| abstract |
A memory type fuel control system and method of operating a motor vehicle internal combustion engine having a three-way catalytic converter. A fuel flow control system provides a fuel supply rate near the air/fuel ratio at which the catalytic converter has maximum three-way conversion efficiency. The fuel supply rate so determined is trimmed by a trim factor recalled from memory, the authority of this trim factor being sufficient to compensate for engine and controller variations with time, manufacturing tolerances, etc. In the preferred form, the trim factor is stored in memory at an address determined by the same engine operating conditions that control the fuel supply. The engine exhaust gas oxidizing/reducing conditions are sensed by exhaust gas sensors. In the preferred form, a closed loop controller is responsive to the deviation of the sensed oxidizing/reducing conditions from the condition at which the catalytic converter has maximum three-way conversion efficiency to adjust the trimmed fuel supply rate in a sense to produce the oxidizing/reducing condition at which the maximum conversion efficiency is obtained. A sampling circuit recurrently samples and momentarily stores the engine operating conditions, such as engine load and speed conditions, in a short term memory to form a history of those conditions extending back at least by the amount of the engine transport delay time. At a later time, the exhaust gas oxidizing/reducing conditions sensed by the exhaust gas sensor is sampled, the engine operating conditions that produced the sampled exhaust gas condition are recalled from the short term memory, a new trimming value is determined for the recalled vehicle conditions which more closely produce a desired oxidizing/reducing condition, and such value is inserted in the main memory at the address determined by the recalled conditions. Such trim factor is then available for recall and use as the trimming factor when the engine is next operated under such conditions. |