DDEC IV Components
The primary purpose of the EGR system is to reduce engine exhaust gas emissions in accordance with EPA regulations by allowing a percentage of the exhaust gases to remix with the air coming into the intake manifold. Engine exhaust gases will dilute the incoming air by displacing some of the oxygen in the air being supplied through the intake manifold. Less oxygen results in a slower fuel burn which reduces the peak cylinder temperature permitting reduced nitrogen oxides (NOx) emissions. Figure "EGR System" illustrates how the components of a EGR system function.
Figure 1. EGR System
1. EGR Valve Actuator
5. EGR Gas Delivery Pipe
8. EGR Cooler
2. VNT Actuator
6. S Pipe
9. High Flow Water Pump
3. VNT Turbocharger
7. EGR Valve
4. Delta Pressure Sensor
Figure 2. Pre-2004 Right Side View
1. EGR Gas Delivery Pipe
4. Intake Manifold Air Temperature Sensor
2. EGR Mixer
5. Barometric Pressure Sensor
3. Intake Manifold
6. Turbo Boost Pressure Sensor
Figure 3. Pre-2004 Left Side View
An enhancement program has been launched to upgrade production 2004 DDEC IV EGR engines. For detailed information, please visit the Detroit Diesel Technical Information Web Page at http://220.127.116.11/public/sp/spnav.asp and browse for 18SP597. Figure "Enhanced DDEC IV 2004 EGR Engine" illustrates some of the enhancements such as tube and shell EGR cooler, redesigned delivery pipe, EGR valve, and venturi tube.
Note: You may also access 18SP documents after logging into the DDC Extranet by clicking on Support, On-Highway, Service Information, Special Publications (18SPs).
1. Tube and Shell EGR Cooler
3. Delivery Pipe
2. EGR Valve
4. Venturi Tube
Figure 4. Enhanced DDEC IV 2004 EGR Engine
FUNCTIONALITY OF THE EGR COMPONENTS
This section will present and discuss specific EGR components which collectively as a system allow the engine to meet emission standards.
DDEC IV Electronic Control Module
The Electronic Control Module (ECM) is the backbone for engine management. The ECM receives electronic inputs during vehicle operation via engine and vehicle mounted sensors.
Refer to Appendix "10.4.7 DDEC IV ECM Overview and Vehicle Interface Harness" for a view of the DDEC IV ECM and related harness connectors.
DDEC IV ECM engine management benifits are:
- Excellent engine performance
- Optimum fuel economy
- Emission levels that meet current laws without after treatment
- Engine diagnostics
- Simple programming
Variable Pressure Output Device (VPOD)
There are two VPODs which control the VNT and EGR valve. See Figure "EGR Valve and VNT Control System" . The location of the VPODs are application dependent.
Two system components are required for proper operation of EGR valve and VNT control system.
- 12V or 24V power supply
- DDEC IV ECM: PWM#2 (Y1) EGR and PWM#4 (X2) VNT
Figure 5. EGR Valve and VNT Control System
During engine EGR operation, the VPODs provide modulated air pressure to the pneumatic actuators which change the position of the VNT vanes and the position of the EGR valve. The results of the VNT vanes being able to adjust are:
- Enhanced air/fuel ratio during engine acceleration
- A proper mix of exhaust gas with intake charge air
- More vane closure increases the EGR flow rate (PWM % is high).
- Less vane closure decreases the EGR flow rate (PWM % is low).
- Enhanced engine brake capability.
The following conditions are present when vane positions are at 90% PWM. See Figure "Maximum Regulated Air Pressure to the VNT"
- Regulated air pressure to the VNT actuator from the VPOD is at the maximum.
- Regulated exhaust restriction is at the maximum.
