Abstract: There are provided on an upper surface of a piston 13 which confronts to a combustion chamber two first squish areas A1 each containing a flat surface 13a extending along an outer circumferential portion the piston 13 in an arc-like fashion and two second squish areas A2 formed between valve recesses 13d, 13e of respective pairs of inlet and exhaust valves 19, 21 and each containing a protruding portion which protrudes upwardly.

Abstract: A control system for an internal combustion engine, which is capable of reducing exhaust emissions during and after the start of the engine. A control system is capable of changing the valve-closing timing of intake valves relative to the valve-opening timing thereof as desired using a variable intake valve actuation assembly. The control system includes an ECU. The ECU sets a target auxiliary intake cam phase to a start value that sets the valve-closing timing of the intake valves to retarded-closing timing, during starting of the engine, and to a catalyst warmup value that sets the same to timing closer to timing in the Otto cycle operation, during catalyst warmup control after the start of the engine.

Abstract: A valve timing control system for an internal combustion engine, which is capable of accurately and delicately controlling an amount of intake air, and thereby maintaining excellent combustion state and reduced exhaust emissions. The valve timing control system variably controls the valve-closing timing of an intake valve with respect to valve-opening timing of the same as desired via a variable intake valve actuation assembly. The ECU of the engine determined a basic value of a target auxiliary intake cam phase according to the demanded drive torque of the engine. The ECU calculates a control input to the variable intake valve actuation assembly such that the cylinder intake air amount converges to a target intake air amount and at the same time the auxiliary intake cam phase is constrained to the basic value of the target auxiliary intake cam phase.

Abstract: There are provided on an upper surface of a piston 13 which confronts to a combustion chamber two first squish areas A1 each containing a flat surface 13a extending along an outer circumferential portion the piston 13 in an arc-like fashion and two second squish areas A2 formed between valve recesses 13d, 13e of respective pairs of inlet and exhaust valves 19, 21 and each containing a protruding portion which protrudes upwardly.