Patent ID: 8745973

Claim:
An engine control system, comprising: a first electronic circuit configured to (i) during a first period, actuate an injector to inject a first amount of reducing agent into exhaust gas produced by an engine, wherein the first period begins when a temperature of the exhaust gas increases above a temperature threshold, and wherein the exhaust gas temperature being greater than the temperature threshold results in regeneration of a particulate matter filter, and (ii) during a second period, actuate the injector to inject a second amount of the reducing agent into the exhaust gas, wherein the second period is subsequent to the first period and begins when the temperature of the exhaust gas falls below the temperature threshold; and a second electronic circuit configured to, during the first period, (i) determine an efficiency of a selective catalytic reduction (SCR) material based on measured amounts of nitrogen oxide (NOx) during the first period and expected NOx amounts, and (ii) determine a dosing offset based on the determined efficiency of the SCR material, wherein the second amount of the reducing agent is based on the dosing offset.