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The unsteady gas dynamic phenomena in a racecar airbox have been examined, and resonant tuning effects have been considered. A coupled 1D/3D analysis, using the engine simulation package Virtual 4-Stroke and the CFD package FLUENT, was used to model the engine and airbox. The models were experimentally validated. An airbox was designed with a natural frequency in the region of 75 Hz. A coupled 1D/3D analysis of the airbox and a Yamaha R6 4-cylinder engine predicted resonance at the single-cylinder induction frequency; 75 Hz at an engine speed of 9000 rpm. The amplitude of the pressure fluctuation was found to be influenced by the separation between the intake pipes in the airbox. For an n-cylinder even-firing engine, if the intakes are coincident in the airbox, then the fundamental and all harmonics of the forcing function, apart from the (n-1)th, (2n-1)th, etc. will cancel. That is, only the multi-cylinder induction frequency and its multiples will not cancel.