VVT-i

VVT-i, orVariable Valve Timing with intelligence, යනුමෝටර් රථවලvariable valve timingතාක්ෂණයකි.ටොයොටාසමාගම විසින් දියුණුකල මෙ‍ම ක්‍රමය, similar in performance to the BMW'sVANOS.  The Toyota VVT-i system replaces the Toyota VVT offered starting in 1991 on the 5-valve per cylinder4A-GEengine.  The VVT system is a 2-stage hydraulically controlled cam phasing system.
VVT-i, introduced in 1996, varies the timing of theintakevalvesby adjusting the relationship between thecamshaftdrive (belt, scissor-gear or chain) and intakecamshaft.  Engine oil pressure is applied to an actuator to adjust the camshaft position.
Video animation of VVT-i (courtesy of PT. Toyota Astra Motor, Indonesia) can be found here[1].
In 1998, Toyota began offering a new technology,VVTL-i, which can alter valvelift(andduration) as well as valve timing.  In the case of the 16 valve2ZZ-GE, the engine has 2 camshafts, one operating intake valves and one operating exhaust valves.  Each camshaft has two lobes per cylinder, one low rpm lobe and one high rpm, high lift, long duration lobe.  Each cylinder has two intake valves and two exhaust valves.  Each set of two valves are controlled by one rocker arm, which is operated by the camshaft.  Each rocker arm has a slipper follower mounted to the rocker arm with a spring, allowing the slipper follower to move up and down with the high lobe without affecting the rocker arm.  When the engine is operating below 6000-7000 rpm (dependent on year, car, and ECU installed), the low lobe is operating the rocker arm and thus the valves.  When the engine is operating above the lift engagement point, theECUactivates an oil pressure switch which pushes a sliding pin under the slipper follower on each rocker arm.  This in effect, switches to the high lobe causing high lift and longer duration.
Toyota has now ceased production of its VVTL-i engines for most markets, because the engine does not meetEuro IVspecifications for emissions. As a result, this engine has been discontinued on some Toyota models, including that of theCorollaT-Sport (Europe),CorollaSportivo (Australia),Celica,Corolla XRS,Toyota MatrixXRS, and thePontiac VibeGT, all of which had the2ZZ-GEengine fitted.
TheLotus Elisecontinues to offer the2ZZ-GEand the1ZZ-FEengine, while the Lotus Exige offers the engine with asupercharger.
In 1998,Dual VVT-iwhich adjusts timing on both intake and exhaust camshafts was first on හදුන්වාදුන්  RS200 Altezza's3S-GEengine.
Dual VVT-i is also found in Toyota's new generation V6 engine, the 3.5-liter2GR-FEfirst appearing on the2005 Avalon. මේ engine can now be found on numerous Toyota and Lexus models. By adjusting the valve timing engine start and stop occurs virtually unnoticeable at minimum compression.  In addition fast heating of the catalytic converter to its light-off temperature is possible thereby reducing හ්ය්ද්රෝ කබන් emissions considerably.
Toyota'sUR engineV8 also use this technology. Dual VVT-i was later හදුන්වාදුන්  ටොයෝට's අළුත්ම පොඩි සිලින්ද්දර්-4ZR enginesfound in compact vehicles such as the අලුත් ටොයෝට  Corolla සහ Scion XD and in larger 4-cylinderAR enginesfound in the Camry and RAV4.
VVT-iEuses an විදුලි මෝටරය instead of hydraulic සැකසුම්  to control intake valve timing offering greater precision at අඩු rpms සහ උෂ්ණත්වයට.
Toyota first presented details about its latestValvematictechnology in June 2007.Valvematic made its first appearance in early-2009 in theZR engine familyused on theToyota Avensis.  This system is simpler in design compared to Valvetronic and VVEL, allowing the cylinder head to remain at the same height.
BWMValvetronic, NissanVVELand HondaA-VTEC.