Note: An emissions analyzer that measures NO and NO2 separately must be used in order to check and to adjust the air/fuel ratio control. The accuracy of the emissions analyzer must be within 10 percent of a standard at the desired engine NO X emissions level. Calibrate the emissions analyzer for both NO and NO2 as needed in order to maintain this accuracy level.
- Connect an accurate emissions analyzer to the exhaust.
- Start the engine. Allow the engine to warm to normal operating temperature. Increase the engine speed to a minimum of high idle. Set the engine load to a minimum of 50 percent.
- Turn on the power to the emissions analyzer. Allow the NO X reading on the analyzer to stabilize.
- Establish communication between Caterpillar Electronic Technician (ET) and the engine Electronic Control Module (ECM).
- Disable the emissions feedback.
- Use the emissions analyzer to measure the exhaust emissions. Adjust the power screw in order to achieve the desired level of emissions for the site.
- Enable the emissions feedback. Verify that the emissions meet the desired setting. If the emissions are not within ± 10 ppm of the desired NOx, proceed to the next step.
- Access the "Service/Calibrations/Engine Exhaust NOx Level Sensor" calibration screen on Cat ET. Follow the prompts that guide you through the calibration procedure.
- Compare the NOx value on Cat ET to the value on the exhaust analyzer.
- Use the buttons at the bottom of the screen to adjust the NOx slope to match the NOx value on the emissions analyzer. Adjust the slope to a value that is within ± 10 ppm.
Make small adjustments to the slope during the calibration procedure. Allow the engine operation to stabilize after each adjustment. If large changes are made, engine operation may become unstable.
Once the NOx on Cat ET is within ± 10 ppm of the NOx value on the emissions analyzer, the calibration is complete.
- Operate the engine at the rated load. Adjust the exhaust bypass valve until the desired turbocharger compressor outlet pressure and inlet manifold pressure are achieved. Refer to the Technical Marketing Information (TMI) for the engine serial number.
- Record the data from Cat ET for all of the status groups. Save the data for future reference.
Note: Do not allow the engine to operate the air/fuel ratio control in the "Feedback Disabled" (open loop) mode unattended. If any changes are made to the engine timing or to the exhaust bypass setting, check the air/fuel ratio with an emissions analyzer. Adjust the air/fuel ratio again, fi necessary.
For information about the actuator linkage, refer to Specifications, "Actuator Linkage".