PURPOSE: To improve effectiveness of an engine brake and to make speed reducing operation smoothly, by providing a control valve for opening and closing a communication passage for communicating among cylinders and control means for closing the control valve when speed reducing operation is started.
CONSTITUTION: A control valve 14 in a communication hole 13 is provided with an actuator 18. A negative pressure introduction passage 19 for introducing negative pressure of intake air downstream of a primary throttle valve 9 into the actuator 18 is provided with a 3 way solenoid valve 20 and a delay valve 21. When a speed reduction switch 24 connected to a control circuit 22 is turned on, the control circuit 22 actuates the 3 way solenoid valve 20 and the delay valve 21 taking into consideration the time for the primary throttle valve 9 to be closed completely and closes the control valve 14 completely with delay. With such an arrangement, an effective engine brake can be applied for making speed reducing operation smoothly.
YOSHIOKA SADASHICHI
MOTOOKA HIROAKI
