Abstract: A method is provided for controlling the injection, by a reductant injector in an exhaust system for an internal combustion engine, of reductant for an exhaust aftertreatment unit of the exhaust system, for example a selective catalytic reduction (SCR) unit. The method includes determining a reductant injection debt in dependence on a reductant flow according to at least a first request being higher than a threshold of the reductant flow, and, at least partly in dependence on the reductant injection debt, controlling the reductant injector so as to inject a compensation flow.

Abstract: A method is provided for controlling the injection, by a reductant injector in an exhaust system for an internal combustion engine, of reductant for an exhaust aftertreatment unit of the exhaust system, for example a selective catalytic reduction (SCR) unit. The method includes determining a reductant injection debt in dependence on a reductant flow according to at least a first request being higher than a threshold of the reductant flow, and, at least partly in dependence on the reductant injection debt, controlling the reductant injector so as to inject a compensation flow.

Abstract: In a method for estimating the quality of an urea based reagent in terms of urea concentration, the reagent is injected upstream of a SCR catalyst in an exhaust aftertreatment system. A demanded NOx conversion rate is set substantially lower than a currently estimated maximum NOx conversion rate of the SCR catalyst. An actual NOx conversion rate is monitored for a certain time period. The urea concentration of the reagent is estimated based on comparing the monitored actual NOx conversion and the demanded NOx conversion during the time period. A corresponding system is also disclosed.

Abstract: A method for controlling a reductant buffer level in an exhaust gas after treatment device connectable downstream of an internal combustion engine includes performing a first reductant injection of a first amount upstream the exhaust gas after treatment device, performing a second reductant injection of a second amount upstream the exhaust gas after treatment device, which second amount is different to the first amount, evaluating the NOx conversion resulting from the first and second reductant injections downstream the exhaust gas after treatment device to obtain a first and second result, controlling a further reductant injection in dependence of the first and second results from the first and second NOx conversion evaluations.

Abstract: A method for controlling a reductant buffer level in an exhaust gas after treatment device connectable downstream of an internal combustion engine includes performing a first reductant injection of a first amount upstream the exhaust gas after treatment device, performing a second reductant injection of a second amount upstream the exhaust gas after treatment device, which second amount is different to the first amount, evaluating the NOx conversion resulting from the first and second reductant injections downstream the exhaust gas after treatment device to obtain a first and second result, controlling a further reductant injection in dependence of the first and second results from the first and second NOx conversion evaluations.

Abstract: In a method for estimating the quality of an urea based reagent in terms of urea concentration, the reagent is injected upstream of a SCR catalyst in an exhaust aftertreatment system. A demanded NOx conversion rate is set substantially lower than a currently estimated maximum NOx conversion rate of the SCR catalyst. An actual NOx conversion rate is monitored for a certain time period. The urea concentration of the reagent is estimated based on comparing the monitored actual NOx conversion and the demanded NOx conversion during the time period. A corresponding system is also disclosed.

Abstract: A method for controlling a reductant buffer level in an exhaust gas after treatment device connectable downstream of an internal combustion engine includes performing a first reductant injection of a first amount upstream the exhaust gas after treatment device, performing a second reductant injection of a second amount upstream the exhaust gas after treatment device, which second amount is different to the first amount, evaluating the NOx conversion resulting from the first and second reductant injections downstream the exhaust gas after treatment device to obtain a first and second result, controlling a further reductant injection in dependence of the first and second results from the first and second NOx conversion evaluations.

Abstract: Method for controlling the braking effect during engine braking in an internal combustion engine (10) having an exhaust turbocharger unit (16) with adjustable guide blades for controlling the turbine speed and gas flow. The method includes detection of the engine speed, detection of the adjustment position of the guide blades, measurement either of the charging pressure on the intake side of the engine or the manifold pressure on the exhaust side of the engine, comparison of these data with stored desired values, and adjustment of the guide blades to a desired position which gives a suitable braking effect for the prevailing charging pressure.

Abstract: Method for controlling the braking effect during engine braking in an internal combustion engine (10) having an exhaust turbocharger unit (16) with adjustable guide blades for controlling the turbine speed and gas flow. The method includes detection of the engine speed, detection of the adjustment position of the guide blades, measurement either of the charging pressure on the intake side of the engine or the manifold pressure on the exhaust side of the engine, comparison of these data with stored desired values, and adjustment of the guide blades to a desired position which gives a suitable braking effect for the prevailing charging pressure.