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This paper investigates influences of intake and exhaust valves overlap (at this duration, both of the intake valve and exhaust valve are open) on engine performance. An electric, variable cam phase mechanism (VVT, Variable Valve Timing unit) is installed in a small gasoline engine. The influences on the engine torque and BSFC, Brake Specific Fuel Consumption, are investigated on the engine bench. In addition, in case the overlaps exceeding the experimental range an engine simulator is used to predict the effects. The experimental results indicate that the VVT system can adjust the target overlap with the accuracy of 1.5deg. in a range of engine speed from 3000rpm to 7000rpm. The response time of the VVT unit was observed at the engine speed of 3000rpm. The results show that the rotation direction of motor affects on the response time of the unit. The measurement of engine torque and BSFC is performed for several overlap values at each engine speed.

Cylinder pressure is used for the closed-loop ignition angle control of a gasoline engine. This paper focused on the crank angle position where the maximum cylinder pressure reached (θPmax) and the relationship between the θPmax and the ignition angle. This closed-loop control set the θPmax a target value with an initial ignition angle and does not need a detailed ignition angle map. Response time and deflection with the target value are examined with a test bench. The θPmax target, ATDC 18 deg. is confirmed in consideration of the effect of knocking and the exhaust gas composition. The target ignition angle was varied step by step within a limit of upper and lower values, the response was observed and each gain was decided. At the engine speed of 5000 rpm, the duration to reach a steady value of θPmax is 0.10 s and the response time of ignition angle is 0.02 s.