Abstract: An engine is provided with a primary turbocharger and a secondary turbocharger having blowers disposed in the intake passage of the engine in parallel to each other and turbines disposed in the exhaust passage of the engine in parallel to each other. An exhaust cutoff valve disposed in the exhaust passage opens to feed exhaust gas to the turbine of the secondary turbocharger to operate the secondary turbocharger only in a large intake air mass range. A waste gate valve opens to relieve exhaust gas fed to the turbochargers when the supercharging pressure exceeds a predetermined value. The waste gate valve is kept closed for a predetermined time after the operating condition of the engine shifts into the large intake air mass range and the exhaust cutoff valve opens when shift of the operating condition of the engine from a small intake air mass range to the large intake air mass range is required.

Abstract: An engine is provided with primary and secondary turbochargers. In a small intake air mass range, only the primary turbocharger is caused to operate, and in a large intake air mass range, both the primary and secondary turbochargers are caused to operate. A waste gate valve and an exhaust bypass valve are controlled so that the supercharging pressure approximates to a target supercharging pressure. The target supercharging pressure in the large intake air mass range is set lower than that in the small intake air mass range.

Abstract: A control system for supercharging an internal combustion engine equipped with an automatic transmission includes a capacity changeable supercharger. The supercharger is controlled by a supercharging capacity controller, having data representative of at least one supercharging capacity control line, so that its supercharging capacity is charged according to operating conditions of the internal combustion engine. A transmission shift controller, causing the automatic transmission to shift according to operating conditions of the internal combustion engine, has data representative of at least one gear shift control line for a shift operation of the automatic transmission. The at least one gear shift control line has an intermediate portion, including an intersection with the supercharging capacity control line defined by a specific engine load between upper and lower middle vehicle speeds.

Abstract: A transmission control system for an automatic transmission for a vehicle causes the automatic transmission to shift according to one of an economy mode shift pattern and a power mode shift pattern. The control system switches the shift pattern from the economy mode shift pattern to the power mode shift pattern when the engine load or the rate of change of the engine load becomes not smaller than a predetermined reference value. The predetermined reference value is changed according to the acceleration of the vehicle body.