Vacuum Advance Unit

Vacuum Advance Unit:

A vacuum advance unit changes the timing, depending on engine load (intake manifold vacuum), by moving the base plate including Hall sender. The unit is mounted on the side of the distributor

CONSTRUCTION
The vacuum advance unit consists of a spring loaded vacuum diaphragm, the spring, diaphragm rod, vacuum connection and hose. The diaphragm rod is connected to the base plate. The vacuum for the advance unit is taken from just before the throttle valve.

OPERATION
As manifold vacuum increases (high load), the diaphragm compresses the spring and moves forward. This moves the diaphragm rod and changes the position of the base plate with the Hall sender mounted to it. This change is in opposite direction of rotor rotation, the Hall effect signal is now triggered earlier and therefore the timing gets advanced.