| 摘要 |
PURPOSE:To prevent the prefiring of exhaust gas at the time of opening an intake valve by connecting two intake ports provided on each of cylinders by means of a connecting passage, and specifically setting the deviation angle of opening timing between both intake ports. CONSTITUTION:The intake system of a four-cylinder engine 1 consists of a common intake passage 5 having a throttle valve 4, a surge tank 6 connected to the lower course of the passage 5, branched intake passages 7 branched off from the tank 6 toward cylinders #1-#4, and intake ports 8, 9 for low and high loads which are branched off in two from each of the passages 7 by means of partition walls 30 on their lower courses. Both of the intake ports 8, 9 are mutually connected by means of a connecting passage 32 on the lower course part of the branched intake passage 7. In this case, when the rated speed of an engine 1 is defined as Nmax, connecting distance between both intake ports 8, 9 as l, the deviating angle of opening timing between both intake port 8, 9 as DELTAtheta, and a sonic velocity as (a), DELTAtheta is set so as to satisfy a formula, Nmax>=(DELTAthetaX60Xa)/(360Xtheta).
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