A system, apparatus, and method for controlling an engine system can provide fuel reactivity compensation control for an engine of the engine system. The control can include controlling pilot fuel quantity supplied to an engine based on a pilot fuel offset value; and controlling air-to-fuel ratio (AFR) for the engine based on an AFR control trim value. A NOx error value can be used to generate one of the pilot fuel offset value or the AFR control trim value, and an exhaust temperature error value can be used to generate the other of the pilot fuel offset value or the AFR control trim value.

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.

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).

Various methods and systems are provided for controlling emissions. In one example, a controller is configured to respond to a sensed exhaust oxygen concentration by changing a fuel injection timing to maintain particulate matter (PM) within a range, and then adjusting an exhaust gas recirculation (EGR) amount based on NOx sensor output and based on the change in fuel injection timing.

A spark ignited internal combustion engine is controlled in response to a self-learned TOB reference. The self-learned TOB reference is based on a difference between a learned TOB offset and a desired or target TOB, and a sensed TOB. The learned TOB offset at a given operating condition, such as charge pressure, can be found by interpolating between the learned charge pressure breakpoints in a TOB learning algorithm. The TOB learning algorithm can include using a filtered charge pressure value to indicate the engine load at which the TOB is learned. An index determination is made with a look up table with charge pressure as an input and an array index of learned charge pressure and learned TOB offset as outputs.

System for controlling an engine provided with an exhaust gas post-treatment system of the selective catalysis type, including a closed-loop control of NO.sub.x before the gas post-treatment system, according to the following steps: ⋅ a unit for determining a NO.sub.x setpoint in dependence on the rotational speed and the torque setpoint of the engine, ⋅ a unit for determining a NO value, and ⋅ a cascade control unit which is able to determine a setpoint for admitted oxygen and a correction of the supercharging pressure destined for unit for controlling the air loop of the engine as well as a correction of the injection pressure and a correction of the advance of the main injection in dependence on a NO.sub.x difference, between a NOx emission setpoint or corrected emission setpoint and a determined value of the quantity of NO.sub.x.

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.

Various embodiments include methods for determining the efficiency of an SCR catalytic converter in a system including a nitrogen oxide sensor, and a metering device for a reducing agent arranged in an exhaust-gas duct, and an exhaust recirculation line with a recirculation valve disposed downstream of the SCR catalytic converter and feeding an intake region of the engine. The methods comprise: setting or identifying a quasi-steady-state operating state and an associated recirculation rate; adding a first quantity of reducing agent using the metering device; measuring a resulting first nitrogen oxide value using the sensor; adding a further predefined quantity, different from the first quantity; measuring the resulting nitrogen oxide values using the sensor; and determining the efficiency of the SCR catalytic converter based at least in part on the associated exhaust-gas recirculation rate and the measured nitrogen oxide values.

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.

Various methods and systems are provided for controlling emissions. In one example, a controller is configured to respond to a sensed exhaust oxygen concentration by changing a fuel injection timing to maintain particulate matter (PM) within a range, and then adjusting an exhaust gas recirculation (EGR) amount based on NOx sensor output and based on the change in fuel injection timing.