Impact of fuel characteristics on in-use performance of exhaust catalysts

In order to improve air quality, California has implemented a plan requiring low emission vehicles with advanced technology exhaust catalyst systems. These vehicles are certified and intended to operate on an advanced reformulated gasoline (California Phase 2). Other states have or intend to adopt a similar vehicle program, but although these vehicles will also be certified and designed for operation on the California Phase 2 gasoline, they will in practice be operated on a variety of gasolines, both reformulated and unreformulated. In some regions, enhanced inspection/maintenance tests will periodically be required which includes a test of the exhaust emission control system using a transient driving schedule. These tests will be performed using available commercial fuels, thus we have undertaken a study to determine the impact of several individual fuel properties on the resulting emissions produced during such a test. Properties varied individually include distillation, oxygenate content and sulfur level. In addition, the impact of each variable was measured at several different test temperatures to gain insight on the effect of ambient temperature on in-use emissions. We will discuss the result of these impacts and possible explanations based on additional insight gained from modal (second-by-second) emissions data as well as catalystmore » temperatures logged during the tests.« less