The Role of Intake Manifold Geometry on Airflow Dynamics and Combustion Efficiency: A Computational and Experimental Review

Abstract

The geometric configuration of the intake manifold assumes a crucial function in influencing the aerodynamic behavior and combustion efficacy of internal combustion engines (ICEs). This comprehensive review amalgamates both computational and experimental investigations to assess the influence of manifold design parameters on engine performance metrics, volumetric efficiency, and emission profiles. A systematic literature review was executed utilizing the Scopus database, employing Boolean search operators to identify 18 significant studies published between 2008 and 2025. The methodologies encompassed computational fluid dynamics (CFD) simulations, empirical validations, and performance indicators such as torque, fuel consumption, and pollutant emissions. The principal findings indicate that variable-length manifolds can enhance volumetric efficiency by 8–15% by tuning Helmholtz resonance, albeit at the expense of increased cost and complexity. Fixed-geometry configurations yield 5–7% torque improvements at resonant frequencies, yet they exhibit suboptimal performance beyond their specified operational ranges. This study accentuates the necessity for application-specific designs that harmonize performance, cost, and emissions. Future investigations should delve into adaptive geometries that utilize additive manufacturing techniques and enhance transient-state modeling to overcome existing challenges. This review establishes a framework for engineers to refine intake manifold designs, highlighting the intricate relationship between geometry, fluid dynamics, and combustion efficiency.