Lots of design concepts for intake ports of SI engines have been introduced due to their significant effects on in-cylinder flow pattern and volumetric efficiency. However, those efforts have been made usually based on port experts' experience, which means that systematic analyses are not well established. As an attempt for improving the situation, an investigation has been performed to analyze experimental results and correlate them with port design parameters in this study.
Twenty-eight SI engines, which cover a wide range of displacement volume from 1,000cc to 4,500cc, were tested to evaluate port Cf (Flow Coefficient). Except two small engines, these are four-valve engines with a pent-roof combustion chamber. The test results were analyzed with different port shapes, which were defined by several port design parameters. The parameters were chosen to be easily measured in the real intake ports and then re-defined for further analyses by appropriate non-dimensional arrangements. These comparisons finally revealed correlations between the parameters and Cf. They also provided design guidelines how to determine those parameters for a better port performance.
The most effective design parameters on Cf were found. They were Port Height at the valve guide, Flange Area, Port Size represented by Valve Head Diameter, and the ratio of Port Size and Bore etc. The equation that related these parameters and Cf showed an excellent correlation. The differences in Cf between calculated and measured were only within 2%. In the second part of the study, new intake ports were designed mainly in terms of Port Height and their Cf were evaluated to confirm the effects of the design parameters on Cf.