CABLE AS 1918726 - Caterpillar

The Electronic Control Module (ECM) provides control of the air/fuel mixture for maximum performance and for efficiency at low emission levels. The system consists of the following components: maps in the ECM, output drivers in the ECM, sensors and customer's input via the Caterpillar Electronic Technician (ET). The ECM compensates for changes in the BTU of the fuel in order to maintain desired emission levels. Illustration 1 is a diagram of the system's main components.
Illustration 1 g01389952
Diagram of the system for the air/fuel ratio control
To accurately control the air/fuel ratio, the ECM depends on the following parameters that are programmed via the "Configuration" screen of Cat ET. For details on these parameters, refer to Systems Operation/Testing and Adjusting, "Electronic Control System Parameters".
"Emissions Feedback Mode configuration"
"Desired Engine Exhaust NOx Level Setting"
"Air/Fuel Proportional Gain"
"Air/Fuel Integral Gain"
"Desired Fuel Valve Position"Air/Fuel Ratio Control
The system consists of an electronic fuel metering valve, output drivers in the ECM, and maps in the ECM. The ECM compensates for changes in the BTU of the fuel in order to maintain desired emission levels.The air/fuel ratio is controlled whenever the air/fuel ratio control is enabled via the "Emissions Feedback Mode" configuration.The following steps describe the basic operation:
The ECM uses the following factors in order to determine the desired fuel flow rate:
Desired engine speed
Actual engine speed
Calculated engine load
The amount of NOX in the exhaustThe ECM monitors a sensor in order to determine the amount of NOX in the exhaust.
The ECM determines the rate of fuel flow that is required in order to achieve the desired level of NOX in the exhaust. The ECM develops a command signal for the fuel flow. The signal is sent to the electronic fuel metering valve via the CAN data link.