Since the latter part of 2002, cooled exhaust gas recirculation systems have been the primary technology path used by many engine manufacturers to reduce NO{sub}x emissions in on-highway and even some off-highway engines. And with the newly implemented 2007 EPA emissions standards, EGR rates on heavy-duty truck engines are higher than they've ever been. While good for reducing emissions, the increased EGR flows also increase the amount of unburned hydrocarbons and other particulates being recirculated back into the engine. This could potentially have an impact on components such as EGR valves, which regulate the flow of gas into the EGR cooler. More particulate deposits could literally gum up the works of an EGR valve, which could potentially impact the careful working choreography of the entire system.
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