Air Bypass Valves - Description and Operation
is maintained between the signal port and the vent port. The signal port must have 3 inches Hg more vacuum than the vent port to hold the dump. This
mode is used to protect the catalyst from overheating.
Normally open valves without a vacuum vent, Fig. 59, provide a timed dump of air for 1.1 or 2.8 seconds when a sudden high vacuum of about 20
inches Hg is applied to the signal port. This prevents backfire during deceleration.
