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VVT-i, orVariable Valve Timing with intelligence, is anautomobilevariable valve timingpetrol enginetechnology manufactured byToyota Group and used bybrandsGroupe PSA (Peugeot andCitroen),Toyota,Lexus,Scion,Daihatsu,Subaru,Aston Martin,Pontiac andLotus Cars. It was introduced in 1995 with the2JZ-GE engine found in theJZS155 Toyota Crown andCrown Majesta.
VVT-i replaces the previousVVT system introduced in 1991 with the five-valve per cylinder4A-GE "Silver Top" engine found in theAE101 Corolla Levin andSprinter Trueno, which was a 2-stage hydraulically controlled cam phasing system. VVT-i varies the timing of theintakevalves by adjusting the relationship between thecamshaft drive (belt 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, includingVVTL-i,Dual VVT-i,VVT-iE,VVT-iW andValvematic have followed.Direct injection systems such as theD-4 (VVT-i D-4) andD-4S are also used in conjunction with VVT-i.
VVTL-i (Variable Valve Timing and Lift intelligent system) (also sometimes denoted as VVT-iL or Variable Valve Timing and Intelligence with Lift) is an enhanced version of VVT-i that can alter valvelift (andduration) as well as valve timing. It was introduced with the 16-valve2ZZ-GE engine found in the 1999Toyota Celica. The engine head resembles a typicalDOHC design, featuring separate cams for intake and exhaust with two intake and two exhaust valves (four total) per cylinder, but unlike a conventional design, each camshaft has two lobes per cylinder, one optimized for lower rpm operation and one optimized for high rpm operation, with higher lift and longer duration.[1] Each valve pair is 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 freely move up and down with the high lobe without affecting the rocker arm. When the engine is operating below 6,000–7,000 rpm (dependent on year, car, and ECU installed), the lower lobe is operating the rocker arm and thus the valves, and the slipper-follower is freewheeling next to the rocker arm. When the engine is operating above the lift engagement point, theECU activates an oil pressure switch which pushes a sliding pin under the slipper-follower on each rocker arm. The rocker arm is now locked into the slipper-follower's movements and thus follows the movement of the high rpm cam lobe and will operate with the high rpm cam profile until the pin is disengaged by the ECU. The lift system is similar in principle toHonda'sVTEC operation. Toyota has since ceased production of its VVTL-i engines in most markets because it does not meetEuro IV specifications for emissions regulations. This includes theCorolla T-Sport (Europe),Corolla Sportivo (Australia),Celica,Corolla XRS,Matrix XRS, and thePontiac Vibe GT, all of which had the2ZZ-GE engine fitted. On the other hand, theLotus Elise andExige continued to offer the2ZZ-GE engine until 2011, with the Exige also offering the engine with asupercharger.
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TheDual VVT-i system adjusts timing on both the intake and exhaust camshafts. It was introduced with theAltezza RS200's3S-GE engine in 1998. Dual VVT-i was later used in Toyota's 3.5-litre2GR-FE V6 engine, first appearing on the 2005Avalon. This engine can be found on numerous Toyota and Lexus models. By adjusting the valve timing, engine start and stop occurs almost unnoticeably at minimum compression. Fast heating of the catalytic converter to its light-off temperature is possible, thereby reducing hydrocarbon emissions considerably. Most Toyota engines including the1LR-GUE (V10, used in theLexus LFA),UR engines (V8),GR engines (V6),AR engines (largeI4),ZR engines (mediumI4), andNR engines (smallI4) use this technology.
VVT-iE (Variable Valve Timing - intelligent by Electric motor) is a version of Dual VVT-i that uses an electrically operated actuator to adjust and maintain intakecamshaft timing.[2] The exhaust camshaft timing is still controlled using a hydraulic actuator. This form of variable valve timing technology was developed initially forLexus vehicles. This system was introduced on the1UR-FSE engine in the 2007Lexus LS 460. The electric motor in the actuator spins in unison with the intake camshaft as the engine operates. To maintain camshaft timing, the actuator motor runs at the same speed as the camshaft. To advance the camshaft timing, the actuator motor rotates slightly faster than the camshaft speed. Conversely, to retard the camshaft timing, the actuator motor rotates slightly slower than the camshaft speed. The speed differences between the actuator motor and the camshaft is used to operate a mechanism that varies the camshaft timing. The advantage of electric actuation lies in its enhanced response and accuracy at low engine speeds and lower temperatures, as well as a greater total range of adjustment. The combination of these factors enables more precise control, resulting in improvements in fuel economy, engine output, and emissions performance.
