HOSE AS 4999460 - Caterpillar

The desired air/fuel ratio is based on maps that are stored in the ECM. The maps are specific for different applications, for engine speeds, and for engine loads.The engine load is calculated from the fuel flow. The load calculation starts at 500 rpm and the load reads zero below 500 rpm.Note: The calculated engine load varies. Several variables affect the calculated engine load, including timing, settings for emissions, fuel quality, and specific gravity of the fuel.G3606, G3608, and G3612The volume of fuel that is consumed by combustion is calculated by the TecJet measuring the following conditions:
Fuel inlet pressure
Fuel temperature
TecJet differential pressureG3616The volume of fuel that is consumed by combustion is calculated by measuring the following conditions:
Pressure differential between the fuel manifold and the inlet air manifold
Temperature of the fuel to the cylinder
Engine rpmThe system has three modes of operation for the air/fuel ratio:
Start-up mode (fixed actuator positions)
NOx feedback disabled mode (open loop and prechamber calibration operates in this mode)
NOx feedback enabled mode (closed loop NOx control)The relationship of the modes of operation to the speed and load and the transitions between the modes are represented in Illustrations 3 and 4.The modes of operation are explained in more detail below.
Illustration 3 g03807798
G3606, G3608, and G3612
Illustration 4 g03808256
G3616
The NOx feedback enabled mode and air system initialization thresholds have high and low speed (and high/low load for NOx feedback) values. If the high threshold is crossed, they remain active even if speed drops below the high threshold, until the low threshold is crossed. The area between the low and high thresholds is called the hysteresis band, and it prevents the controls from switching on and off rapidly during small engine speed/load fluctuations. The hysteresis band on the A4 has a wider range than on the A3.
The air system becomes active at 500 rpm for the G3606, G3608, and G3612, and the air system becomes active at 700 rpm for the G3616.
The green region in Illustration 3 shows the NOx feedback/No feedback hysteresis band on the G3606, G3608, and G3612. The brown region in Illustration 4 hysteresis band for all 3 modes on G3616.
The upper left hashed region is based on the recommended 30 percent maximum startup load.
In the "Start-up" mode, the choke and wastegate actuator positions are fixed. The choke position is set to value in Cat ET and the wastegate position is fixed by the software. The start-up wastegate position cannot be changed like in the A3 software.
In the NOx feedback disabled mode (open loop), air/fuel ratio is controlled to desired value in map. This is a function of the IMAT, speed, and load.
In the NOx feedback enabled mode, air/fuel ratio is trimmed until the NOx sensor reading matches the set point in Cat ET via the fuel correction factor.
If the engine enters the hysteresis band below 40 percent load, the desired NOx target is scaled up by 10 ppm per 10 percent load. For example, if the Cat ET set point is 50 ppm, at 30 percent load the controller will