G3520B Industrial Engines Caterpillar

Electronic Control System Parameters

Usage:

Table 1 is a list of the parameters that can be configured for G3520B Industrial Engines. The parameters are programmed into the Electronic Control Module (ECM) via the Caterpillar Electronic Technician (ET). The values of the parameters can be viewed on the "Configuration" screen of Cat ET.

Show/hide table

Table 1
Configuration Parameters for G3520B Industrial Engines
Parameter
Timing Control
First Desired Timing
Second Desired Timing
Desired Engine Timing Offsett
Air/Fuel Ratio Control
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
Speed Control
Low Idle Speed
Minimum Engine High Idle Speed
Maximum Engine High Idle Speed
Engine Acceleration Rate
Desired Speed Input Configuration
Governor Type Setting
Engine Operation
Engine Speed Droop
Governor Gain Factor
Governor Stability Factor
Governor Compensation Factor
Auxiliary Proportional Governor Gain 1
Auxiliary Integral Governor Gain 1
Auxiliary Derivative Governor Gain 1
Start/Stop Control
Driven Equipment Delay Time
Crank Terminate RPM
Engine Purge Cycle Time
Cooldown Duration
Cycle Crank Time
Engine Overcrank Time
Engine Speed Drop Time
Engine Prelube
Engine Prelube Time Out Period
Engine Postlube Duration
Monitoring and Protection
High Inlet Air Temp Engine Load Set Point
Module Information
Engine Serial Number
Equipment ID
Customer Password #1
Customer Password #2
Total Tattletale

Timing Control

The timing parameters allow the customer to program the timing electronically of the ignition spark to meet the needs for specific applications and installations. The desired timing value can be changed while the engine is running or while the engine is stopped.

Note: The actual ignition timing at a given instance may vary from the desired timing value. This variance is due to variations in the engine speed or in the detonation.

"First Desired Timing"

The "First Desired Timing" is determined with the methane number of the primary fuel that is used. Use the Engine Performance Sheet, "Fuel Usage Guide". The ECM selects the "First Desired Timing" when the timing select switch creates an open circuit for terminal J1-20 at the master ECM.

"Second Desired Timing"

The "Second Desired Timing" is determined with the methane number of the alternate fuel that is used and the Engine Performance Sheet, "Fuel Usage Guide". The ECM selects the "Second Desired Timing" when the timing select switch creates a short circuit to ground for terminal J1-20 at the master ECM.

If an alternate fuel is not used, enter the same timing value for the "Second Desired Timing" parameter that is entered in the "First Desired Timing" parameter.

"Desired Engine Timing Offset"

The feature provides the offset of engine ignition timing to compensate for timing errors. The errors are due to resistances in the electrical circuitry and stackup of mechanical tolerances.

This parameter provides a manual method that will allow additional timing adjustment to be performed after calibration of the speed/timing sensor. Perform a negative adjustment to this parameter for retardation of the engine timing. Perform a positive adjustment to this parameter in order to advance the engine timing. Only perform an adjustment to this parameter if engine operating indicators and measured data indicate that an adjustment is required.

Air/Fuel Ratio Control

Before the initial start-up, a current gas analysis is required. Periodic gas analyses are also recommended. Use the Caterpillar Software, LEKQ6378, "Methane Number Program" in order to calculate the parameters for air/fuel ratio control for Caterpillar Gas Engines. The results are programmed into the ECM.

Note: Use the Caterpillar Software, LEKQ6378, "Methane Number Program". The improper programming of the air/fuel ratio control can result in damage to the engine.

"Fuel Quality"

This parameter is the fuel Low Heat Value (LHV). The air/fuel ratio control of the ECM will compensate for some inaccuracy in this setting. The ECM assumes a corrected value that is multiplied by the "Fuel Correction Factor". The status of the parameter can be viewed with Cat ET.

