What is vtec on Hondas and how does it work?

A proprietary variable valvetrain mechanism. It basically increases the lift and duration of the intake valves when the engine exceeds 5000rpm in most Hondas. This allows it to maximize top-end power and torque while maintaining low end torque and a smooth idle, where most high-lift fixed camshafts will cause a rough (lopey) idle, and poor low-rpm performance.

IT is a sophisticated system whereby the INTAKE and EXHAUST VALVES POSTIONS can be altered by computer control to various timing degrees to allow MORE power aND ECONoMY under various loads. It makes betteR FUEL MILES< and more power on demand. Most LATER model engines HAVE this feature with DIFFERENT names, like variable valve timing AND SUCH. IMPROPER OIL USE and oil neglect will RUIN these engines, or any other VARIABBLE TIMING engines, and only the BEST oils whoudl be used in them as these CHANGES in timing are based upon GOOD OIL FLOW and hydraulic actuators and such. GOOD LUCK!

Variable Timing Electronic Control

How it works, I don't know.