Advanced VTEC is a system designed to allow the variation of valve timing and lift. It is designed to improve engine Fuel efficiency without sacrificing performance. It is an evolution of a long line of VTEC systems from Honda.
Differences from other VTECs
Honda's advanced VTEC technology departs greatly from its previous incarnations by no longer relying on switching between two sets of lobes on a given camshaft. It instead uses a single cam lobe per valve, and two rocker arms per valve whereby the second rocker arm has a movable pivot point, there by provide the varying cam lift. Advanced VTEC motors still use the now standard oil pressure controlled variable cam gear angle mechanism. With these two technologies combined Honda has developed an infinitely variable valve timing and lift system ("VVTL"). Previous versions of VTEC included only staged VVTL i.e. High-Low. With the introduction of i-VTEC the systems gained infinitely variable valve timing but still only staged lift i.e. High-Low. The "infinitely variable" portion of the A-VTEC is what makes it stand out as a serious evolutionary step in the world of VTEC.
Explanation of patent
Advanced VTEC has a standard camshaft and rocker arms, attached as they normally are with camshaft overhead, and rocker arms pushing down on the poppet valves. The camshaft is surrounded by a partially open drum which has secondary rocker arms attached to it via a pivoting point. These secondary rocker arms, which have a varying depth profile (similar to cams), are directly actuated by the camshaft, in a scissor-like manner. The primary rocker arms are actuated by the secondary (drum attached) rocker arms. The drum will only rotate to advance or retard the position of the secondary rocker arms, to take advantage of their varying profiles. Thus, through varying the position of the drum about its axis, each cam profile is changed to an optimal height for maximum engine performance without sacrificing fuel efficiency at lower speeds.