Operators Manual

Table Of Contents
Exhaust Gas Recirculation System
The Exhaust Gas Recirculation (EGR) system consists of an EGR cooler, EGR
valve and actuator. The EGR actuator opens and closes the EGR valve to allow hot
exhaust gas to enter the EGR cooler. Heat is extracted from the exhaust gas,
resulting in cooler exhaust gas to the cylinders. EGR lowers the temperature of the
exhaust from the engine, therefore, reducing exhaust gas emissions to acceptable
levels.
The purpose of the Exhaust Gas Recirculation System (EGR) is to reduce engine
exhaust gas emissions in accordance with EPA regulations.
The EGR system has been optimized to dramatically cut NOx formation by routing
a measured amount of exhaust flow to the cylinders to lower combustion
temperatures. Lower temperatures result in lower NOx levels without the negative
effects of retarding engine timing. The EGR valve has been moved to the top of the
engine for improved serviceability.
Engines for on-highway EPA 2007 regulation applications use a cooled EGR
system along with an Aftertreatment System to meet the emission standards.
On the 260 - 350 horsepower engines, the EGR is fed by all six cylinders. The low
horsepower engines use an asymmetric turbocharger with two entries, and the EGR
is fed from the first three cylinders, taken from a small entry. The exhaust with a
maximum exhaust gas temperature of 730°C (1346°F) is cooled to a maximum of
150°C (302°F) in the EGR cooler. The cooled exhaust gases then pass through the
EGR valve and added to the mixer housing. The addition of cooled exhaust gases
back into the combustion airflow reduces the peak cylinder combustion
temperature. Less oxides of nitrogen (NOx) are produced at lower combustion
temperatures.
DD Heavy Duty Platform Operators Manual
All information subject to change without notice. 83
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