Abstract: Failure of a valve timing changeover control system of an internal combustion engine is detected by the steps of: (1) setting a predetermined state of intake air to be supplied to the engine depending on a control signal for controlling changeover of valve timing, (2) detecting a state of intake air being supplied to the engine, (3) comparing the detected state of intake air with the set predetermined state of intake air, and (4) detecting from the result of the combustion whether or not there is failure in the valve timing changeover control system.

Abstract: A cylinder head structure for a multiple cylinder engine, comprising, at least for each of its cylinders (1) located at either longitudinal end of its cylinder bank: a combustion chamber (13) defined by the cylinder and a piston received therein; an intake passage (18) communicated with an intake manifold (20) at its one end and with said combustion chamber at its other end; and exhaust passage (19) communicated with an exhaust manifold (21) at its one end and with said combustion chamber at its other end; at least one of said intake passage and said exhaust passage being curved toward a longitudinally central part of said cylinder bank as it extends from its other end to its one end. Hence, the size and weight of the intake manifold and/or the exhaust manifold can be reduced.

Abstract: An intake air flow control apparatus for an internal-combustion engine, which includes a valve lift characteristic control means for variable control of the lift characteristics of intake and exhaust valves for the internal-combustion engine and a deceleration intake control means for controlling the quantity of intake air to be supplied to the downstream side of the intake throttle valve during the deceleration operation of the engine, comprises an intake control characteristic change means for changing the control characteristics of the deceleration intake control means in response to the valve lift characteristic control.

Abstract: A method of controlling the supply of fuel to an internal combustion engine having first and second fuel injection valves arranged in the intake passage downstream and upstream of the throttle valve, respectively, both being upstream of the intake manifold wherein the first and second fuel injection valves are selectively operated to supply fuel to the cylinders in dependence on operating conditions of the engine. Fuel is supplied to a plurality of cylinders of the engine through the first fuel injection valve alone when the engine is operating in a predetermined low load condition. In a middle/high load middle speed region of the engine, a substantially constant minimum required quantity of fuel is supplied through the first fuel injection valve, and simultaneously a quantity of fuel appropriate to the middle/high load middle speed region is supplied through the second fuel injection valve.

Abstract: A fuel supply control system for an internal combustion engine having a fuel injection valve arranged within a suction passage at a location upstream of an intake manifold and a throttle valve therein, and an air throttle valve arranged within the suction passage at a location upstream of the throttle valve and having a throttle opening disposed to be positioned opposite the nozzle of the fuel injection valve when the air throttle valve is fully closed whereby intake air flows through the throttle opening in the vicinity of the nozzle of the fuel injection valve at an increased speed. The system controls a quantity of fuel supplied to a plurality of cylinders of the engine in accordance with operating conditions of the engine. Further, the system increases the quantity of fuel when the air throttle valve is opened.