Air Diverter Valve: Description and Operation

Two general types of Bypass Valves (normally closed and normally open) are used for air management within the MTA System. Both types perform the same functions and serve the same purpose of air management. The Bypass Valve is located within the vacuum hose routing between the air pump and the air check valves.


NORMALLY CLOSED BYPASS VALVES

Air Bypass Valves (Normally Closed):

With no or low vacuum being applied to the diaphragm chamber of a normally closed valve, pumped air is dumped to the atmosphere through silencer ports or a dump port. With a medium to high vacuum signal being applied, pumped air is directed into the exhaust system, during normal warm engine operation, short idles and light accelerations.


NORMALLY OPEN BYPASS VALVES
Normally open valves work in an opposite manner as the normally closed valve.

Normally Open Air Bypass Vales Without Vacuum Vent:

A normally open valve directs pumped air into the exhaust system when no vacuum is being applied to the vacuum chamber. With a minimum vacuum signal of 10" being applied to the signal port of a normally open valve, pumped air is dumped to the atmosphere.

Normally Open Air Bypass Valves W/Vacuum Vents:

Some normally open bypass valves are equipped with a vacuum vent nipple.