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A number of changes occurred in this EGR system from its introduction in 2002. Older versions of this engine (US EPA 2002/2004) had the EGR valve located on the inlet side of the EGR cooler. Early versions used a pneumatically actuated valve that was replaced with a hydraulically actuated valve and finally, the electrically actuated valve shown in Figure 1. Some versions also used pressure taps upstream and downstream of the EGR control valve to monitor the pressure differential across the valve for EGR rate feedback instead of a venturi-type flow meter. By 2008, the venturi flow meter was removed entirely.

Another example of a cooled EGR system for heavy-duty engines is the Scania Euro IV system illustrated in Figure 2. Pre-turbine (HPL) exhaust is routed via an EGR control valve and an EGR cooler to the engine inlet system. Engine jacket water is used as the cooling medium in the EGR cooler in this example as well. In general, EGR can be cooled with engine coolant, ambient air or a low temperature liquid.