Subaru 1600 Service Manual page 184

6) Anti-afterburning System
During rapid deceleration the air-fuel
mixture becomes heavily concentrated
temporarily, as the vacuum pressure in
the intake manifold increases, causing
fuel residue on the inside wall of the
manifold to vaporize and to enter the
combustion chamber.
The anti-afterburning system prevents
this heavy concentration from occur-
ring by introducing air into the intake
manifold at this time. This prevents
afterburning in the exhaust system.
During constant-speed running, the
valve is closed because chambers
®
and
@
are at the same pressure. In
deceleration (when the throttle valve is
closed), the vacuum pressure in the
intake manifold increases and the
pressure in chamber
@
decreases.
The diaphragm is forced down to open
the valve. This permits outer air to be
drawn into the intake manifold
through the filter.
After that, the pressure in chamber
®
gradually becomes equal to that of
chamber
@
as the air flows through
the orifice. The diaphragm is then
pushed up by the spring, which in turn
closes the valve to stop the suction of
air.
I Air passage
2
Anti-afterburning
valve
3 Orifice
4 Intake manifold
5 EGR valve
6 Vacuum line
®
\
®
A 10-191
Fig. 5-31 Anti-afterburning system
7) Shift-up Control System
Shift-up control system is provided
on automatic transmission vehicle only
and is used to reduce CO emission due
to rapid warm-up.
If
the engine is started while the
coolant is in the preset temperature
range, ECM keeps the automatic trans-
mission in a kick-down state for a
certain duration of time.
EMISSION CONTROL SYSTEM
Air
Fig. 5·32 Anti-afterburning valve
Orifice
To intake
manifold
To ignition-starter switch
~.-------~------------~-------,
To battery
- - - - - - ' 1 ' - - - - - - ,
A10-192
Electronic control
module
Fig. 5-33
Kick-down
switch
Kick-down
solenoid valve
Ignition coil
Relay
r 6
Intake manifold
LJ--
A10-193