Minecraft Timer

Does anyone know where the timer or main loop is? I want to build in some acceleration with a EntityMob.motionY instead of just launching them at 2.5 from the start.

Context in this tutorial:https://www.youtube.com/watch?v=JtBBhhw6Y4Y&list=PLrnh7I7rzm5zvPDCW6eGWhTVQh3BPh2bu