VVT-i:-                         VVT-i  or   Variable Valve Timing with intelligence , is an automobile variable timing   technology developed by  Toyota .  The Toyota VVT-I system replaces the Toyota VVT  offered starting the age of 1991 on the 5 valve per cylinder 4A-GE Engine. The VVT system is the 2 stage hydraulically control phasing system.         VVT-i, introduced on the  Toyota JZ engine  in 1996, varies the timing of the  intake valve  by adjusting the relationship between the  camshaft  drive (belt or chain) and intake camshaft. Engine oil pressure is applied to an actuator to adjust the camshaft position. Adjustments in the overlap time between the exhaust valve closing and intake valve opening result in improved engine efficiency.     i-VTEC:-                i-VTEC or   ( Intelligence Variable Valve Timing and Lift Electronic Control ) is a system developed b...