Open Loop Position Variation

An additional function of the MCU is to correct for a change in ambient conditions (altitude). During closed loop operation, the MCU stores the number of steps and direction that the metering pins are driven to correct oxygen content of exhaust gases. If the movements are consistently to the same position, the MCU will vary all open loop operation preset metering pin positions a corresponding amount. This function allows the open loop air/fuel mixture ratios to be adjusted to the existing ambient condition during each uninterrupted use of the system to optimize emission control and engine performance.