VVT-i Engine


VVT-i, or Variable Valve Timing with intelligence:-
                                                                                                                                       is an automobile variable valve timingtechnology developed by Toyota, similar in performance to the BMW's VANOS. The Toyota VVT-i system replaces the Toyota VVT offered starting in 1991 on the 5-valve per cylinder 4A-GE engine. The VVT system is a 2-stage hydraulically controlled cam phasing system.

VVT-i, introduced in 1996, varies the timing of the intake valves by adjusting the relationship between the camshaft drive (belt, scissor-gear 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. Variants of the system, including  Dual VVT-i.














File:Toyota 1ZZ-FE engine.jpg
Variable valve timing allows the relationship between the separate inlet and exhaust camshafts to vary the valve timing overlap. In doing so it overcomes the side effects described above by using a computer to continuously vary the intake valve timing and overlap. The valve timing and overlap are adjusted through a series of simple mechanisms to ensure the optimum conditions apply across all the working rev range. The advantages are lower fuel consumption, lower exhaust emissions and higher power output. Because the system is continuously variable, an ‘i’ for ‘intelligent’ has been added to the acronym.
how vvti engine works





Dual VVT-i :-
                                   in 1998, Dual VVT-i which adjusts timing on both intake and exhaust camshafts was first introduced on the RS200 Altezza's 3S-GE engine.

Dual VVT-i is also found in Toyota's new generation V6 engine, the 3.5-liter 2GR-FE first appearing on the 2005 Avalon. This engine can now be found on numerous Toyota and Lexus models. By adjusting the valve timing, engine start and stop occurs almost unnoticeably at minimum compression. In addition fast heating of the catalytic converter to its light-off temperature is possible thereby reducing hydrocarbon emissions considerably.

Toyota's UR engine V8 also uses this technology. Dual VVT-i was later introduced to Toyota's latest small 4-cylinder ZR engines found in compact vehicles such as the new Toyota Corolla and Scion xD and in larger 4-cylinder AR engines found in the Camry and RAV4.














In 1998, “Dual” VVT-i (adjusts both intake and exhaust camshafts) was first introduced in the RS200 Altezza’s 3S-GE engine. Dual VVT-i is also found in Toyota’s new generation V6 engine, the 3.5L 2GR-FE V6. This engine can be found in the Avalon, RAV4, and Camry in the US, the Aurion in Australia, and various models in Japan, including the Estima. Dual VVT-i is also used in the Toyota Corolla (1.6 dual VVT-i 124bhp).
Other Dual VVT-i engines include the 1.8L 2ZR-FE I4, used in Toyota’s next generation of compact vehicles such as the Scion XD. It is also used in the 2JZ-GE and 2JZ-GTE engines used in the Lexus IS300 and in the Toyota Supra. By adjusting the valve timing engine start and stop occurs virtually unnoticeably at minimum compression. In addition fast heating of the catalytic converter to its light-off temperature is possible thereby reducing hydrocarbon emissions considerably.


File:2GR-FSE.jpg