An air-fuel ratio control device sets a target air-fuel ratio and performs an air-fuel ratio control based on the target air-fuel ratio for an engine of a spark ignition type. The air-fuel ratio control device includes a lean combustion determination unit that determines whether a lean combustion is performed in the engine at the target air-fuel ratio, the target air-fuel ratio being set leaner than the theoretical air-fuel ratio; a target NOx setting unit that sets a target NOx concentration according to an operation state of the engine; an acquisition unit that acquires an actual NOx concentration detected by using a NOx concentration detection unit in an exhaust passage of the engine; and a correction unit that corrects the target air-fuel ratio based on the target NOx concentration and the actual NOx concentration when determination is made that lean combustion is performed.

The invention relates to a control method that allows the mean quantity of nitrogen oxides per kilometer covered emitted by a vehicle fitted with an internal combustion engine associated with a post-treatment system to be kept below a predefined fixed threshold, for any journey made by the vehicle. The mean quantity emitted over a fixed elementary distance that has just been covered by the vehicle is calculated iteratively, together with a long-term conformity factor which is equal to the mean quantity emitted over the entire distance covered since the start of the journey. When it is found that the long-term conformity factor is above the threshold, the engine and/or the post-treatment system is regulated in such a way as to obtain, over the next fixed elementary distance, a mean quantity of nitrogen oxides per kilometer that is lower than the threshold value FC, for example equal to 90% of the threshold, whatever the engine operating point. Thus, the long-term conformity factor converges towards the threshold.

Various embodiments include a method for operating an internal combustion engine with a three-way catalytic converter with lambda control, comprising: monitoring a NO.sub.x sensor for a lambda value downstream of the converter; setting a threshold value determining a lambda setpoint value upstream of the converter using the difference between the setpoint value of the electrical signal and the measured electrical signal if the signal is below the threshold; if above the threshold value, determining the lambda setpoint value upstream of the converter using the difference between a NH.sub.3 setpoint value of the NO.sub.x sensor and the measured NH.sub.3 signal of the NO.sub.x sensor; and if the measured NH.sub.3 concentration is higher than the NH.sub.3 setpoint value, increasing the lambda setpoint value upstream of the converter and, if the measured NH.sub.3 concentration is lower than the NH.sub.3 setpoint value, reducing the lambda setpoint value upstream of the converter.

A multi-cylinder opposed piston engine (100) can include one or more sensors, such as oxygen or nox sensors (132, 134, 136, 138, 142), for each cylinder (103) of the multi-cylinder opposed piston engine (100). The sensors (132, 134, 136, 138, 142) are in communication with an engine control unit (102) that can receive measurements and other data from the sensors. In one example, each cylinder (103) includes one or more sensors (132, 134) located adjacent to exhaust ports (144) of each individual cylinder (103). In another example, each cylinder (103) includes one or more sensors (136, 138) located in an exhaust passageway (146) of each individual cylinder (103). In some examples, the multi-cylinder opposed piston engine (100) can include multiple crankshafts (114, 116). For example, the multi-cylinder opposed piston engine (100) can include two crankshafts (114, 116), where each crankshaft (114, 116) engages, either directly or indirectly, one of two opposed pistons (104, 106) of a cylinder (103). In one example, each crankshaft (114, 116) includes one or more sensors, such as a torque sensor (120, 122), a speed sensor (124, 126), or a noise, vibration, and harshness (NVH) sensor (150, 152).

It is to determine whether a temperature rise condition of a first cell or a second cell is satisfied based on whether a first parameter has exceeded a predetermined first threshold or a second parameter has exceeded a predetermined second threshold. After satisfaction of the temperature rise condition, it is to determine that an exhaust gas sensor is in an active state upon determination that a corresponding time condition is satisfied.

Various embodiments include a diesel engine comprising: an exhaust gas line; a diesel particulate filter arranged in the exhaust gas line; a first NO sensor arranged in the exhaust gas line upstream of the diesel particulate filter; and a second NO sensor arranged in the exhaust gas line downstream of the diesel particulate filter.

Methods and systems are provided for probabilistic on-board diagnostics. In one example, a method may include calculating a probabilistic metric for a sample of a measured operating condition of a vehicle system component, averaging a plurality of probabilistic metrics including the probabilistic metric for a plurality of samples including the sample, and determining whether the vehicle system component is degraded based on the averaged plurality of probabilistic metrics. In this way, the functionality of a vehicle system component may be continuously monitored without regard for specific diagnostic entry conditions.

Systems, apparatuses, and methods include an upstream exhaust analysis circuit structured to determine a characteristic of an exhaust gas stream entering a nitrous oxide (NOx) storage catalyst; a prediction circuit structured to predict a downstream NOx concentration of an exhaust gas stream exiting the NOx storage catalyst based on a model of a NOx storage capacity or a dynamic response of the NOx storage catalyst; a downstream exhaust analysis circuit structured to determine a downstream NOx concentration of the exhaust gas stream exiting the NOx storage catalyst; and a comparison circuit structured to compare the predicted downstream NOx concentration to the determined downstream NOx concentration, and determine a health of the NOx storage catalyst based on the comparison.

The present invention is an on-board vehicle emissions measurement system. The system comprises at least one sensor (CAP) downstream from the aftertreatment system, and optionally a sensor plugged into the vehicle diagnostics port, and a computer (SIN) including models (MOD VEH, MOD MOD, MOD POT). According to the invention, emissions determination is based on the signal from sensor (CAP) and on models (MOD VEH, MOD MOT, MOD POT).

An exhaust gas after-treatment system for an internal combustion engine includes a selective catalyst reduction on filter (SCRF) exhaust gas after-treatment device in communication with exhaust gases from the internal combustion engine and having treated exhaust gas output. An oxides of nitrogen (NOx) sensor is coupled to treated exhaust gases and has a NOx sensor output signal that is NOx and ammonia (NH.sub.3) cross-sensitive. A closed loop observer (CLO) is operatively coupled to receive the NOx sensor output signal and provides a NOx concentration signal to an electronic control unit operatively associated with the exhaust gas after-treatment system and the internal combustion engine. CLO output at least includes an exhaust gas NOx concentration estimate and the ECU is arranged to be operable upon the NOx concentration estimate to control exhaust gas after-treatment system and internal combustion engine to effect an overall reduction in actual NOx concentration with the exhaust gases.