Improvement of the Torque Characteristics of a Small, High-Speed Engine Through the Design of Helmholtz-Tuned Manifolding

Manifolding for a 600cc four-stroke engine to be used to power a vehicle entered in the 1989 student Formula SAE® competition was tuned to maximize mid-range torque. Although powerful computer programs exist to analyze manifold wave dynamics, these programs are unavailable to the public; lacking access to these types of programs, Helmholtz tuning theory was chosen for use in this work due to its straightforward computational methods. Although the assumptions of Helmholtz tuning theory may not rigorously apply at high engine speeds, it was successfully used to provide design guidelines for the selection of manifolding physical parameters, and was applied successfully to increase engine output. Intake tuning of the engine with the required restrictor and single carburetor yielded torque levels of as much as 12% higher than the unrestricted stock engine with four carburetor set-up. Exhaust system tuning using the same theory succeeded in developing an exhaust system that complemented the intake system tuning, together producing as much as 34% more torque than the unrestricted stock engine.