VVT-iW (Variable Valve Timing - intelligent Wide) was introduced with the 2.0Lturbochargeddirect-injected8AR-FTS fitted to theLexus NX 200t. VVT-iW uses VVT-iW on the intake valves and VVT-i on the exhaust valves. The intake cam has mid-position cam lock mechanism that retards the continuously variable timing. It offers expanded valve opening angles (Wide) which enables the engine to operate in a modified-Atkinson cycle at low rpm for improved economy and lower emissions and in theOtto cycle at high rpm for better performance, while also delivering high torque throughout the entire rpm band.[3]
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TheValvematic system offers continuous adjustment to valve lift and timing and improvesfuel efficiency by controlling the fuel/air intake using valve control rather than conventional throttle plate control.[4] The technology made its first appearance in 2007 with the3ZR-FAE engine in theNoah[5] and later in early-2009 in theAvensis. This system is simpler in design compared toValvetronic andVVEL, allowing the cylinder head to remain at a similar height.
Since 1996, VVT-i is used in conjunction with Toyota'sgasoline direct injection (GDI) systems such as D-4 and D-4S. Toyota engines using direct injection systems are denoted with the "S" suffix in Toyota's engine naming scheme (e.g.2JZ-FSE,2GR-FSE and4U-GSE); this suffix was formerly used to denote engines with swirl intakes (e.g.3A-SU).
D-4 (Direct Four Line) is adirect injection system used in a number of Toyota engines, sometimes referred to asVVT-i D-4. Developed in 1996, it appeared as early as 2000 on the1JZ-FSE and2JZ-FSE engines found in some models of theToyota Crown andToyota Crown Majesta, and can also be found in several engines in theToyota Avensis andToyota RAV4. The D-4 system uses high-pressure swirl control valves to improvecombustion efficiency alongside a three-way catalytic converter. VVT-i is integral to the design of the D-4 system, and is used in conjunction with D-4 to offer ultra-lean fuel consumption with cleaner emissions without compromising performance. Power and torque outputs as well as engine responsiveness are also improved as a result. All D-4 engines use adrive by wire system for thethrottle body (also called anelectronic throttle control) instead of a mechanical linkage system via a throttle cable.[6]
D-4S (Direct Four Line Superior) is a twin injection fuel system that is an improved version of the previous D-4 system, combining both indirect and direct injection. It uses a traditional manifold fuel injector on one end for low pressure and a direct injector on the other for high pressure. It also works in conjunction with VVT-i (as well as its variants). This system debuted in the2GR-FSE engine used in theToyota Crown Athlete and theLexus IS 350, which was also the first engine overall to combine both traditional fuel injection with direct injection. This system was also used in the4U-GSE (FA20) engine found in the 2012–2021Toyota 86 andSubaru BRZ as well as theFA24D engine used in the 2022–presentToyota GR86 and Subaru BRZ, both working in conjunction with Subaru'sAVCS system. The D-4S system provides much more cleaner exhaust emissions than with D-4,[7] while also helping with providing more peak power at high rpms.
It is important to note that the "S" in the D-4S name doesnot signify asupercharged engine, as engines using the D-4S system such as the 4U-GSE and the 2GR-FSE do not have superchargers. Traditionally, supercharged engines are denoted as "Z" under Toyota's engine naming scheme (e.g.4A-GZE,1G-GZE and2TZ-FZE).
In 2010, Toyota USA announced aLimited Service Campaign (LSC 90K) to replace the rubber portion of the oil supply hose for the VVT-i actuator on the2GR-FE (V6) engine, which were found to be defective. In all, approximately 1.6 million vehicles manufactured prior to 2008 were affected. The defective oil supply hoses were prone to degradation and eventual rupture, causing oil to rapidly leak and resulting in permanent engine damage. In 2014, the LSC 90K Campaign was extended to 31 December 2021[8] on 117,500 Toyota brand vehicles that were "missed" during the initial campaign.
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