Expansion chamber , but needs research & development

[fastboy9]

Just found another expansion chamber design program, this ones an internet based java program you can use. Another bike builder has created a stunning bike and exhaust using this software.

Heres the link:
http://www.mh-aerotools.de/airfoils/javapipe_main_en.htm

 

[Simon_A]

Nice find mate.

 

[wildemere]

Exhaust port angle is the crankshaft angle after TDC when the exhaust port opens.

Measured with a degree wheel or protractor.

 

[runslikeapenguin]

Exhaust port angle is the crankshaft angle after TDC when the exhaust port opens.

Measured with a degree wheel or protractor.

im pretty sure when its asking for that its talking about the floor of the exhaust port in relation to the cylinder wall.

 

[MotorBicycleRacing]

im pretty sure when its asking for that its talking about the floor of the exhaust port in relation to the cylinder wall.

http://www.mh-aerotools.de/airfoils/javapipe_main_en.htm

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). See also here.
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.

 

[djase10]

Thanks Fastboy9

 

[runslikeapenguin]

http://www.mh-aerotools.de/airfoils/javapipe_main_en.htm

well that's what i though at first but why would they not just ask for the exhaust port timing duration, and why use the word angle and not ask for the degrees like the timing is measured by. i could be wrong but i remember when i was entering in the information that when i was entering info into the program for that slot it told me it would only except numbers within a certain range and i remember then being really small.

like i said however i could be wrong.

 

[Old Bob]

I think the term angle is universal among authors, I've seen the term used by Jennings,Bell and Blair in their books.
I can see why they use angle instead of duration, if discussing disc valve induction, you can have asymetrical opening and closing points in crankshaft degrees, in this case simply using duration figures would not be accurate.
The key thing is which angle they are reffering to. The MOTA free pipe designer is based on Blairs software and it uses the angle from TDC to exhaust port open as the input value, where Martin Hepperles software uses the duration and inputs that value expresed as angle.
One thing to remember when using Martins program* is that EGT temp is in Kelvin. Which is Celsius + 273.15.
Most of the authords recommend using EGT between 500 and 650 C.For a street ridden bike I would use the lower 500 C value.While the pipe temp itself does influence wave motion inside, the real temp we are looking for is the exhaust gas temp inside the pipe, the speed at which pulse waves travel are regulated by the gas temp.
As noted by Jennings, Bell and Blair the pipe formulas are a starting point, not the last word in pipe design for a particular set of parameters.So if you a little off with EGT there are probably other areas of the pipe design that could use some tweaking.For us average working stiffs, putting the pipe on an adjustable length header so we can tune the length works well enough.

*added my version of Martin Hepperles program is older, I'm not sure what the newer program looks like as my computer doesn't support the java needed to run it

 

[runslikeapenguin]

i am wrong, it is the duration, i talked to my 2 stroke pro and he said that Angle is more of a European term for the same thing. it is the total degrees for the duration.

 

[Old Bob]

Makes sense, most of the writers are Brits I beleive.I know Gordon Blair is.

A google search for Gordon Jennings Two Stroke Tuner's Handbook will turn up copies in .pdf format.Although a little dated, the book is still reconginzed as "the bible"