VVT-i

Cutaway view of Variable ValveTiming with intelligence on a ZRengine in Techniquest Glyndr

VVT-i, or Variable Valve Timing with intelligence,is an automobile variable valve timing technology devel-oped by Toyota. The Toyota VVT-i system replaces theToyota VVT oered starting in 1991 on the 5-valve percylinder 4A-GE engine. The VVT system is a 2-stage hy-draulically controlled cam phasing system.VVT-i, introduced in 1996, varies the timing of the intakevalves by adjusting the relationship between the camshaftdrive (belt, scissor-gear or chain) and intake camshaft.Engine oil pressure is applied to an actuator to adjust thecamshaft position. Adjustments in the overlap time be-tween the exhaust valve closing and intake valve open-ing result in improved engine eciency.[1] Variants of thesystem, including VVTL-i, Dual VVT-i, VVT-iE, andValvematic, have followed.

1 VVTL-iVVTL-i (Variable Valve Timing and Lift intelligent sys-tem) is an enhanced version of VVT-i that can alter valvelift (and duration) as well as valve timing. In the case ofthe 16 valve 2ZZ-GE, the engine head resembles a typi-cal DOHC design, featuring separate cams for intake andexhaust and featuring two intake and two exhaust valves(four total) per cylinder. Unlike a conventional design,each camshaft has two lobes per cylinder, one optimizedfor lower rpm operation and one optimized for high rpmoperation, with higher lift and longer duration. Each valvepair is controlled by one rocker arm, which is operatedby the camshaft. Each rocker arm has a slipper followermounted to the rocker arm with a spring, allowing the

The 2ZZ-GE engine, the rst to feature VVTL-i

slipper follower to freely move up and down with the highlobe without aecting the rocker arm. When the engineis operating below 6000-7000 rpm (dependent on year,car, and ECU installed), the lower lobe is operating therocker arm and thus the valves, and the slipper-followeris freewheeling next to the rocker arm. When the engineis operating above the lift engagement point, the ECU ac-tivates an oil pressure switch which pushes a sliding pinunder the slipper follower on each rocker arm. The rockerarm is now locked into slipper-followers movements andthus follows the movement of the high rpm cam lobe, andwill operate with the high rpm cam prole until the pinis disengaged by the ECU. The lift system is similar inprinciple to Honda VTEC operation.The system was rst used in 2000 Toyota Celica with2ZZ-GE. Toyota has now ceased production of itsVVTL-i engines for most markets, because the enginedoes not meet Euro IV specications for emissions. Asa result, this engine has been discontinued on some Toy-ota models, including that of the Corolla T-Sport (Eu-rope), Corolla Sportivo (Australia), Celica, Corolla XRS,Toyota Matrix XRS, and the Pontiac Vibe GT, all ofwhich had the 2ZZ-GE engine tted. The Lotus Elisecontinues to oer the 2ZZ-GE and the 1ZZ-FE engine,while the Exige oers the engine with a supercharger.The Toyota Yaris uses VVT-i on its gasoline engines.

2 Dual VVT-iThe Dual VVT-i system adjusts timing on both intakeand exhaust camshafts. It was rst introduced in 1998 on

1

2 7 REFERENCES

BEAMS 3S-GE 5th-generation engine (Black Top). The rst tobe tted with Dual VVT-i

the RS200 Altezzas 3S-GE engine.Dual VVT-i is also found in Toyotas new generation V6engine, the 3.5-liter 2GR-FE rst appearing on the 2005Avalon. This engine can now be found on numerous Toy-ota and Lexus models. By adjusting the valve timing,engine start and stop occurs almost unnoticeably at mini-mum compression. Fast heating of the catalytic converterto its light-o temperature is possible, thereby reducinghydrocarbon emissions considerably.Most Toyota engines including the LR engines (V10, usedin the Lexus LFA), UR engines (V8), GR engines (V6),AR engines (Large I4), and ZR engines (Small I4) nowuse this technology.

3 VVT-iE

The 1UR engine, the rst to feature VVT-iE

VVT-iE (Variable Valve Timing - intelligent by Electricmotor) is a version of Dual VVT-i that uses an electricallyoperated actuator to adjust and maintain intake camshafttiming.[2] The exhaust camshaft timing is still controlledusing a hydraulic actuator. This form of variable valvetiming technology was developed initially for Lexus ve-hicles. This system was rst introduced on the 2007MYLexus LS 460 as 1UR engine.

