HUB 8P3133 - Caterpillar

Adjusting the position of the inlet manifold choke plate can significantly improve the stability of the engine during low speed and/or low load engine operating conditions. Also, the load acceptance capability of the engine can be affected depending on the position of the choke plate at low engine load.In generator set applications, idle stability is critical for synchronization of the generator set with the electrical grid. Follow the chart for the Recommended Inlet Manifold Pressure, with no load on the engine.
Table 1
Recommended Inlet Manifold Pressure    
Engine RPM     Inlet Manifold Pressure (1)    
900    
40 5 kPaa (5.8 .7 psia)    
1000    
50 5 kPaa (7.3 .7 psia)    
( 1 ) kPaa is kilopascal measured in absolute pressure.These recommended values are provided for reference only. Parasitic loads affect the required inlet manifold pressure. The engine choke trim can and should be adjusted to a manifold pressure level that provides the optimum engine stability and the load acceptance capability for the specific application of the engine.Electronic Choke Trim Procedure
Set the engine operating condition to the rated speed and no load (or minimum load possible).
Connect the DDT to the Engine Supervisory System (ESS). Display the DDT screen "number 33" by pressing the "SELECT MODE" key in order to display the "CSP MENU" (customer selectable parameters) screen "number 03". Then press the "SELECT FUNC" key to display screen "number 33". Or simply enter the "number 33" and then press the "ENTER" key.Screen "number 33" on the DDT will display the following:"CHOKE TRIM""00 40/0900 33<"The numbers on the second line of the display are: The choke trim "OFFSET" number which indicates the amount of offset that has been entered through the "ALT1" and the "ALT2" keys. The amount of the choke trim offset "00" represents the factory default setting. "40/0900" represents the Inlet Manifold Pressure (kPaa)/Engine speed (rpm).Note: kPaa is kilopascal measured in absolute pressure.
On the DDT screen "number 33", when the "ALT1" or "ALT2" keys are pressed, a command signal is sent to the choke actuator in order to change the position of the choke plate.To raise the inlet manifold pressure, press the "ALT2" key. (The offset number on the DDT screen will decrease by one every time the "ALT2" key is pressed.)To lower the inlet manifold pressure, press the "ALT1" key. (The offset number on the DDT screen will increase by one every time the "ALT1" key is pressed.)This process should be done slowly. Pause after every adjustment in order to allow the engine to respond to the change in the inlet manifold pressure.Monitor the following:
inlet manifold pressure
stability of the engine rpm
position of choke actuator
position of wastegate actuator
individual cylinder combustion burn times
individual cylinder exhaust port temperaturesTo monitor individual cylinder misfire during the choke trim process, alternate between the choke trim mode and