{
  "$type": "site.standard.document",
  "description": "A method and system for controlling the operation of \"lean-burn\" internal combustion engines determines a current rate of vehicle NOx emissions, and determines a threshold value for permissible vehicle NOx emissions based on at least one current value for the intake air-fuel ratio, engine speed…",
  "path": "/patents/1110131",
  "publishedAt": "2001-09-19T00:00:00.000Z",
  "site": "at://did:plc:oql6ds5vnff4ugar6rruliwd/site.standard.publication/3mn3ohu7oxx5w",
  "tags": [
    "F01N3/0842",
    "FORD GLOBAL TECH INC [US]"
  ],
  "textContent": "A method and system for controlling the operation of \"lean-burn\" internal combustion engines determines a current rate of vehicle NOx emissions, and determines a threshold value for permissible vehicle NOx emissions based on at least one current value for the intake air-fuel ratio, engine speed, engine load (e.g., brake torque, manifold air pressure, or throttle position), and/or vehicle speed. A differential NOx emissions rate is calculated as the difference between the current rate and the threshold rate, and the differential rate is accumulated over time to obtain a differential measure representing the amount by which cumulative NOx emissions have fallen below permissible levels therefor. Lean engine operation is disabled when the differential NOx emissions measure exceeds a predetermined excess vehicle NOx emission value. In this manner, vehicle NOx emissions are favourably controlled even when the engine is operated \"off-cycle,\" i.e., under operating conditions falling outside of the FTP driving cycles.",
  "title": "Method and apparatus for controlling lean operation of an internal combustion engine"
}