This paper presents a critical review of effect of intake manifold flow to four stroke single cylinder engine performances. Intake manifold and its components play critical role in deciding the performance of engine. Engine can be easily breathing related to flow pattern by best design of intake manifold that can contribute to performance. Flow pattern of intake manifold affect the volumetric efficiency, mass flow rate and velocity which ultimately makes impact up on the engine power & torque. This paper reviews work done by various prominent researchers in the field of intake tuning and variable intake manifold. It can be easily concluded that for getting best flow pattern of intake manifold throughout the engine operating speed the intake geometry need to be changed.
