Here's how the variable valve timing system works on your car:


Varying valve timing yields improvements in emissions, increases fuel economy and gains in power.
Here you can see the valve train - with the VVT actuator being the larger gear connected to the intake camshaft:



Here's a look underneath the engine head at the valves:



The VVT actuator is the heart of the system, using oil pressure built up inside chambers to rotate the output shaft relative to the input shaft, changing the phase angle:


See the small holes where oil travels into the chambers:


This is the solenoid the controls oil flow through the camshaft to actuate the timing gear in advance or retard: