Abstract: A piston of an engine has a bowl including: a top end that is a surface inclined toward a center of the piston from an edge portion of a top of the piston; a central projection protruding upward at a center of the piston; a recession extending outwardly from the central projection and inclined downward beneath the top end; and a neck connecting the recession and the top end to each other wherein a minimum diameter of the neck is within 62˜65% of a cylinder bore diameter, a maximum diameter of the recession is within 102˜105% of the minimum diameter of the neck, a maximum depth from the top of the piston to a deepest portion of the recession is within 10˜20% of the cylinder bore diameter, and a center of a radius of curvature of the neck is disposed within 2˜10% of the cylinder bore diameter.

Abstract: A turbocharger control duty deviation compensation method may include judging a learning condition given deviation of a target position calculated using a turbocharger model and an actual position of a turbocharger together with atmospheric pressure, when a turbocharger control starts with a boost control duty value which matches with a required boost pressure target of an engine based on controller, calculating a learning value based on (100?target control duty)/(100?actual control duty) when the control duty deviation compensation control of the target control duty value calculated using the turbocharger actuator control duty model and the actual control duty value of the turbocharger are necessary, and acquiring a control to which any difference in the hardware-based characteristics of the driving mechanism related to the turbocharger are reflected since the control duty value of the target position is corrected with the calculated learning value, and the turbocharger is controlled.