The Toyota’s VVT – I system replaces the Toyota VVT which was started in offering in 1991 on the 5 – valve per cylinder 4A – GE engine. The VVT system is a 2 – stage cam phasing system which is hydraulically controlled.
VVT – I was introduced in 1996 and it varies the timing of the ingestion valves by adjusting the relationship linking the camshaft drive (chain, belt or scissor – gear) and ingestion camshaft. Engine oil pressure is applied to the actuator so as to alter the camshaft position. Adjustments in the partly cover time between the exhaust valve closing and ingestion valve opening which result in improved engine efficiency. Variants of this system include VVTL – I, Dual VVT – I, VVT – iE and Valvematic which follow configurations of VVT – I. Based on the VVT – I system, the VVTL – I system adopted a cam change over mechanism which vary the amount of lift of the intake and exhaust valves at the same time as the engine is operating at high speeds.
The Dual VVT – I system fuddles with timing on both intake and exhaust camshafts. In RS200 Altezza's 3S-GE engine, the dual VVT – I engine was first introduced. Dual VVT – I is too found in the Toyota's next generation V6 engine (the 3.5-liter 2GR-FE first seen on the 2005 Avalon). Numerous Toyota and Lexus models have been fitted with this engine now – a – days. By regulating the valve timing, the engine start and stop occurs almost imperceptibly at minimum compression. Fast heating of the catalytic converter to its light – off temperature might be expected, thus, sinking hydrocarbon emissions considerably. Most Toyota engines like the ZR engines (Small I4), AR engines (Large I4), GR engines (V6), UR engines (V8) and LR engines (The V10 used in the Lexus LFA) now use this technology.