D:04:08
Fuel,
Emission and Exhaust System
When the frequency valve is open, the fuel
pressure in all of the lower chambers will be
reduced by allowing some of the fuel to return to
the tank. When the lower chamber pressure is
reduced,
the diaphragm downward movement will
increase the passage opening to the injectors. This
will increase the volume of fuel being injected to
the engine, enrichening the mixture. When the
frequency valve closes, the pressure in the lower
chambers will return to normal and the diaphragm
will return to its original position.
(Fig.
26—27)
The frequency valve operates at 70 cycles per
second.
The length of time the valve
is
held open
during each cycle depends on the pulse ratio
supplied by the Lambda ECU module.
The pulse ratio is the frequency valve open
time
versus closed time during one cycle of operation. A
pulse ratio of 80/20 means that the frequency valve
Lower Chamber
of Fuel Distributor
tin
Fig
26
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