Investigating the Effect of a Sonic Restrictor in the Intake of an Engine

This document explores the development and integration of a quasi-1D sonic restrictor model within a Dymola and Modelica-based engine simulation framework to investigate the effects of choked airflow conditions in restricted racing engines.

Using a naturally aspirated four-cylinder motorcycle-derived engine and Mean Value Engine Models (MVEM), the study analyses how varying sonic restrictor throat diameters influence intake airflow, volumetric efficiency, engine torque, and power generation as engine speed increases and supersonic shock conditions occur within the intake nozzle. By modelling compressible flow behaviour, shock formation, pressure losses, and sonic choking without computationally expensive CFD simulations, the research demonstrates how intake restrictor geometry significantly affects engine performance and highlights the importance of predictive multi-domain simulation tools for restricted motorsport engine development, intake optimisation, and powertrain calibration.