Originally Posted by ziggy12345
More info on pipe length
The tuned pipe length is the distance from the exhaust outlet along the centreline of the manifold to the middle of the diverging cone on the end. This distance is calulated by using Lt = (Eo x Vn)/N
Where:
Lt is the Tuned Length in Inches
Eo is the Exhaust Timing in Degress
Vn is the gas velocity (1700 ft/sec)
N is the Crank RPM
So for 152 deg exhaust timing (Is that right?) and RPM of 37,000 (Most .12 engines peak around there) you get a tuned length of 6.9"
I just measured my 2630 pipe and the length is around 5.9 to 6" so the pipe is tuned for just over 43,000 and thats way to high. I need to add an inch of manifold length to bring it to 37,000 rpm!! I'll try it out and see what happens
Cheers
every theory on 2-stroke engines are complicated.........
if you check the RPM at peak power of any engine the the piston displacement, you can estimate the carburettor venturi..............
I tried the formula and there is a constant K which is supposed to be around 0.8~0.9 according to the author
here follows the formula:
carb diameter = K * SQROOT(piston displacament in liters * rpm at peak power)
try it out for every engine you know and you will conclude 2 things.......
the formula or the K constant are completely wrong for small high performance 2 storke glow engines............or the engines are designed wrognly..........
what I mean is that theories can lead us to very confused thoughts.......
besides pipe lenght, the chamber geometry has a lot to do with engine performance and powerband, so I am sure that the lenght you have calculated is way far from the ideal, not to mention that 1 inch longer than the EFRA 2630 pipe will be more than enough to make impossible turning to the left.........