Forester F4-2.5L SOHC (2004)
2) Operation at the split point pressure
When pressure "P2" increases to the split point pressure, force "f2" is generated. (Piston's cross sectional area "A" has been selected so that the
force is generated starting with the split point pressure.) The pressure pushes the piston rightward, overcoming spring force "F". As a result, the
piston moves rightward and comes in contact with the lip seal, blocking the passage toward the rear wheel cylinders.
3) Operation after reaching the split point pressure
Immediately before the fluid passage toward the rear wheel cylinders is closed, pressure "P2" is slightly higher than pressure "P3". So the piston
can move in the spring force acting direction and the fluid can flow to the wheel cylinders. However, as soon as pressure "P2" becomes equal to
"P3", the passage closes.
This cycle is repeated as long as the pedal is depressed further, but pressure increasing rate of the rear wheel cylinders is smaller than that of the
front wheel cylinders.