Exhaust Gas Recirculation (Egr) System - Toyota 22R-E Service Manual

EG2–148

EXHAUST GAS RECIRCULATION (EGR) SYSTEM

To reduce NOx emissions, part of the exhaust gases are recirculated through the EGR valve to the intake manifold to lower the
maximum combustion temperature.
Engine
VSV
Coolant Temp.
Below 48SC
CLOSED
(118SF)
Above 52SC
OPEN
(126SF)
Remarks: *Pressure increases
** When the throttle valve is positioned above the R port, the EGR vacuum modulator will close the atmosphere passage
and open the EGR valve to increase the EGR gas, even if the exhaust pressure is insufficiently low.
ENGINE
Throttle Valve Pressure in the EGR
Opening Angle
Valve Pressure Chamber
Positioned below
EGR port
(1)
Positioned between
LOW
EGR port and R
(2)
port
HIGH
Positioned above
(3)
R port
HIGH
Modulator closes .EGR valve opens
EGR Valve closes Modulator opens
– EMISSION CONTROL SYSTEMS
EGR Vacuum
Modulator
*Pressure constantly
OPENS passage to
alternating
atmosphere
between low and
CLOSES passage to
high
atmosphere
CLOSES passage to
atmosphere
Pressure drops
EG R
Exhaust Gas
Valve
Not
CLOSED
recirculated
Note
CLOSED
Recirculated
Note
CLOSED
Recirculated
Recirculated
OPEN
Recirculated
OPEN
(increase)