4 VVT-iWVVT-iW was introduced with the 2.0L turbochargeddirect-injected 8AR-FTS tted to the Lexus NX200t.It enables the engine to operate in both the Otto anda modied-Atkinson cycle, by oering expanded valveopening angles, resulting in increased fuel-eciency atlow engine loads.The electric motor in the actuator spins together with theintake camshaft as the engine runs. To maintain camshafttiming, the actuator motor will operate at the same speedas the camshaft. To advance the camshaft timing, the ac-tuator motor will rotate slightly faster than the camshaftspeed. To retard camshaft timing, the actuator motor willrotate slightly slower than camshaft speed. The speed dif-ference between the actuator motor and camshaft timingis used to operate a mechanism that varies the camshafttiming. The benet of the electric actuation is enhancedresponse and accuracy at low engine speeds and at lowertemperatures. as well as a greater total range of adjust-ment. The combination of these factors allows more pre-cise control, resulting in an improvement of both fueleconomy, engine output and emissions performance.

5 ValvematicThe Valvematic system oers continuous adjustment tolift volume and timing, and improves fuel eciency bycontrolling the fuel/air mixture using valve control ratherthan conventional throttle plate control.[3] The technol-ogy made its rst appearance in 2007 in the Noah[4] andlater in early-2009 in the ZR engine family used on theAvensis. This system is simpler in design compared toValvetronic and VVEL, allowing the cylinder head to re-main at the same height.

6 See also Variable valve timing Variable valve lift Gasoline Direct Injection (Toyota D4 and D4-S) Variable Length Intake Manifold List of Toyota engines

7 References[1] Variable Valve Timing Mechanism on Toyota.

YouTube. 2006-09-10. Retrieved 2009-06-29.

[2] Lexus LS engine page

3[3] Toyota Develops Next-generation Engine Valve Mecha-nism 'Valvematic' Achieves High Fuel Eciency andDynamic Performance ". TOYOTA. 2010-06-12. Re-trieved 2009-06-29.

[4] Nunez, Alex (2011-07-01). Toyota Noah / Voxy: Valve-matic for the people (movers)". Autoblog.com. Retrieved2009-06-29.

8 External links Youtube video: How VVT-i system works Toyotaengine

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

VVTL-i walkthrough VVTL-i ash animation

4 9 TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES

9 Text and image sources, contributors, and licenses9.1 Text

VVT-i Source: http://en.wikipedia.org/wiki/VVT-i?oldid=657308576 Contributors: The Anome, Morven, Sfoskett, Stocksy, Harriv,Hooperbloob, Interiot, Pethr, Firsfron, Guardian, Royan, BD2412, Ra*, Rjwilmsi, Feydey, FlaBot, WEKS, YurikBot, Malcolma,Ninly, 3sgte, GoneAwayNowAndRetired, Jacob Poon, OrphanBot, Stepho-wrs, Buttery0fdoom, Ariefwn, Jaganath, Imzjustplayin,Look4mathewkrom, Saad awal, Hu12, Emote, CmdrObot, Scirocco6, Cydebot, Arruah, Pinzvidz, Dogaroon, Dutchct, LG4761, Realarms,Oosh, Mr Grim Reaper, Husond, Magioladitis, Schatman, R'n'B, Clerks, Victuallers, STBotD, Andylong, DOHC Holiday, Wcrosbie,Anna Lincoln, Telecineguy, Andy Dingley, Poltair, Typ932, Regushee, Sfan00 IMG, ClueBot, Singhalawap, BOTarate, Aitias, 1dschock,XLinkBot, Fiskbil, MTan355, HexaChord, Addbot, Yobot, Ae86forlife, Backslash Forwardslash, AnomieBOT, DemocraticLuntz, Revela-tionDirect, GrouchoBot, Prari, T3h 1337 b0y, MastiBot, Moretrablo, Casamano, Gordido300, Jappahut12, Klampet32, Bdc101, ZroBot,ClueBot NG, Cabalaei3, ChrisGualtieri, Hittylili and Anonymous: 71

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VVTL-i Dual VVT-iVVT-iEVVT-iWValvematicSee also References External links Text and image sources, contributors, and licensesTextImagesContent license