The larger the total differential controls the amount of flare of the and the intermediate differential controls how quickly the drilled ball reacts to lane friction. The higher the total differential, the more the ball flares which causes the ball to react sooner. The higher the intermediate differential, the quicker and sharper the ball reacts to lane friction when it encounters it.
I'm no expert on this subject,so I hope this helps>
Justin Wi Wrote
P1 -20% differential
P2 No change
P3 +20% differential
P4 +40% differential
These placements effect both the total diff and intermediate diff, so they modify diff ratios as well.
A P1 hole decreases differential which reduces flare and dynamic instability, which promotes energy retention. If a ball expends less energy flaring, it will have more to release when it sees friction.
A P3/P4 hole increases the differential which increases flare and dynamic instability, which promotes an earlier release of energy. If a ball is flaring more, it bleeds energy sooner and has a smoother response to friction.
In practice with the equipment of today, you have to get your initial layout close, and then fine tune with a balance hole. A balance hole can help, but not always fix, a bad initial layout. I have seen that a P1 increases backend when a ball checks early, and a P3/P4 placement promotes earlier and smoother, which can end up hooking more overall in some situations.
I also have an alternate position that I use in certain cases. 2" down the VAL from PAP, but only on symmetrics. Sometimes when I want a Sym to roll sooner, I place this hole. The drilled PSA shifts towards the hole and decreases the final drilling angle. P3 and P4 holes in syms give them more of an asymmetric type of roll.
Angela Wilt:MOTIV Staff Member