Toyota Supra 1990 Manual page 168

EC-16 EMISSION CONTROL SYSTEMS - Exhaust Gas Recirculation (EGR) System (7M-GTE)
EXHAUST GAS RECIRCULATION (EGR) SYSTEM (7M-GTE)
(2)
~
I
EGR Cooler
!
ECU
EGR Vacuum
Modulator
EG R Port
(1)
EGR Cooler
i
EC3330
EC2359
EGR Port
Vacuum
Modulator
EC2328
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
VSV
Throttle Valve Pressure in the EGR EGR Vacuum EGR
Exhaust Gas
Temp. Opening Angle Valve Pressure Chamber Modulator Valve
Below 57°C
CLOSED
Not
(135°F)
(E-G)
-
- -
CLOSED
recirculated
Positioned below
(1)
CLOSED
Not
EGR port
- -
recircu lated
Above 63°C OPEN
(145°F)
(E-G)
Positioned above
* CLOSES passage Recirculated
EGR port
(2)
to atmosphere
OPEN
(increase)
*
When the throttle valve is positioned above the EGR 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.