The "Fuel Quality" parameter can be used to change the air/fuel ratio when the engine is operating in the open loop mode. To richen the air/fuel mixture, reduce the value. The calculation will compensate for the reduced LHV by increasing the fuel flow. To lean the air/fuel mixture, increase the value. The calculation will compensate for the increased LHV by reducing the fuel flow.

"Gas Specific Gravity"

This parameter is the fuel-specific gravity in relation to the specific gravity of air. The ECM does not use this information. The ECM provides the information to the fuel metering valve via the CAN data link. Some fuel metering valves require an input for the "Gas Specific Gravity" in order to precisely meter the fuel flow.

"Fuel Specific Heat Ratio"

This parameter is a ratio of the fuel-specific heat at a constant pressure and at a constant volume. The ratio is also known as "k". The ratio is related to the expansion of the gas across the fuel metering valve. The ECM does not use this information. The ECM provides the information to the fuel metering valve via the CAN data link. Some fuel metering valves require an input for the "Fuel Specific Heat Ratio" in order to precisely meter the fuel flow.

"Emissions Feedback Mode Configuration"

The "Emissions Feedback Mode Configuration" can be set to "NOx Feedback" or to "Feedback Disabled". This feature allows the feedback mode to be disabled in order to troubleshoot the engine. The disabling of this feature can determine whether the air/fuel ratio control is the cause of instability of the engine.

If the signal from the NO_X sensor is not available, the control system does not have information necessary for maintaining consistent exhaust emissions.

If there is a problem with the NO_X sensor, this parameter can be set to "Feedback Disabled". "Feedback Disabled" allows the engine to run in the open loop mode until a new sensor is obtained. During operation in this mode, an emissions analyzer must be used to verify the emissions level. The "Fuel Quality" parameter is adjusted in order to adjust the air/fuel mixture.

When the "Emissions Feedback Mode Configuration" is set to "NOx Feedback", adjustment of the "Fuel Quality" parameter does not affect the air/fuel ratio. Do not adjust the "Fuel Quality" parameter when the "Emissions Feedback Mode configuration" is set to "NOx Feedback".

Note: Do not operate an engine that is unattended in the open loop mode if the fuel has an LHV that is changing. The engine risks a shutdown due to lean misfire or to detonation.

"Desired Engine Exhaust NOx Level Setting"

The ECM contains a control map for the NO_X emissions that is programmed at the factory. The "Desired Engine Exhaust NOx Level Setting" parameter is used to trim this control map when the engine is in "NOx Feedback" mode. If the measured NO_X emissions are not the required value, decrease the "Desired Engine Exhaust NOx Level Setting" parameter. The decrease will make the fuel mixture lean. Increase the "Desired Engine Exhaust NOx Level Setting" parameter in order to richen the fuel mixture. The engine must run at normal operating temperature. The engine speed set to a minimum of high idle. The engine load set to a minimum of 50 percent.

"Air/Fuel Proportional Gain"

The "Air/Fuel Proportional Gain" determines speed of the fuel metering valve response. The gain makes adjustments for the difference between actual air/fuel ratio and desired air/fuel ratio.

The factory default setting is 0. This value should not require adjustment. If problems occur, this parameter is one of the last parameters that should be adjusted. Adjustment of the parameter toward negative values reduces the speed of the fuel metering valve response. Positive values increase the speed of the fuel metering valve response.

"Air/Fuel Integral Gain"

The "Air/Fuel Integral Gain" determines the response of the fuel metering valve to the error that is accumulated over time for the air/fuel ratio.

The factory default setting is 0. This value should not require adjustment. If problems occur, this parameter is one of the last parameters that should be adjusted. Adjustment of the parameter toward negative values reduces the response of the valve. Positive values increase the response of the valve.

Speed Control

"Low Idle Speed"

Program this parameter to the desired low idle rpm.

