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This paper describes a method for the rapid generation of a first estimate of engine tuning parameters for a 4-cylinder naturally aspirated spark ignition engine. These parameters involve the primary lengths and diameters of the intake and exhaust systems. These variables were optimised for peak power over a range of different speeds and for different engine capacities. A 4-cylinder engine was modelled in GT-Power, a one-dimensional engine cycle simulation package. All the above variables were included in the model and a number of assumptions made about the base engine design for each optimisation point. A range of values for all the variables were analysed within a DOE matrix. The resulting response surfaces can be used to give approximate tuning dimensions to provide a starting point for packaging studies and more detailed simulations immediately on commencing a new project.

A study of the fundamental design characteristics of SI engine inlet ports is presented. The work involved the parameterisation of inlet port design features to enable a simplified description of the fundamental form of a port to be made. A parametrically controlled CAD model was then created to enable variations in port geometry to be generated quickly and surface meshes created for CFD analysis. CFD analysis and Design of Experiments were employed to establish the relationship between design parameters and port flow characteristics. Correlation of the CFD results was established via the use of a number of rapid prototype port models, tested on a flow bench. To aid interpretation of the data, a computer emulation of the results with a Graphical User Interface (GUI) was produced using MATLAB software. The resultant GUI is available for use as a tool to highlight the effects of key design parameters during the concept and optimisation stages of inlet port design.