An engine induction system.

摘要

An induction system for use in a V-shaped engine (1) having a forward bank (Bf) and a rearward bank (Br) each provided with a row of cylinders (51, 53, 55, 52, 54, 56), the induction system includes intake runners (7f, 7r/107f, 107r) individually extending from the cylinders (51-56) of each bank, the intake runners (7f, 7f/107f, 107r) being convergedly connected at upstream end portions respectively. To upstream ends of thus converged connection portions (9f, 9r/109f, 109r) are connected common intake passages (10f, 10r/131, 132), which are connected to a junction portion (11/133) at a further upstream side, whereby the respective common intake passages (10f, 10r/131, 132) are connected. The lengths of the intake runners (7f, 7r/107f, 107r) from the cylinders (51-56) up to a center of the converged connection portion (9f, 9r/109f, 109r) are set equal to one another. The respective converged connection portions (9f, 9f/109f, 109r) are arranged vertically above the rearward bank (Br). A communicating passage (12/121a, 121b) is provided for communicating the center portions of the respective converged connection portions (9f, 9r/109f, 109r) with each other. In the communicating passage (12/121a, 121b) is provided a valve (122) for opening or closing the communicating passage (12/121a, 121b) according to an engine speed. In this induction system, the dynamic effects of induction can be efficiently utilized in a wide range of engine speed in a relatively simplified construction. In addition, an intake manifold can be arranged in such a manner as to make the size of the engine smaller.