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Product: GENERATOR SET

Model: G3520B GENERATOR SET CWD
Configuration: G3520 Generator Set CWD00001-UP

Testing and Adjusting

G3500B Engines
Media Number -RENR2268-11 Publication Date -01/08/2012 Date Updated -06/06/2017

i05654770

Air/Fuel Ratio Control - Adjust - Oxygen Feedback - Generator Set

Application
SMCS - 1266-025

S/N - 7EZ1-UP

S/N - BGW1-UP

S/N - CEY1-UP

S/N - CFD1-UP

S/N - CME1-UP

S/N - CSC1-UP

S/N - CTK1-UP

S/N - CTW1-UP

S/N - CWD1-UP

S/N - GZP1-UP

S/N - KAD1-UP

S/N - L6H1-UP

S/N - L6J1-UP

S/N - ZBB1-UP

S/N - ZBC1-UP

The air/fuel ratio must be adjusted properly in order to comply with the emissions requirements of the site.
The correct air/fuel ratio also helps ensure stable operation. To adjust the air/fuel ratio, perform the following
procedure.

Table 1
 Tools Needed Qty
391-8170 EMISSIONS ANALYZER TOOL GP - (Bluetooth Module) (1) 1
393-0673 EMISSIONS ANALYZER TOOL GP (1) 1
(1)
Either emissions analyzer may be used.

1. Connect a properly calibrated emissions analyzer to the exhaust stack.

2. Connect the Caterpillar Electronic Technician (ET) to the service tool connector. Refer to Systems
Operation/Testing and Adjusting, "General Information (Electronic Control System)".

3. Use the data from the gas analysis in order to determine the correct settings for the "Fuel Quality" and
for the "Gas Specific Gravity" parameters.

4. Calibrate the oxygen sensor. Refer to the engines Troubleshooting manual for the procedure.

5. Start the engine.

6. Engage the driven equipment.

7. Select "Configuration" from the "Service" drop-down menu. Select "Air Fuel Ratio Tuning" from the
selection menu. Set the "Oxygen Feedback Enabled Status" to "Disabled".

The engine will now operate in open loop mode.

8. Slowly ramp the load up to 100 percent or to the normal load for the site.

Note: Watch the "Fuel Valve Position" parameter and the "Throttle Position" parameter. If either the
"Fuel Valve Position" or the "Throttle Position" reaches 80 percent, reduce the load at least 5 percent.
Perform the following steps before proceeding to add load.

a. If the "Fuel Valve Position" has reached 100 percent, there is a problem with the fuel supply.
Consider the following conditions as potential problems:

◾ Verify that the values of the "Fuel Quality", the "Gas Specific Gravity", and the "Fuel
Specific Heat Ratio" parameters are correct.

◾ The fuel pressure to the fuel control valve may be too low.

◾ The Low Heat Value (LHV) of the fuel may be too low. If the LHV is too low, the fuel
system will not be able to supply enough fuel for the rating.

b. Adjust the exhaust bypass valve. Refer to Systems Operation, Testing and Adjusting, "Exhaust
Bypass Valve (Adjust)".

9. Select "Configuration" from the "Service" drop-down menu. Adjust the "Fuel Quality" parameter in
order to obtain the values of emissions that are required at the site.

◦ To make the air/fuel ratio leaner, increase the "Fuel Quality" parameter.

◦ To make the air/fuel ratio richer, decrease the "Fuel Quality" parameter.

When you adjust the "Fuel Quality" parameter, make small changes in the value of the parameter. Wait
until the system stabilizes. Check the emissions again. Repeat the process until the desired level of
emissions level is achieved.

Use the emissions analyzer in order to verify that the values of emissions meet the requirements of the
site.
 10. Once the correct emissions are obtained, review the "Actual Oxygen" and "Desired Oxygen" values.
The engine must still be in the open loop mode.

If the "Actual Oxygen" is higher than the "Desired Oxygen", use the following equation. This equation
is used in order to determine the new value for the "Desired Oxygen at Full Load" parameter:

Table 2
Equation for the Calculation of a New Value for the "Desired Oxygen at Full Load"
Parameter
N=(A-D)+C
N is the new "Desired Oxygen at Full Load" value.
A is the "Actual Oxygen" value.
D is the "Desired Oxygen" value.
C is the current "Desired Oxygen at Full Load" value.

If the "Actual Oxygen" is lower than the "Desired Oxygen", use the following equation in order to
determine the new value for the "Desired Oxygen at Full Load" parameter:

Table 3
Equation for the Calculation of a New Value for the "Desired Oxygen at Full Load"
Parameter
N=C-(D-A)
N is the new "Desired Oxygen at Full Load" value.
C is the current "Desired Oxygen at Full Load" value.
D is the "Desired Oxygen" value.
A is the "Actual Oxygen" value.

11. Enter the new value for the "Desired Oxygen at Full Load" parameter with Cat ET.

12. Ensure that the "Desired Oxygen" and the "Actual Oxygen" parameters are the same value.

13. Select "Configuration" from the "Service" drop-down menu. Select "Air Fuel Ratio Tuning" from the
selection menu. Set the "Oxygen Feedback Enabled Status" to "Enabled".

The engine is now operating in closed loop mode.

14. The engines operation should not change in closed loop mode. If the engine operation changes, change
the "Oxygen Feedback Enabled Status" to "Disabled" and perform the necessary troubleshooting steps.

Note: When the engine is running in closed loop mode, the Fuel Correction Factor (FCF) will change.
The FCF will change in order to compensate for the fuel quality and for the ambient conditions.

15. Check the emissions level. Verify that the emissions meet the requirements of the site.

16. Record the data from all of the status groups on Cat ET. Save the data for future reference.

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