2 Components
The purpose of the Exhaust Gas Recirculation (EGR) System is to reduce engine emissions in accordance with Environmental Protection Agency (EPA) regulations.
The key components of an MBE EGR system consists of:
EGR Valves
EGR Cooler
Reed Valves
EGR Mixer
The MBE engines for NAFTA On-Highway 2004 applications use a liquid-cooled EGR system. Exhaust is routed from the exhaust manifold, through the EGR shutoff valve (MBE 4000 only), the EGR cooler, the EGR control valve, the reed valves (all except the MBE 906), and the EGR mixer in the intake manifold where they are mixed with the charge air. To view the arrangement of these components,
see Figure "Schematic of MBE 4000 EGR System"
for the MBE 4000 engine and
Figure "Schematic of MBE 900 EGR System"
for the MBE 900 engine.
Figure
, Schematic of MBE 4000 EGR System
Figure
, Schematic of MBE 900 EGR System
The addition of cooled exhaust gas back into the combustion airflow reduces the peak in cylinder combustion temperature. The formation of Oxides of Nitrogen (NOx) is less at lower combustion temperatures.
Reed valves are employed on all MBE engines except for model 906. In order to drive exhaust gas into the charge air, the pressure in the exhaust manifold must be higher than the pressure in the intake manifold. The pressure in the exhaust manifold changes over time, peaking when exhaust valves open. Exhaust passes through the reed valves during these pressure peaks. The reed valves permit transport of exhaust only during the time when the exhaust pressure is greater than the charge air pressure.
The EGR systems for the MBE 900 and MBE 4000 engines are similar but differ in their specific components. The EGR components are
listed in Table "EGR Components Featured on the MBE Engines"
.
Table
,
EGR Components Featured on the MBE Engines