After treatment bypass for internal combustion engine during cold start and idle operation

An exhaust subsystem for use with an internal combustion engine comprising:

• a first exhaust path having a first aftertreatment system, the first aftertreatment system including at least a particulate filter;
• a second exhaust path parallel to the first exhaust path, the second exhaust path including an inlet coupled at a first junction to an upstream portion of the first exhaust path and an outlet coupled at a second junction to a downstream portion of the first exhaust path;
• a valve positioned to control exhaust flow through the second exhaust path;
• and
• a controller, in communication with the valve, configured to divert a portion of an exhaust flow from the first exhaust path to the second exhaust path responsive to an age of piston rings of the engine, where no other aftertreatment systems are positioned in the first exhaust path upstream of the first junction or downstream of the second junction.