VVT-i

VVT-i, or Variable Valve Timing with intelligence, යනු මෝටර් රථවල  variable valve timing තාක්ෂණයකි.  ටොයොටා සමාගම විසින් දියුණුකල මෙ‍ම ක්‍රමය, 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.

Video animation of VVT-i (courtesy of PT. Toyota Astra Motor, Indonesia) can be found here .

VVTL-i  
In 1998, Toyota began offering a new technology, VVTL-i, which can alter valve lift (and duration) as well as valve timing.  In the case of the 16 valve 2ZZ-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, the ECU activates 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 meet Euro IV specifications for emissions. As a result, this engine has been discontinued on some Toyota models, including that of the Corolla T-Sport (Europe), Corolla Sportivo (Australia), Celica, Corolla XRS, Toyota Matrix XRS, and the Pontiac Vibe GT, all of which had the 2ZZ-GE engine fitted. 

The Lotus Elise continues to offer the 2ZZ-GE and the 1ZZ-FE engine, while the Lotus Exige offers the engine with a supercharger.

Dual VVT-i
In 1998, Dual VVT-i which adjusts timing on both intake and exhaust camshafts was first on හදුන්වාදුන්  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. 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's UR engine V8 also use this technology. Dual VVT-i was later හදුන්වාදුන්  ටොයෝට's අළුත්ම පොඩි සිලින්ද්දර්-4 ZR engines found in compact vehicles such as the අලුත් ටොයෝට  Corolla සහ Scion XD and in larger 4-cylinder AR engines found in the Camry and RAV4.

VVT-iE uses an විදුලි මෝටරය instead of hydraulic සැකසුම්  to control intake valve timing offering greater precision at අඩු rpms සහ උෂ්ණත්වයට.

Valvematic
Toyota first presented details about its latest Valvematic technology in June 2007. Valvematic made its first appearance in early-2009 in the ZR engine family used on the Toyota Avensis.  This system is simpler in design compared to Valvetronic and VVEL, allowing the cylinder head to remain at the same height.

Similar technology
BWM Valvetronic, Nissan VVEL and Honda A-VTEC.

See also 
 Variable valve timing
 Lexus VVT-iE
 Gasoline Direct Injection
 Variable Length Intake Manifold
 List of Toyota engines

References

External links 
 VVT-i video animation

ටොයොටා
මෝටර් රථ තාක්ෂණය