a port opening at at 100° must be closing again at 360°-100° = 260°, as shown in the animation. The port timing angle (shown in blue) is then 260° - 100° = 160°. This means, that port is open while the the crankshaft turns 160°.
Usually the transfer port will have a shorter timing than the exhaust port.
Used Formulas (a mixture from , , and ):
The opening angles of the cones should be 4° to 10° for the opening cone and approximately twice this value for the closing cone.
Cut view of a tuned pipe with silencer.
Enlarged view of the muffler section.
F3D Pylon Racing Engines with some engines optimized for tuned pipes,
Peter Soule's documentation to learn more about the history of tuned pipes for model engines,
my Silencer Application software, including a similar tuned pipe designer.
Remark: to use JavaPipe in the standard way in your browser, over the internet, it is not necessary to perform the procedures described in this section. I cannot give much support to solve any problems occurring while running your local copy based on your local Java installation. If you have not already a working Java system on your machine, you might want to consult a computer guru.
If you want to run your local copy of JavaPipe , you can download a copy of the JavaPipe archive to your disk. You can also save the applet page to a local file, depending on the method you want to use for running you local copy.
last modification of this page: 21.08.01
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Copyright 1986-2001 Martin Hepperle
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