Active valve control system
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Active Valve Control System (AVCS) is an automobile variable valve timing technology developed by Subaru. It varies the timing of the intake and exhaust valves by using hydraulic pressure to rotate the camshaft by up to 35 degrees. It is similar to Mazda's S-VT system.
The AVCS system is used in Subaru's WRX STi engine.
Another example is Honda's V-tec system, which also electronically controlls valve lift as well as adjusting timing. Honda were pioneers in this field.