PUMP GP-PISTON 1559912 - Caterpillar

Illustration 1 is a diagram of the systems main components.
Illustration 1 g01456978
Diagram of the system for the air/fuel ratio controlTo 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".
"Fuel Quality"
"Gas Specific Gravity"
"Fuel Specific Heat Ratio"
"Emissions Feedback Mode Configuration"
"Desired Engine Exhaust NOx Level Setting"
"Air/Fuel Proportional Gain"
"Air/Fuel Integral Gain"Note: Some fuel metering valves utilize the "Gas Specific Gravity" and the "Fuel Specific Heat Ratio" parameters. The fuel metering valve uses this information to help regulate the fuel flow.The air/fuel ratio control has two basic modes of operation:
Open loop
NOX feedbackThe mode of operation is determined by the "Emissions Feedback Mode Configuration" parameter. Cat ET is used to change the mode of operation.Select "Disable" in order to activate the open loop mode.Select "Enable" in order to activate the feedback mode.The modes of operation are explained below.Open Loop
Illustration 2 g01457790
Diagram of the open loop mode (no feedback)Open loop - During operation in this mode, the ECM does not use any feedback for determining the fuel command. The open loop mode is intended to be a temporary mode of operation. The open loop mode allows the engine to operate if the feedback system becomes inoperative. In this mode, the ECM cannot maintain consistent exhaust emissions. Input from an operator that is working with an exhaust analyzer is necessary for maintaining the exhaust emissions.For this mode of operation, the ECM performs several operations in order to determine the fuel command.Volumetric efficiency - The volumetric efficiency of an engine with a four stroke cycle is the relationship between the quantity of the inlet air and the piston displacement. This is the ratio between the charge that actually enters the cylinder and the amount that could enter the cylinder under ideal conditions. To determine the volumetric efficiency, the volume of the engines inlet air is compared to the piston displacement.The ECM uses four factors to calculate the air flow: inlet manifold air temperature, inlet manifold air pressure, engine speed and a map of volumetric efficiency. The engine speed and the calculated engine load are used as references for the map. The corresponding point on the map is used with the other factors in the calculation of the air flow. The ECM assumes that this is the current air flow.The ECM assumes that the current fuel command is the actual fuel flow: the fuel flow is used to calculate the engine load. The ECM uses the engine speed and the calculated engine load as references for a map of the desired air/fuel ratio. The point on the corresponding point on the map determines the desired air/fuel ratio.The ECM uses the calculated air flow and the desired air/fuel ratio to calculate the fuel command. The calculation is in Illustration 3.
Illustration 3 g01024465
The command for the fuel flow is then adjusted with the "Fuel Quality" parameter which is entered into the ECM with Cat