Induction tuning of intake manifolds of internal combustion multicylinder engines has been carried out by various devices. Tuning maximizes air flow by minimizing or counteracting the effects of standing waves and other acoustic phenomena generated in the air induction system.
An expansion chamber resonator is one such device, in which the induction air flow passes into a relatively large volume chamber, and thence into the engine. The expansion chamber prevents the formation of large amplitude standing waves and dissipates the sound energy in the system. However, the use of such resonator chamber devices often still result in a characteristic decline in engine torque at a particular narrow range of engine speeds, since expansion chamber resonators typically are not effective at all noise frequencies.
U.S. Pat. No. 4,539,947 issued on Sep. 10, 1985 for a "Resonator for Internal Combustion Engines" describes a solution for the above problem involving a computer controlled variation of resonator geometry to increase the effective range of the resonator.
Another device is the "Helmholtz" resonator which comprises a chamber which does not receive the induction air flow, but is in communication with the air flow path via a small diameter opening. The resonance of the Helmholtz resonator is limited to a narrow range of engine speeds and thus is not effective over the entire operational range of engine speeds, and hence it has also been proposed to provide an adaptive Helmholtz resonator which is tuned differently over a range of varying engine speeds design.
Such approach, while effective, adds considerable complexity to the device.
It is an object of the present invention to provide engine air induction tuning by completely passive means.