"Minimum High Idle Speed"

Program this parameter to the desired minimum high idle rpm. The actual high idle speed is regulated by the desired speed input. The regulation is linear in proportion to the input. An input of 0 percent results in the minimum high idle rpm and an input of 100 percent results in the maximum high idle rpm.

The "Minimum High Idle Speed" and the "Maximum High Idle Speed" determine the slope of the desired speed input.

"Maximum High Idle Speed"

Program this parameter to the desired maximum high idle rpm. The actual high idle speed is regulated by the desired speed input. The regulation is linear in proportion to the input. An input of 0 percent results in the minimum high idle rpm and an input of 100 percent results in the maximum high idle rpm.

"Engine Acceleration Rate"

This parameter controls the rate for engine response to a change in the desired engine speed. For example, the engine can be programmed to accelerate at a rate of 50 rpm per second when the "Idle/Rated" switch is turned to the "Rated" position.

This parameter is also used for the engine rate of deceleration.

"Desired Speed Input Configuration"

This parameter determines the signal input to the ECM for control of the desired speed for the engine. The signal can be either 0 to 5 VDC or 4 to 20 mA.

Note: The ECM is not configured to accept a pulse width modulated signal (PWM) for input of the desired engine speed. If you try to select a PWM, the ECM will reject the selection. Cat ET will generate an error if this parameter is selected.

"Governor Type Setting"

The "Governor Type Setting" parameter can be set to "Isochronous" or to "Droop". This setting is dependent upon the application of the engine.

"Engine Speed Droop"

This programmable parameter allows precise control of the engine speed droop. The "Governor Type Setting" parameter must be set to "Droop" in order for this parameter to be active.

Governor Gain Settings

This parameter is used in determining the engine rate of response to an engine load. Refer to Testing and Adjusting, "Engine Governing - Adjust" for the adjustment procedure for the governor.

Governor Stability Factor

The adjustment of "Governor Stability Factor" dampens the actuator response to changes in the engine load and speed. Increasing this value provides less damping. Decreasing the value provides more damping. To reduce governor overshoot, decrease the value. For reduction in undershoot of the governor, increase the value. Refer to Testing and Adjusting, "Engine Governing - Adjust" for the adjustment procedure for the governor.

Governor Compensation Factor

This parameter is used to adjust the time delay between the control signal and the movement of the actuator. If the compensation is too low, the engine speed will slowly hunt. If the compensation is too high, the engine speed will rapidly fluctuate. Refer to Testing and Adjusting, "Engine Governing - Adjust" for the adjustment procedure for the governor.

"Auxiliary Proportional Governor Gain 1"

This parameter is based on a proportional multiplier. The "Auxiliary Proportional Governor Gain 1" determines the speed of the throttle actuator response. This gain adjusts for the difference between actual speed and desired speed. Increasing this value provides a faster response to the difference between actual speed and desired speed.

"Auxiliary Integral Governor Gain 1"

This parameter is based on an integral multiplier. The "Auxiliary Integral Governor Gain 1" controls the speed for elimination of the error in the difference between the actual speed and the desired speed. Increasing this value provides less damping.

"Auxiliary Derivative Governor Gain 1"

This parameter is based on a derivative multiplier. The "Auxiliary Derivative Governor Gain 1" is used to adjust for the time delay between the control signal and the movement of the throttle actuator. If this value is too low, the engine speed will slowly hunt. If this value is too high, the engine speed will rapidly fluctuate.

Start/Stop Control Parameters

"Driven Equipment Delay Time"

The ECM accepts an input from the driven equipment that indicates when the equipment is ready for operation. When the input circuit is grounded, the driven equipment is ready. The ECM will not start the engine until this ECM input is grounded.

The ECM can be programmed to wait for a certain time after receiving a start command before starting the engine. This parameter allows the driven equipment to get ready for operation.

When the ECM receives a start command, the ECM will wait for the amount of time that is programmed into the "Driven Equipment Delay Time". If the "Driven Equipment Delay Time" elapses and the input circuit is not grounded, an event code is activated. The engine will not start.

