vvt (part 1)

variable timing camshaft with solenoid

Engines have a low volumetric efficiency at high speed. As intake valves are opened at a much shorter time during high speed operation therefore causing lesser time for the air fuel mixture to enter the cylinders. If intake valves opened earlier at high speed, air fuel mixture will be able to to enter the cylinder, so more would get in.
One way to open the intake valves at an earlier period on high speed is to use variable valve timing camshaft.
It has a flexible connection between the camshaft sprocket and camshaft. The connection includes a a hydraulic piston operated by engine oil pressure and a solenoid operated control valve.When the ECU sends a signal to the solenoid to close the valve, the oil pressure forces the piston down towards the camshaft. as the piston moves,the internal teeth of the piston slide up the inclined teeth on the helical drive gear. this moves the camshaft ahead and advances camshaft timing to about 10 degrees. thus making the intake valves open earlier.