Conditions at the intake valve of an operating SI engine

While improved additive packages for gasoline have essentially solved the original problem of poor performance during warm-up, the solution was achieved without completely understanding the mechanism by which intake valve deposits from or through which additives work. The purpose of the present investigation is to obtain information that will aid in the understanding of the mechanism of intake valve deposit formation and the role of key variables like valve temperatures and intake charge composition. The conditions at the intake valve of a GM 2.0 liter four cylinder engine have been determined at two test conditions. Measurements of temperatures of the valve surface indicate significant differences between a low power and high power condition. Also, the composition of the gases in these two cases was clearly different and indicated a greater level of EGR at high power. The results presented in this paper form the basis for understanding any differences that may arise when this study is extended to investigate deposit levels at these test conditions.