Development and Validation of an Impedance Transform Model for High Speed Engines

Acoustical tuning of intake manifolds is a common practice used to achieve gains in volumetric efficiency in a pre-determined region on the torque curve. Many methods exist for acoustical tuning of the intake including a variation of the Helmholtz resonator model by Engelman as well as the organ pipe models by Ricardo and Platner. In this work a new intake tuning model has been developed using an Impedance Transform Model along with a minimal set of limiting assumptions. Unlike the models of Engelman and Platner, this model can accommodate any intake geometry. The model can also be used to analyze specific points in the intake system or the entire system rather than just the intake runners. Model verification consisted of resonance testing of three different Helmholtz resonators as well as dynamometer testing of a Honda CBR F3 four-stroke SI engine using three different intake system geometries. The different intake systems and Helmholtz resonators were designed such that each would produce different resonant frequencies for proper model verification. The model accurately predicted the resonant frequencies of each different Helmholtz resonator and the torque peak produced by each intake system iteration.