If the "Driven Equipment Delay Time" is programmed to "0", the delay is disabled.

"Crank Terminate Speed"

The ECM disengages the starting motor when the engine speed exceeds the programmed "Crank Terminate Speed". This parameter is preset at the factory and this value should be sufficient for all applications.

"Engine Purge Cycle Time"

The "Engine Purge Cycle Time" is the duration of time for the engine to crank without fuel or spark during the crank cycle. The "Engine Purge Cycle Time" allows any unburned fuel to exit through the exhaust before the fuel and the ignition are enabled.

"Cooldown Duration"

When the ECM receives a stop request, the engine will continue to run in the "Cooldown Mode" for the programmed cooldown period. The cooldown mode is exited early if a request for an emergency stop is received by the ECM. If the "Cooldown Duration" is programmed to zero, the engine will immediately shut down when the ECM receives a stop request.

"Cycle Crank Time"

The "Cycle Crank Time" is the amount of time for activation of the starting motor and of the gas shutoff valve during start-up. If the engine does not start within the specified time, the attempt to start is suspended for a rest cycle. The cycle is also equal to the "Cycle Crank Time".

"Engine Overcrank Time"

The "Engine Overcrank Time" determines the length of time for the ECM to attempt to start the engine. An event is generated if the engine does not start within this time.

"Engine Speed Drop Time"

This parameter is activated when the ECM receives the signal for stopping the engine. This input ensures the shutdown in case the Gas Shutoff Valve (GSOV) fails to close.

After the cooldown period has elapsed, the ECM removes power from the electrical circuit for the GSOV. The fuel is shut off from the engine. The ignition continues until the engine speed drops below 40 rpm. If the engine rpm does not drop at least 100 rpm within the programmed drop time, the ECM terminates the ignition. The ECM issues an emergency stop.

"Engine Prelube"

Engine prelube applies lubricating oil to the bearings before the engine is cranked. The postlube cycle lubricates the turbocharger turbines after the engine shuts down.

The "Engine Prelube" parameter must be enabled in order for the engine prelube to operate.

"Engine Prelube Time Out Period"

This parameter is used by the ECM to protect the engine prelube pump. When the engine mode switch is changed from the STOP/RESET position to the START position, the prelube pump is energized by the ECM. A prelube pump pressure switch is used to detect oil pressure in the engine lubrication system. If oil pressure is not detected within the "Engine Prelube Time Out Period", the prelube cycle is terminated and an event code is generated.

"Engine Postlube Duration"

Once in the postlube cycle, the system runs the prelube pump for a programmable time.

The "Engine Prelube" parameter must be enabled and the "Engine Postlube Duration" parameter must be configured in order for the engine postlube to be enabled.

Monitoring and Protection

"High Inlet Air Temp Engine Load Setpoint"

The programmable setpoint is a value that separates low engine load from high engine load for events that are activated by high inlet air temperature. A status parameter in Cat ET displays the "Engine Load Factor". If the load factor is less than the setpoint and inlet air temperature reaches the trip point, an event code is activated. The code activated is High Inlet Air Temperature at Low Engine Load. If the load factor is greater than the setpoint and the inlet air temperature reaches the trip point, an event code is activated. The code activated is High Inlet Air Temperature at High Engine Load.

Information for the ECM

"Engine Serial Number"

The engine serial number is programmed into the ECM at the factory. The number is stamped on the engine Information Plate.

"Equipment ID"

The customer can assign an "Equipment ID" for identification.

Customer Passwords

Two customer passwords can be entered. The passwords are used to protect certain configuration parameters from unauthorized changes.

Note: Factory level security passwords are required for clearing certain logged events and for changing certain programmable parameters. Because of the passwords, only authorized personnel can change some of the programmable items in the ECM. When the correct passwords are entered, the changes are programmed into the ECM.