Originally Posted by
wmazz
Are you trying to pick up a little extra acceleration by opening the rotary valve 6 deg earlier?
Is that why you added 5mm to the pipe?
What rpm are you trying to develop peak HP at? Or do you know what rpm your prop allows the
engine to rev up to. It would help if you posted a picture of the pipe and its length.
Did you figure out your transfer port timing? It would be helpful to know your BDT (blow down time).
The BDT will determine how effective your pipe is. If it is too mild, it will effect the pipe's performance.
Bill M.
Hello Bill,
My mind was to give up some acceleration, rc boat seldom accelerate, and want some more high end torque, rc boat mostly run at high rpm. After the mod. I believe that delay inlet close must accompanied with change in higher max. power rpm. I actually want more high end torque but not higher rpm.
Refer to article on
HOW TO TIME A FRV(CRANKSHAFT TIMING):
http://www.modelenginenews.org/techn...me.html
The inlet should open at BDC. But most nitro engine do open around 30 degree ABDC.
Refer to 2 stroke engine animation:
http://www.btorcboat.com/images/two-stroke_c_3.gif
Side port gasoline engine, with inlet reed valve,
start to draw fresh charge very soon after BDC, frame 19 of the animation. This is by the negative pressure generated by the pipe divergent cone. But this cannot happen in most nitro engine at the same angle. While the inlet not yet opened, the negative pressure establish a low pressure inside the crankcase. As the pulse reflect and inlet open, crankcase low pressure disappear. Don't konw the flow direction.
Refer to
www.modelenginenews.org. With half of the crankshaft structure removed, a weak crankshaft. I believe this O.S. Speed R2101 work very close to a side port gasoline engine:
http://www.osengines.com/engines-car...043/index.html
With sight of inlet late open. I mod. my engine to advance open by 6, hope to make it to work like side port gasoline engine. Delay close by 2, want more high end torque.
Boat pipes are narrow band. Long pipe give better low end, short pipe give better high end. None work like wide band car pipe. I tried the old pipe length but not work. Lengthen 5mm work.
I need some more testing before I knew that whether my aims were achieved.
Hope to hear any idea.
Best,
Leo