Chemical reactions take time. So the alky has to be introduced early enough to have time to work, but not long enough for it to fall out of suspension, for the particles that are atomized, instead of vaporized. There are two parts to alky, atomization, and vaporization. Each have their own benefits, and way of optimizing them. Looking at who's going fast, and copying that, is a pretty good way of guaging what works.
