Emissions and Fuel Economy Test Methods and Procedures For Light Duty Motor Vehicles-A Critique

The reliability and reproducibility of both exhaust emissions and fuel economy measurements for light duty motor vehicles are strongly influenced by the specified test methods and procedures. In this paper, the statistical variability of CVS-CH exhaust emission tests for light duty motor vehicles and the relative magnitudes of the various factors affecting errors encountered during the tests are discussed. Additional questions concerning the affect of ambient temperature on exhaust emissions and data relating to the effectiveness of present evaporative HC emission test methods and procedures are considered. In addition, the critical elements in any standardized fuel economy test method and procedure are discussed and data associated with the statistical variability of present fuel economy measurements is presented.