After playing with it a lot, I figure that it has something to do with accelerating in the other direction as well as entering a new screen. I have no idea why. The reason I think this is because the speedboost (or more likely, slowdown) you get when performing it is variable. Sometimes you slow down a lot, sometimes only a little. Sometimes you stay the same speed, and sometimes you go much faster. I observed this in the falling boxes room just by seeing about how far I got on various attempts.
I believe that not only do you have to hold both left and right upon entering a screen, but you have to be at just the right point of a turn-around for the speed boost to happen. I have yet to get the speed boost while not stopping beforehand.
I was playing around in the tower room and it turns out you can make a faster cycle with LintRunner's speed glitch. Each faster cycle saves a second. Here's the link:
