Characterization of Deposits Formed in Automotive Engines

Deposits formed in different parts of automotive engines were characterized by analytical techniques. Also, the methods for clarifying the formation factors of the deposits, such as the formation origins, formation environments and formation routes, were investigated. First, the deposits were classified into three types of ten components based on the difference in their formation origins: four components derived from fuel, three components from engine oil and three components from particulate matter contained in the intake air. Next, the characteristics of these components were examined by four kinds of analytical techniques. The results are as follows. The ten components defined above could be distinguished from one another by four kinds of analytical indexes: chemical structure, elemental composition, thermal gravimetric property and solubility. Of the components, seven of these derived from the fuel and engine oil reflect the environment of the thermal load and the oxygen concentration at the time of deposit formations. Therefore, the formation environment of a target deposit could be estimated from the deposit composition determined by the analytical indexes. Furthermore, the deposit formation routes, which vary with different gas flows and oil flows of the engine inside, could be estimated in two ways. If the formation routes were limited in advance, it would be effective to examine the composition differences between a target deposit and the deposits of each expected route. If the formation routes were uncertain, it would be effective to examine the difference in the component distribution contained in a target deposit.