Somerset Regal L4-151 2.5L (1985)
Fig. 5 Typical diverter air bypass valve w/pressure relief valve
The diverter or air bypass valve, Figs. 4 and 5, when triggered by a sharp increase in manifold vacuum, shuts off the injected air to the exhaust and
prevents backfiring during this richer period. On engine overrun the total air supply is dumped through the diverter valve muffler. At high engine speeds
the excess air is dumped through the pressure relief valve located either in the pump assembly, Fig. 3, or the diverter valve, Fig. 5.
The check valves prevent hot gases from backing up into the hoses or pump,yet allow fresh air to circulate from the pump to the exhaust ports.