Abstract: A control system for a vehicular power plant including an automatic transmission and an exhaust brake. The exhaust brake includes a butterfly valve movably disposed in an exhaust pipe. The control system is comprised of a control unit which is supplied with a signal representative of an engine brake condition and is adapted to generate a signal commanding an automatic downshift of the automatic transmission. Under the operation of the control unit, the exhaust brake is temporarily put into an inoperative condition in response to both the detected engine brake condition and the downshift command.

Abstract: A control system for a vehicular power plant including an automatic transmission and an exhaust brake. The exhaust brake includes a butterfly valve movably disposed in an exhaust pipe. The control system is comprised of a control unit which is supplied with a signal representative of an engine brake condition and is adapted to generate a signal commanding an automatic downshift of the automatic transmission. Under the operation of the control unit, the exhaust brake is temporarily put into an inoperative condition in response to both the detected engine brake condition and the downshift command.

Abstract: An engine brake control system generally engages an overrun clutch in overall throttle valve open angle range at operational ranges for effecting engine brake. The control system is responsive to variation of selected operational range from a high transmission speed ratio range for automatic speed ratio selection to the engine braking range for establishing engagement of the overrun clutch with a predetermined lag time. The predetermined lag time is adjusted depending upon the vehicle driving condition.