Exhaust Gas Recirculation (Egr) System (7M-Ge - Toyota Supra 1990 Manual

EC-12
EMISSION CONTROL SYSTEMS - Exhaust Gas Recirculation (EGR) System (7M-GE)
EXHAUST GAS RECIRCULATION (EGR) SYSTEM (7M-GE)
EG R Port R Port
EGR
Vacuum
Modulator
EGR
VSV
(1 )
EGR Port
EC3633 EC2106
(2) (3)
EGR Port
EGR Port
EC2107 EC210B
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.
Coolant *Engine
VSV
Throttle Valve Pressure in the EGR EGR Vacuum EGR
Exhaust Gas
Temp. RPM Opening Angle Valve Pressure Chamber Modulator Valve
Below 57°C
OPEN
CLOSED
Not
(135°F)
recirculated
Above
OPEN CLOSED
Not
5,200 rpm
recirculated
Positioned below
CLOSED
Not
EGR port recirculated
Above 63°C
(1)
** Pressure con·
OPENS passage
CLOSED
Not
(145°F)
Below
Positioned be-
LOW
stantlyalter-
to atmosphere recirculated
CLOSED tween EGR port
4,800 rpm
and R port
(2)
nating between CLOSES passage
HIGH
low and high
to atmosphere
OPEN Recirculated
Positioned above
(3)
CLOSES passage
OPEN
Recirculated
R port HIGH to atmosphere (increase)
Engine RPM control is for Calif. only.
Pressur
1
increase~
Modulator closes
~EG
R valve opens
~Pressure
drops
L. - - - - -
EG R valve
close~
Modulator opens -
I
When the throttle valve is positioned above the R port, the EG R vacuum modulator wi II close the atmosphere
passage and open the EGR valve to increase the EGR gas, even if the exhaust pressure is insufficiently low.