Yamaha Sirius T110LSE, Service Manual

Page: 191 / 308

CARB
AIR INDUCTION SYSTEM
5-10
EAS00507
AIR INDUCTION SYSTEM
AIR INJECTION
The air induction system burns unburned
exhaust gases by injecting fresh air (secondary
air) into the exhaust port, reducing the emission
of hydrocarbons.
When there is negative pressure at the exhaust
port, the reed valve opens, allowing secondary
air to flow into the exhaust port. The required
temperature for burning the unburned exhaust
gases is approximately 600 to 700 °C.
EAS00508
AIR CUT-OFF VALVE
The air cut-off valve is operated by the intake
gas pressure through the piston valve
diaphragm. Normally, the air cut-off valve is open
to allow fresh air to flow into the exhaust port.
During sudden deceleration (the butterfly valve
suddenly closes), negative pressure is generat-
ed and the air cut-off valve is closed in order to
prevent after-burning.
Additionally, at high engine speeds and when
the pressure decreases, the air cut-off valve
automatically closes to guard against a loss of
performance due to self-EGR (Exhaust Gas
Recirculation).
1
During normal operation, the air cut-off valve is
open.
2
During sudden deceleration (the butterfly valve
suddenly closes), the air cut-off valve closes.
3
At high engine speeds and when the pressure
decreases, the air cut-off valve is open.
å
From the air filter case
∫
To the cylinder head
ç
To the intake manifold
å
1
2 3
∫
ç
3S3-F8197-E0_5 05.11.2 16:58 Page 10