Pressure measurements were conducted and airflows were visualized inside the intake manifold to help enable an overall understanding to be obtained of the phenomenon of noise occurring under conditions of rapid throttle opening during engine operation. The use of plastic intake manifolds and drive-by-wire (DBW) has made this noise more conspicuous. The results of attempts to identify the sound source showed that the noise was radiated from the surface of the intake manifold. For measurements of the behavior of the airflows inside the intake manifold, airflows were visualized while the engine was in operation using a high-speed camera (taking advantage of recent performance enhancements) and a special lighting system in a method that can be applied during the development process. The results of these measurements demonstrated that noise resulting from the collision of high-speed airflows is the origin of the noise under study.
Article of Honda R&D Technical Review Vol.24 No.1 (69 - 75)