ENGINE SYSTEMS Electrical System The MBE 900 engines for on-highway EPA 2007 regulation applications use a cooled EGR system along with an Aftertreatment System to meet the emission standards. The electrical system consists of a starting motor, starting switch, battery-charging alternator, storage batteries, and the necessary wiring. Exhaust System 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. Exhaust gases exit the cylinders through exhaust ports and the exhaust manifold. These exhaust gases expand through the exhaust turbine and drive the turbocharger compressor impeller. The gases are then released through the exhaust pipes and the aftertreatment device to the atmosphere.
Exhaust Gas Recirculation System 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. The EGR system consists of an EGR cooler, EGR valve, and an EGR mixer. 60 All information subject to change without notice. (Rev.
04/08) DDC-SVC-MAN-0040 0704 Copyright © 2008 DETROIT DIESEL CORPORATION