CORE 7N4987 - Caterpillar

The response of the throttle actuator can be adjusted with the Caterpillar Electronic Technician (ET). Use Cat ET to change these two parameters:
"Governor (Proportional) Gain Percentage"
"Governor (Integral) Stability Percentage"The default values should be sufficient for initial start-up. However, the values may not provide optimum performance.These adjustments are provided in order to obtain optimum responses to changes in the load and in the speed. The adjustments also provide stability during steady state operation.If you have a problem with instability, always investigate other causes before you adjust the governor. For example, diagnostic codes and unstable gas pressure can cause instability.To change the parameters, use the "Real Time Graphing" feature on the "Information" drop-down menu of Cat ET. The graph provides the best method for observing the effects of your adjustments.For details on these parameters, refer to Systems Operation/Testing and Adjusting, "Electronic Control System Parameters". After you make adjustments, always test the stability by interrupting the engine speed and/or load. Operate the engine through the entire range of speeds and of loads in order to ensure stability.Note: Adjustment of the "Governor (Proportional) Gain Percentage" directly affects the speed of the throttle actuator when there is a difference between the actual engine speed and the desired engine speed. An excessive increase of this parameter may amplify instability.To set the "Governor (Proportional) Gain Percentage", increase the value until the actuator becomes unstable. Slowly reduce the value in order to stabilize the actuator. Observe that the engine operates properly with little overshoot or undershoot.The adjustment of "Governor (Integral) Stability Percentage" dampens the actuator's response to changes in load and in speed. Increasing this value provides less damping. Decreasing the value provides more damping. To reduce overshoot, decrease the value. To reduce undershoot, increase the value.Note: An increase of the "Governor (Integral) Stability Percentage" may require a decrease of the "Governor (Proportional) Gain Percentage" in order to maintain a stable operation.Illustration 1 shows some typical curves for transient responses.
Illustration 1 g01017530
(Y) Engine speed
(X) Time
(1) The "Governor (Proportional) Gain Percentage" is too high and the "Governor (Integral) Stability Percentage" is too low. There is a large overshoot on start-up and there are secondary overshoots on transient loads.
(2) The "Governor (Proportional) Gain Percentage" is slightly high and the "Governor (Integral) Stability Percentage" is slightly low. There is a slight overshoot on start-up but the response to transient loads is optimum.
(3) The "Governor (Proportional) Gain Percentage" is slightly low and the "Governor (Integral) Stability Percentage" is slightly high. There is optimum performance on start-up but slow response for transient loads.
(4) The "Governor (Proportional) Gain Percentage" is too low and the "Governor (Integral) Stability Percentage" is too high. The response for transient loads is too slow.
(5) The response to transient loads is adjusted for optimum performance. Governor Type
Use Cat ET to select the "Governor Type Setting" configuration parameter. There are two sets of responses for the throttle actuator. The "Governor Type Setting" parameter can be set to "Isochronous" or to "Droop". This setting is dependent upon the application of the