Abstract: In an engine induction system, a drive frequency f1 of an ISC valve 13 for duty control and a characteristic frequency f2 of an intake passage between an air cleaner 8 and a throttle valve 11 are set so as to obtain a relationship: (3/4)f1.ltoreq.f2.ltoreq.(5/4)f1. In this set system, a resonance chamber 17 is connected to the intake passage between the air cleaner 8 and the throttle valve 11 to thereby deaden the vibration caused by the driving of the ISC valve 13. Accordingly, the engine induction system is allowed to prevent the amplification of the vibration accompanying the actuation of the ISC valve so as to prevent the deterioration of the detection accuracy of an airflow meter while being allowed to meet requirements such as an improvement in the responsiveness when the ISC valve disposed in an ISC pipe is duty controlled.

Abstract: An induction system for use in a V-shaped engine having a forward bank and a rearward bank each provided with a row of cylinders, the induction system includes intake runners individually extending from the cylinders of each bank, the intake runners being convergedly connected at upstream end portions respectively. To upstream ends of thus converged connection portions are connected common intake passages, which are connected to a junction portion at a further upstream side, whereby the respective common intake passages are connected. The lengths of the intake runners from the cylinders up to a center of the converged connection portion are set equal to one another. The respective converged connection portions are arranged vertically above the rearward bank. A communicating passage is provided for communicating the center portions of the respective converged connection portions with each other.

Abstract: In the present invention, in addition to a main throttle valve which is conventional, a sub-throttle valve for exclusive use of a mechanical supercharger is provided. By this sub-throttle valve, a flow rate of intake air is throttled by a fixed amount when the mechanical supercharger is switched from a non-connected state to a connected state. This makes it possible to prevent supercharged air from being bypassed to upstream of the supercharger through a bypass and also prevents generation of air intake noises. Moreover, in the case where the mechanical supercharger is of a type involving interior compression, at the time of the switching operation torque shock can be prevented and controllability of engine output by an accelerator pedal is improved.

Abstract: A V-type engine has a plurality of cylinders formed in a pair of cylinder banks. An intake system for the V-type engine includes a surge tank which is communicated with the atmosphere through a common intake passage provided with a throttle valve, discrete intake passages which branch off from the surge tank and are connected to the responsive cylinders, branch passages which branch off from the respective discrete intake passages, one or more volume chambers each of which is communicated with at least two of the branch passages, on-off valves which are respectively provided in the branch passages and are opened and closed according to the operating conditions of the engine. The surge tank is disposed above one of the cylinder banks and the volume chamber or volume chambers are disposed above the other cylinder bank.

Abstract: In a V-type internal combustion engine having a pair of upwardly diverging cylinder banks and an auxiliary unit disposed at an upper portion in a space defined between the cylinder banks, a suction arrangement includes intake ports provided at an inner side of the respective cylinder banks, inclined inwardly by a predetermined angle with respect to respective clyinder axes, and extending upwardly in a generally vertical direction so as not to interfere with the auxiliary unit, and cylinder communicating portions connected to upper portions of the intake ports in communication with the respective cylinders to permit the introduction of the intake gas thereto.

Abstract: An air suction device for a multicylinder engine comprises a first group of inlet passages each having one end connected to one of a first group of cylinders, a second group of inlet passages each having one end connected to one of a second group of cylinders, a surge chamber separated off by a partition-wall into first and second compartments for air expansion provided with a plurality of first openings each coupled with the other end of one of the first group of inlet passages and a plurality of second openings each coupled with the other end of one of the second group of inlet passages, respectively, and a valve unit including a body member forming an air passage and a closing valve disposed in the body member for closing selectively the air passage.

Abstract: An induction system for a V-type internal combustion engine having a first and second banks respectively constituted with a plurality of cylinders and shifted with respect to each other in the direction of alignment of the cylinders, including intake ports provided to face a space between two banks, surge tank means for leading intake air to each intake port arranged above one of the banks, first intake passage means curvedly formed for feeding intake air from the surge tank means to the cylinders of the first bank, each being connected with the side portion of the surge tank means at one end thereof and with one of the intake ports of the cylinder of the first bank at the other end thereof and consisting of an upstream intake passage means and a downstream passage means, and second intake passage means curvedly formed for feeding intake air from the surge tank means to the cylinders of the second bank, each being connected with the side portion of the surge tank means at one end thereof and with one of the i