03-08-2
Engine Emission Control
03·08·2
DESCRIPTION AND OPERATION (Continued)
Exhaust Gas Recirculation (EGR) System
The exhaust gas recirculation {EGA) system is
designed to:
•
reintroduce exhaust gas into the combustion cycle.
•
lower combustion temperatures.
•
reduce the formation of nitrous oxide {N20).
The amount of exhaust gas reintroduced and the
timing of the cycle varies by calibration.
liming and volume are controlled by the following:
•
engine rpm
•
engine vacuum
•
exhaust system backpressure
•
engine coolant temperature
•
throttle position
The EGA valve {EGA valve){9D475) is vacuum
actuated. The vacuum hose routing diagram is shown
on the vehicle emission control information decal.
The EGA system is a differential pressure feedback
EGA system. Differential pressure feedback EGA is a
subsonic closed loop EGA system. The differential
pressure feedback EGA system:
•
monitors EGA flow rate by the pressure drop across
the metering orifice.
•
uses an EGA backpressure transducer as the
feedback device.
•
controlled pressure is varied by the valve movement
_
using vacuum output of the EGA vacuum regulator
solenoid.
•
uses the EGA valve only as a pressure regulator
rather than as a flow metering device.
•
allows for a more accurate assessment of EGA flow
requirements.
Differential Pressure Feedback EGR Flow Diagram
e
Part
Item
Number
1
-
2 12A650
3
-
4 9J459
5
-
6
-
7
-
8
-
9
-
10
-
11
-
12
-
13 9J460
14
-
15 90475
V9925-A
D
es
cripti
o
n
Analog Voltage Input
Powertrain Control Module
Duty Cycle Output
EGA Vacuum Regulator
Solenoid
Vacuum Source
Intake Vacuum
EGRFiow
Metering Orifice (Part of
90475)
Exhaust Flow
Exhaust Pressure
Exhaust Pressure Input
Controlled Pressure Input
EGA Backpressure
Transducer
Vacuum Output
EGA Valve
1 997
Thunderbird. Cougar July
1996