The document discusses Honda's i-VTEC (Variable Valve Timing and Lift Electronic Control) engine technology. It works by using two camshaft profiles and electronically selecting between them to improve engine efficiency. The basic mechanism uses a hydraulically actuated pin to switch between cam lobes. At low speeds it uses a low-lift cam profile for efficiency, switching to a high-lift profile for more power at higher speeds. i-VTEC provides benefits like better fuel efficiency and torque but also has limitations like increased costs and complexity.