| 摘要 |
PURPOSE:To obtain an excellent supercharging effect in the medium- and high- load operational range of a two-cylinder engine having two independent systems of intake passages, by constituting each intake port from a main port and an auxiliary port having a control valve for varying the port opening period, and specifying the opening periods of the ports respectively. CONSTITUTION:Low-load intake passages 20(20a, 20b) and high-load intake passages 21(21a, 21b) are connected respectively to low-load intake ports 3 and high- load intake ports 4 formed in each side housing 5 of a two-cylinder engine, and a control valve 16 for varying the port opening period is provided at each high- load intake port 4. The high-load intake port 4 is composed of a main port 4a and an auxiliary port 4b which is opened and closed by the control valve 16 which is opened at the time of high-load operation of the engine when the engine speed is higher than 3,500-5,000rpm. The port opening period of the intake port 4 at the time when the control valve 16 is opened is set in the range of 270- 320 deg. while the port opening period at the time when the control valve 16 is closed is set in the range of 230-290 deg.. Further, the opening period of the low- load intake port 3 is set in the range of 230-290 deg.. |
