I too am trying to understand how hole size represents hp, but I also know that one hp level can have different amounts of holes and sizes. It comes down to quality, spray pattern, and atomazation (can't spell) of the injector. Just because it has more or bigger holes doesn't always mean it will put more power down to the ground. When comparing one set to an other of the same brand, there will be a coralation of hp to hole size. But when comparing brand to an other brand there could be a differance between hole size and hp. This is what I understand from what I have read. If I am way off, some one set me stright.