The Intelligence-Active Valve Lift System (i-AVLS) is a valvetrain technology implemented by Subaru in their 2.5 L SOHC naturally aspirated engine to improve emissions, efficiency and performance.
AVLS improves performance and efficiency by changing which camshaft is operating which of the two intake valves.
The camshafts on all AVLS Subaru engines have specially designed lobes for intake valves.
To select different valve lift modes, oil pressure generated by the engine moves a pin which locks the two lobes together.
At higher engine speeds the high lift camshafts fully open the intake valves, reducing resistance to incoming air and improving power.