Intake tuning is a significant method of boosting performance by enhancing volumetric efficiency in a naturally aspirated engine. Elements of intake tuning can involve varying intake runner length, geometry and plenum shape and volume. Previous research has demonstrated the beneficial effects of increasing plenum volume on engine torque. This objective of this study was to evaluate the ability of analytical and two computer based models (simple and complex) to accurately predict the effects of varying plenum volume on steady state and transient engine performance for a small restricted spark ignition engine. The computer models were only moderately successful in characterizing steady state performance. The simple model matched torque peak locations but failed to adequately predict the advantageous effect of plenum volume on torque. The complex model more effectively simulated torque effects of plenum volume increase but did not adequately capture torque peak locations. Both models underestimated mid-range torque by up to 20%. Transient manifold filling was estimated well with both the complex computer model and analytical methods. Transient torque response differed by only 1–2 engine cycles and was also well predicted by the computer simulation.

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