Fast-paced action is guaranteed with the GraviTrax Element Looping. How fast do the balls have to be to defy gravity?

The looping element turns the world of balls upside down for a brief moment. The balls fly through the loop at breakneck speed, overriding gravity for a moment. Combined with any GraviTrax Starter-Set, the Looping element turns the balls in the marble run upside down. How much momentum does the ball need to make it through the loop?