- EGR flow is at maximum while operating in EGR mode
Figure 6. Maximum Regulated Air Pressure to the VNT
The following conditions are present when the vane positions are at 50% PWM. See Figure "Regulated Air Pressure to the VNT"
- Regulated air pressure is supplied to the VNT actuator from the VPOD
- Exhaust gas restriction is moderate
- EGR flow is increased while operating in EGR Mode
Figure 7. Regulated Air Pressure to the VNT
The following conditions are present when the vane positions are at 7% PWM. See Figure "No Air Pressure to the VNT"
- Air pressure is not supplied to the VNT actuator from the VPOD
- Exhaust gas restriction is minimal
- EGR flow is minimal while operating in EGR Mode
Figure 8. No Air Pressure to the VNT
Variable Nozzle Turbocharger
Variable nozzle turbocharger (VNT), see Figure "Variable Nozzle Turbocharger" , uses a high pressure pneumatic actuator to regulate and control turbine vanes. There is no wastegate with this system. The VNT actuator is mounted on a bracket attached to the turbocharger and receives air pressure from engine-mounted VPODs. VNT actuator connects via a rod to the pin joint of the turbine external arm. Rotation of external arm simultaneously rotates several pivoting nozzle vanes positioned inside turbine housing at the outer periphery of turbine wheel. This adjusts turbocharger speed, boost and EGR flow in accordance with DDEC engine management control.
Note: VNT actuator is spring loaded. If air pressure is lost the actuator will open the VNT vanes resulting in low/no boost.
Figure 9. Variable Nozzle Turbocharger
Turbocharger Boost Sensor
Turbocharger Boost Sensor (TBS), see Figure "Turbocharger Boost Sensor" , is used to monitor air pressure in the intake manifold. DDEC IV uses this air pressure data for fuel management during engine acceleration. The TBS sensor is supplied a 5-volt reference signal by ECM and returns a voltage signal to the ECM relative to turbo boost pressure. Return voltage increases as boost pressure increases. Operating values are 0.10-5.0 V during normal engine operation.
Figure 10. Turbocharger Boost Sensor
EGR valve position is controlled by the ECM. The ECM continuously monitors all engine operation modes and performs self diagnostic checks of RPM, load, altitude, air temperature, etc. and uses this information to determine the EGR valve position. The ECM changes EGR valve position by regulating air pressure output from the VPOD to an actuator mounted to EGR valve. The EGR valve outlet is connected to the EGR cooler and recirculates a fraction of the engine exhaust gases to the intake manifold for purposes of engine emission control. When the EGR valve is closed, exhaust flows from the exhaust manifold, past the turbine wheel into the VNT and out exhaust system in traditional way. See Figure "Pre-2004 EGR Valve" to view a pre-2004 EGR valve and see Figure "Enhanced EGR Valve" to view enhanced EGR valve.
Note: The EGR actuator is spring loaded. If air pressure is lost the actuator will close the EGR valve resulting in no EGR flow.
Figure 11. Pre-2004 EGR Valve
Figure 12. Enhanced EGR Valve
EGR Valve Actuator
The EGR valve actuator (see Figure "EGR Valve Actuator" ) regulates EGR butterfly valve.
Figure 13. EGR Valve Actuator
The primary purpose of an EGR cooler is to cool exhaust gases. Coolant that flows through the cooler removes heat from exhaust gases that enter the EGR cooler. See Figure "Pre-2004 EGR Cooler and Enhanced EGR Cooler" . See Figure "View of Current EGR Cooler" for a view of the current EGR cooler.
1. Pre-2004 EGR Cooler
2. Enhanced EGR Cooler
Figure 14. Pre-2004 EGR Cooler and Enhanced EGR Cooler
Figure 15. View of Current EGR Cooler
Cooling is accomplished by directing exhaust gas past the cooling tubes in the EGR cooler. The EGR cooler core transfers the heat from the exhaust gases to the engine cooling system as the gases are sent to the EGR/charge air mixer. The gases are then mixed with incoming air from the charge air cooler before being sent to the intake manifold.
Delta P Sensor
The Delta P Sensor monitors the pressure differential across the venturi (in the EGR delivery pipe at the EGR cooler outlet) and uses the delta pressure and exhaust temperature to determine the rate of EGR flow. See Figure "Delta P Sensor" . The sensor is supplied a 5-volt reference signal from the ECM and returns a voltage signal to ECM relative to pressure difference across the Venturi tube. Return sensor voltage increases as pressure differential increases during engine operation (operating values are 0.23-4.77 V).
