Civic Hatchback L4-1493cc 1.5L SOHC (D15B1) TBI (1990)
Tandem Valve: Description and Operation
Fig. 45 Air Intake Tandem Control System
The tandem valve is employed to improve atomization of fuel which is injected by the main fuel injector in response to various engine operating
conditions.
When the tandem valve control solenoid valve, mounted underneath the air intake chamber, is de-activated, vacuum is not applied to the diaphragm
chamber of the tandem valve control diaphragm, so the tandem valve is nearly closed. The narrow clearance between the tandem valve and the inner
wall of the throttle body generates a rapid air flow which promotes atomization of the injected fuel from the main fuel injector.
When the tandem valve control solenoid valve is activated, vacuum is applied on the tandem valve control diaphragm and the tandem valve is opened in
response to vacuum which represents the air flow rate through the venturi. Therefore good atomization of the injected fuel is provided regardless of the
air flow rate.