On-board diagnostics for an opposed-piston engine equipped with a supercharger

1. A system for diagnosing supercharger operation in an opposed-piston engine including at least one cylinder with piston-controlled exhaust and intake ports near respective ends of the cylinder, a charge air channel to provide charge air to at least one intake port of the engine, and a supercharger having an inlet and an outlet in the charge air channel, the system comprising:

a first gas pressure sensor for measuring a supercharger inlet pressure in the charge air channel;

a second gas pressure sensor for measuring a supercharger outlet pressure in the charge air channel;

a mass airflow sensor for measuring mass airflow in the charge air channel; and,

an engine control unit in signal communication with the first gas pressure sensor, the second gas pressure sensor, and the mass airflow sensor and configured to diagnose operation of the supercharger by:

determining a supercharger mass flow value based on first measurements of supercharger inlet pressure and supercharger outlet pressure;

determining a charge air channel mass flow value based on a mass airflow measurement;

comparing the supercharger mass flow value with the charge air channel mass airflow value; and,

determining whether the supercharger is operable to provide compressed charge air to the at least one intake port based on the comparison.

2. The system of claim 1 , in which determining whether the supercharger is operable includes causing a supercharger on-board diagnostic (OBD) fault indication to be output based on the comparison.

3. The system of claim 1 , in which the opposed-piston engine further includes a supercharger bypass valve in fluid communication with the charge air channel downstream of the supercharger outlet and a position sensor for measuring a bypass valve position, and the engine control unit is operable to determine whether the supercharger bypass valve is operable based on the bypass valve position.

4. The system of claim 3 , in which determining whether the supercharger bypass valve is operable includes causing a supercharger bypass valve OBD fault indication to be output based on the bypass valve position.

5. The system of claim 1 , in which the opposed-piston engine further includes a supercharger variable-speed drive coupled to drive the supercharger, and the engine control unit is operable to determine whether the supercharger variable-speed drive is operable based on second measurements of supercharger inlet pressure and supercharger outlet pressure made at first and second speed ratio settings of the variable-speed drive.

6. The system of claim 5 , in which determining whether the supercharger variable-speed drive is operable includes causing supercharger variable-speed drive OBD fault indication to be output based on the second measurements.

7. The system of claim 6 , in which the opposed-piston engine further includes a supercharger bypass valve in fluid communication with the charge air channel downstream of the supercharger outlet and a position sensor for measuring bypass valve position, and the engine control unit is operable to determine whether the supercharger bypass valve is operable based on the bypass valve position.

8. The system of claim 7 , in which determining whether the supercharger bypass valve is operable includes causing supercharger bypass valve OBD fault indication to be output based on the bypass valve position.

9. The system of any one of claims 1 - 8 , in which the opposed-piston engine further includes an exhaust gas recirculation (EGR) channel and determining the charge air channel mass airflow value includes combining the charge air channel mass airflow measurement with a measurement of exhaust flow in the EGR channel.

10. The system of any one of claims 1 , 3 , and 5 further including a monitor which is operable to cause output of an OBD fault in response to a trigger indicating a determination that the supercharger is not operable, the supercharger bypass valve is not operable, or the supercharger variable-speed drive is not operable.

11. A method of on-board diagnosis (OBD) of air handling system faults of an opposed-piston engine including at least one cylinder with piston-controlled exhaust and intake ports near respective ends of the cylinder, a charge air channel to provide charge air to at least one intake port of the engine, and a supercharger having an inlet and an outlet in the charge air channel, the method comprising:

determining a supercharger mass flow value;

determining a charge air channel mass flow value;

comparing the supercharger and charge air channel mass flow values; and,

determining whether the supercharger is operable to provide compressed charge air to the at least one intake port based on the comparison.

12. The method of claim 11 , further including providing a supercharger OBD fault indication if the supercharger is determined not to be operable.

13. The method of claim 11 , in which the opposed-piston engine further includes a supercharger bypass valve in fluid communication with the charge air channel downstream of the supercharger outlet and a position sensor for measuring bypass valve position, and the method further includes determining whether the supercharger bypass valve is operable based on the bypass valve position.

14. The method of claim 13 , further including providing a supercharger bypass valve OBD fault indication if the supercharger bypass valve is determined not to be operable.

15. The method of claim 11 , in which the opposed-piston engine further includes a supercharger variable-speed drive coupled to drive the supercharger, the method further including determining whether the supercharger variable-speed drive is operable based on measurements of supercharger inlet pressure and supercharger outlet pressure made at first and second speed ratio settings of the variable-speed drive.

16. The method of claim 15 , further including providing a supercharger variable-speed drive OBD fault indication if the supercharger variable speed drive is determined not to be operable.

17. The method of claim 16 , in which the opposed-piston engine further includes a supercharger bypass valve in fluid communication with the charge air channel downstream of the supercharger outlet and a position sensor for measuring bypass valve position, and the method further includes determining whether the supercharger bypass valve is operable based on the bypass valve position.

18. The method of claim 17 , further including providing a supercharger bypass valve OBD fault indication if the supercharger bypass valve is determined not to be operable.