sharp edge in coupler..hamper performance?
long answer: the air rides along the inner wall of the pipe, if there's a sudden discontinuity (say a very sharp turn) the air will speed straight off that surface (imagine a car driving off a cliff vice hugging the ground over the top of a hill) and into the opposite side of the tube thus hampering flow through the entire section of pipe.






Bends over 45 degrees really start to affect flow. Bends with 90 degrees or more is real bad unless the radius is equal to or greater than the diameter of the tube.