Catalyst failure detection based combined ammonia to NOx ratios, conversion inefficiency values and ammonia slip values

摘要

Implementations of systems and methods for detecting the failure of an selective catalytic reduction (SCR) catalyst may include a controller or one or more circuits for acquiring an ammonia to NOx ratio (ANR) value for exhaust gas flowing through an exhaust system, acquiring a conversion inefficiency value indicative of a conversion inefficiency of the SCR catalyst, acquire an NH₃ slip value indicative of an amount of NH₃ slip through the exhaust system downstream of the SCR catalyst, calculate a combined ANR/conversion inefficiency/NH3 slip (ACN) value based on the ANR value, conversion inefficiency value, and NH₃ slip value, and indicating a failure of the SCR catalyst responsive to the calculated ACN value exceeding a predetermined threshold value.