Methods and systems for reducing hydrocarbon emissions from an internal combustion engine. The engine's exhaust aftertreatment system has at least a particulate matter (soot) filter and means for actively regenerating the particulate matter filter. During operation of the engine, the soot loading state of the particulate matter filter is monitored. The filter is regenerated when required, but the regeneration is controlled so that the particulate matter filter retains a small level of soot loading. This soot "pre-loading" ensures hydrocarbon reduction during the next cold start.
Gary D. Neely; Darius Mehta