Methods and systems are provided for removing moisture from an engine exhaust system. In one example, a method includes, during a vehicle key-off condition, in response to a higher than threshold exhaust moisture level and a lower than threshold engine run time during an immediately prior drive cycle, operating an electric air compressor to remove the moisture accumulated in the exhaust manifold.

Methods for monitoring thermal characteristics of oxidation catalyst (OC) catalytic composition(s) (CC) are provided, and comprise communicating exhaust gas to the OC, and determining a temperature change of the CC for the time frame based on a plurality of heat sources including heat imparted to the CC from exhaust gas enthalpy, heat imparted to the CC via oxidation of HC and/or CO in exhaust gas, heat imparted to the CC via water present in the exhaust gas condensing on the CC or heat removed from the CC via water evaporating from the CC, and optionally heat exchanged between the CC and the ambient environment. Heat imparted to the CC via water condensing on the CC can be determined using an increasing relative humidity proximate the CC, and heat removed from the CC via water evaporating from the CC can be determined using a decreasing relative humidity proximate the CC.

Selective catalytic reduction device (SCR) assessment methods include, while communicating exhaust to the SCR, determining a first temperature differential (dT) between a modeled exotherm phase temperature and a measured SCR exotherm outlet exhaust temperature, comparing the first dT to a first threshold, and determining that the SCR performance is suitable if the first dT is below the first threshold, or, if the first dT is above the first threshold, communicating exhaust gas to the SCR during a water endotherm phase, determining a second dT between a modeled endotherm phase temperature and a measured SCR endotherm phase outlet exhaust temperature, comparing the second dT to a second threshold, and determining that the SCR performance is suitable if the second dT is above the second threshold, or determining that the SCR performance is unsuitable if the second dT is below the second threshold. Performance can be SCR reductant storage capacity.

Methods and systems are provided for operating an exhaust oxygen sensor coupled to an exhaust passage of an internal combustion engine in response to detecting water at the sensor. In one example, a method may include indicating water at an exhaust oxygen sensor positioned in an engine exhaust passage based on a sensor parameter of the exhaust oxygen sensor while operating the exhaust oxygen sensor in a variable voltage (VVs) mode where a reference voltage is adjusted from a lower, first voltage to a higher, second voltage; and adjusting one or more of sensor operation and engine operation based on the indicating water.

Methods for monitoring thermal characteristics of oxidation catalyst (OC) catalytic composition(s) (CC) are provided, and comprise communicating exhaust gas to the OC, and determining a temperature change of the CC for the time frame based on a plurality of heat sources including heat imparted to the CC from exhaust gas enthalpy, heat imparted to the CC via oxidation of HC and/or CO in exhaust gas, heat imparted to the CC via water present in the exhaust gas condensing on the CC or heat removed from the CC via water evaporating from the CC, and optionally heat exchanged between the CC and the ambient environment. Heat imparted to the CC via water condensing on the CC can be determined using an increasing relative humidity proximate the CC, and heat removed from the CC via water evaporating from the CC can be determined using a decreasing relative humidity proximate the CC.

Methods and systems are provided for operating an engine exhaust aftertreatment system to increase the efficiency of an exhaust underbody catalyst and reduce engine emissions. In one example, a bypass passage may be coupled to a main exhaust passage and during conditions which may adversely affect functionality of the underbody catalyst, exhaust may be opportunistically routed via the bypass passage avoiding the underbody catalyst. Exhaust heat may be recovered via a heat exchanger coupled to the bypass passage, and the heat may be used for engine heating, and passenger cabin heating.

The invention is directed to a method for determining the state of aging of a catalytic converter (2). The disclosed method functions in a non-contacting manner as resonances formed when the catalytic converter (2) located in a housing is excited with high-frequency electromagnetic waves are analyzed.

A device and method for correcting emissions can include a first sensor that measures a sample of air not containing an exhaust gas, and a second sensor, wherein the exhaust gas enters a settling chamber and a relative humidity of the exhaust gas is measured by the second sensor. A microcomputer can calculate a mass of water vapor in the sample of air measured by the first sensor and in the exhaust gas measured by the second sensor and can determine a dilution factor of the measured exhaust gas. The dilution factor can be used for correcting emissions based on the measurements of the exhaust gas made by the first sensor and the second sensor. The first and second sensors can comprise one or more of, for example, a relative humidity sensor, a dew point sensor, a trace water vapor sensor and/or other types of sensors.

An emission control system, such as an emission control system for a diesel engine, which includes both a NOx sensor and an electrostatic Particulate Matter (ePM) sensor, and uses the signal from the ePM sensor to determine when it is safe to activate and heat up the NOx sensor after engine ignition. This is performed as soon as moisture clears the exhaust, without having to wait any additional time as a safety factor to maximize the reliability of the NOx sensor against damage from water thermal shock. It also allows for a higher degree of application flexibility for a specific engine and aftertreatment combination to be used in a variety of vehicle applications, environmental conditions, and vehicle operating profiles.

Methods and systems are provided for operating an exhaust oxygen sensor coupled to an exhaust passage of an internal combustion engine in response to detecting water at the sensor. In one example, a method may include indicating water at an exhaust oxygen sensor positioned in an engine exhaust passage based on a sensor parameter of the exhaust oxygen sensor while operating the exhaust oxygen sensor in a variable voltage (VVs) mode where a reference voltage is adjusted from a lower, first voltage to a higher, second voltage; and adjusting one or more of sensor operation and engine operation based on the indicating water.