Engine Particulate Emissions as a Function of Gasoline Deposit Control Additive

Understanding the sources of vehicle particulate emissions is paramount for automotive companies to comply with worldwide emission regulations. Previous work has shown that fuel composition [1] and engine carbon deposits [2] both play a part in particulate emissions. More specifically, gasoline Deposit Control Additive (DCA) studies have shown the emissions benefits of removing and/or preventing these carbon deposits, including Particulate Mass (PM) emissions [3]. This study examines the instantaneous, in-cylinder combustion effects of gasoline DCA on PM emissions independent of engine deposit effects. Formulated detergent packages of the three main chemistry types of global market gasoline DCAs were evaluated in a basefuel at four concentrations to determine the impact on PM emissions. To minimize contributions from engine deposits, a test engine with a very low deposit formation tendency was chosen. Each chemistry and concentration were tested over a series of four consecutive tests, including one cold-start cycle. The results are shown as an average PM rate in milligram per kilogram (mg/kg), which are useful for comparison only in this study. These instantaneous, combustion-related particulate results were then compared to a final test sequence of accumulated engine deposits to compare PM emissions rates. The results show that the PM emissions for two of the three DCA packages tested were not linear, indicating an optimal concentration of DCA, which is neither the lowest nor highest concentrations tested. The optimal DCA concentrations correlated with the TOP TIER™ Detergent Gasoline standard. All tests at the highest tested DCA concentration statistically increased PM emissions over the basefuel baseline emissions rate. However, the tests revealed the PM emissions were highest on the tests after engine deposits had built up. In summary, this study indicates that it is not only important to control engine deposits but also to utilize the correct concentration of gasoline DCA to minimize vehicle PM emissions.