When the restriction is too high, some engines inject fuel up stream of the filter, others richen the fuel to the injectors, and this raises the exhaust temp and causes the soot to burn off the face of the catalyst face inside the particulate filter. The particulate filter collects the soot, and has sensors to measure input and output pressure difference, and temp sensors. With DEF the system requires less regenerations. With the DEF system there is more nitrous oxide, but less soot. The next system has the particulate filter and another chamber where the Diesel Exhaust Fluid is injected. This has to do with injection timing and EGR valve timing. ![]() But what I was taught is the earlier versions with particulate filter only, made more soot(particulate), but less nitrous oxides(NOX), which is a big concern with air pollution. ![]() I retired (truck mechanic)a few yrs after the diesel after treatment came out.
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