Method and system for controlling continuously variable valve timing

A system for controlling continuously variable valve timing (CVVT), the system comprising:

• a cam sensor configured to detect a position of a cam;
• a crank sensor configured to detect a position of a crankshaft;
• a CVVT apparatus provided with an oil control valve and an oil temperature sensor;
• an engine electronic control apparatus (ECU) configured to control an engine;
• and
• a CVVT controller configured to:
• determine whether a CVVT control is started;
• detect a position of a cam by a cam sensor and a position of a crankshaft by a crank sensor when the CVVT control is started;
• determine whether the cam is positioned at a locking position based on the position of the cam and the position of the crankshaft;
• determine whether the cam is controlled to be positioned from the locking position to an advancing position or a holding position, when the cam is positioned at the locking position;
• and
• when the cam is controlled to be positioned from the locking position to the advancing position or the holding position and when a condition for performing the CVVT control is satisfied, determine whether a cam torque is negative, and performing predetermined CVVT control after waiting a predetermined time when the cam torque is negative.