Inference of Torque and Power from Heavy-Duty Diesel Engines for On-Road Emissions Monitoring

Increased concerns about the emissions produced from mobile sources have placed an emphasis on the in-use monitoring of on- and off-road vehicles. Measuring the emissions emitted from an in-use vehicle during its operation provides for a rich dataset that is generally too expensive and too time consuming to reproduce in a laboratory setting. Many portable systems have been developed and implemented in the past to acquire in-use emissions data for spark ignited and compression ignited engines. However, the majority of these systems only measured the concentration levels of the exhaust constituents and or reported the results in time-specific (g/s) and or distance-specific (g/km) mass units through knowledge of the exhaust flow. For heavy-duty engines, it is desirable to report the in-use emission levels in brake-specific mass units (g/kW-hr) since that is how the emission levels are reported from engine dynamometer certification testing. Only a few portable systems have attempted to report the emissions in brake-specific mass units and have met with limited success. A method to infer the load and power is presented for modern, electronically controlled, compression ignition engines. The associated errors with this method are detailed along with a comparison for three different engines. The results show that the errors are on the order of 5 to 10% but can be as low as 1% when the cumulative energy is averaged for a transient cycle for a well-maintained engine operating through the FTP cycle.