It would seem to me that the fairly arbitrary definitions of a turn/curve/bend/kink are such that it would be impossible to ever actually establish a "number per lap".  And, I'm assuming the original question pertained to race speeds on a closed course.  To me, any deviation from my current line which would cause me to have to either change the lean angle of the bike (especially from upright), or back off the throttle, or both, (not including changes in the road surface/elevation) would qualify as a change in direction and therefore a "turn/curve" to me.  Just my two cents.