1. Thermostat Housing
2. Delta P Sensor
Figure 16. Delta P Sensor
Venturi Tube/Delivery Pipe
A Venturi tube with a port at each end is attached to the EGR delivery pipe at the EGR cooler outlet. The ports are connected to the Delta P Sensor to monitor the pressure differential across the venturi as EGR gases flow through EGR delivery pipe to the charge-air mixer. See Figure "Pre-2004 Delivery Pipe" to view pre-2004 delivery pipe and see Figure "Enhanced Delivery Pipe" to view enhanced delivery pipe. The ECM uses this information along with temperature and density of exhaust gases to determine precise EGR mass flow rate. See Figure "Pre-2004 Venturi Tube" for pre-2004 venturi tube and see Figure "Enhanced Venturi Tube" for enhanced venturi tube.
Figure 17. Pre-2004 Delivery Pipe
Figure 18. Enhanced Delivery Pipe
Figure 19. Pre-2004 Venturi Tube
Figure 20. Enhanced Venturi Tube
EGR Temperature Sensor
ECM uses the EGR Temperature Sensor to monitor exhaust gas temperatures in the EGR delivery pipe and uses exhaust temperature and delta pressure across the Venturi tube to determine rate of EGR flow. Temperature sensor is supplied a 5-volt reference signal from the ECM and returns a voltage signal to the ECM relative to exhaust gas temperatures in the EGR delivery pipe. Sensor return voltage decreases as exhaust gas temperature increases (sensor operating values are 0.10-5.0 V). See Figure "EGR Tempertaure Sensor" to view the sensor with connector.
Figure 21. EGR Tempertaure Sensor
The EGR air mixer combines exhaust gases with the fresh air supply flowing from the charge air cooler. Once the air has passed through the EGR mixer, the intake manifold diffuses EGR gases evenly to each cylinder. Sensors are mounted within the intake manifold to monitor air temperature and boost pressure. See Figure "Pre-2004 EGR Mixer" for a view of the pre-2004 EGR mixer and see Figure "Enhanced EGR Air Mixer" for a view of the enhanced EGR mixer.
Figure 22. Pre-2004 EGR Mixer
Figure 23. Enhanced EGR Air Mixer
Charge Air Cooler
The Charge air cooler (CAC) is mounted in front of the cooling system radiator which is connected to the turbocharger and the intake manifold. Compressed air leaving the turbocharger is directed through the CAC before it goes to the EGR air mixer to be mixed with EGR exhaust gases entering the intake manifold.
Cooling is accomplished by incoming fresh air flowing past the tubes and fins of charge air cooler. Compressed intake charge air flowing inside the CAC core transfers heat to the tubes and fins where it is transferred to the outside air.
The CAC is used to the reduce temperature of the compressed air leaving the turbocharger before entering the intake manifold allowing for a more dense charge of air to be delivered to engine.
Turbocharger Compressor Inlet Temperature Sensor
Turbocharger Compressor Inlet Temperature Senor (TCI) is a DDC part and is installed by the truck manufacturer within piping between the air filter and turbocharger inlet. The TCI sensor which is used to control EGR operation in high humidity and heat conditions that may cause damage to the engine is monitored by DDEC. The ECM will log a fault code for one or more functions of this sensor. Each sensor mode is supplied a 5 V reference signal by the ECM and returns a voltage signal to the ECM relative to temperature and humidity. Return voltage from the TCI sensor increases as atmospheric humidity increases and return voltage decreases as air inlet temperature increases.
The TCI operating values during normal engine operation are 0.23-4.93 V.
High Flow Water Pump
The EGR engine uses a high flow water pump to improve the coolant flow for added heat dissipation.
Note: The high flow water pump is not interchangeable between EGR and non-EGR engines.
|Series 60 EGR Technician's Manual - 7SE60|
|Generated on 10-13-2008|