Development of a Practical Correlative I/M Exhaust Emission Test

The 1990 amendment to the Clean Air Act (CAA) mandates enhanced inspection and maintenance (I/M) programs for the three most severely polluted nonattainment area classes. The State of Arizona Emissions Research Laboratory (ERL) is currently studying alternative methods, procedures, and equipment to determine the minimum technological limits required to produce acceptable Federal Test Procedure (FTP) correlative data and avoid excessive test precision losses. The first phase of the study, development of the driving trace, has shown that a 95 second loaded transient test (AZ95) yields results that are statistically similar to the 240 second loaded transient test (IM240) with respect to test repeatability and correlation to FTP derived tailpipe emissions.