Factors Affecting the Design and Breakthrough Performance of Evaporative Loss Control Systems for Current and Future Emission Standards

For approximately 20 years, activated carbons used in motor vehicle evaporative loss control devices [ELCD] have been selected on the basis of butane saturation working capacity. While this technique served as a useful standard in the past, more stringent evaporative emission regulations coupled with changing automobile designs and changes in gasoline composition have prompted a reexamination of the carbon products used in the ELCD systems and the methods used to predict the carbon performance. Our studies have shown the butane working capacity test to be misleading, and a poor indicator of actual performance. In contrast, a new adsorbent test rig that measures carbon working capacity to breakthrough has been found to be a much more sensitive measurement of a carbon's suitability for meeting the 2 gram SHED emission test.