Investigation into the Performance of an On-Board Emissions Measurement System using a Vehicle Exhaust Emissions Simulator

A vehicle-mounted emissions measurement system that continuously measures CO, CO₂, HC, NOx, and A/F as concentrations and also measures exhaust gas flow rate, mass emissions and fuel consumption is presented. The limitations of the accuracy and precision of the on-board emissions system are characterized using a vehicle exhaust emissions simulator. The simulator provides accurate simulated exhaust flows in the range of 10-120 SCFM. The simulator has demonstrated in tests of injected versus recovered CVS mass emissions an overall accuracy of approximately 0.5% of the requested values. The simulated exhaust tests include both fixed and transient concentrations, as well as simulations of an EPA-75 test for a typical vehicle..