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Discussion Starter #1 (Edited by Moderator)
The Toyota VVTL-i system or "lift" is similar to Honda's VTEC system, incorporating two distinct cam profiles. However, the actual mechanism is quite different. Both cam lobes operate a single wide rocker arm that acts on both intake or both exhaust valves. A needle-bearing roller on the arm follows the low-rpm, short-duration, low-lift lobe, forcing both valves to open and close on that profile. The roller design and roller bearings on the rocker arm pivot help to minimize valvetrain friction. The high-rpm, higher-duration, longer-lift lobe rubs on a hardened steel slipper follower mounted to the rocker arm with a spring. Even though the high-rpm lobe is pushing down further than the low-rpm lobe, the spring absorbs the extra movement. At 6000rpm, the ECU sends a signal to an oil control valve at the end of the camshaft that puts oil pressure behind a lock pin in the rocker arm, sliding the pin under the spring-loaded slipper follower, locking it to the rocker arm and forcing the arm to follow the high-rpm cam profile. Below is an animation. you can actually see what im talking about lol.


i really dont know how else to explain how lift works. if anyone else anything else to add please do so. btw the source was from old sport compact issue that just completely fell apart. sticky this please.

and one more thing from dennis aka pioneer_sti http://web.newsguy.com/gtfour/misc/Chap8_vvti_and_acis.pdf
^pdf breakdown of vvtli. very good info in this link and pictures with what parts exactly are if you dont know. thanks dennis :wiggle:
 

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Excellent thread! My mom and I were talking about this yesterday! She had a formula firebird and used to work on her engine all the time :)

Kristin
 

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VVT-i, or Variable Valve Timing with Intelligence, is an automobile variable valve timing technology developed by Toyota. The latest version of VVT-i varies the timing of the intake valves by adjusting the timing chain connecting the intake and exhaust camshafts. A pump applies hydraulic pressure to adjust the gear driving the timing chain.

Toyota recently started offering a new technology, VVTL-i, which can alter valve lift (and duration) as well as valve timing. This is accomplished differently than Honda's VTEC. Instead of switching between two different cam shafts, there are spacers that are slid between a single cam shaft and the valves. At higher RPM, controlled by the ECU, oil pressure is directed to push the spacers between the camshaft lobes and valves, effectively simulating a much "hotter cam" and creating increased valve lift. When the engine falls in RPM the spacers are pulled out of action and the engine operates more economically. This system is used in the Yamaha designed 1.8 liter 4 cylinder 2ZZ-GE which is used in the Toyota Celica GT-S, Toyota Corolla XRS and Lotus Elise 111R. This variable lift technology allows the engine to be quite fuel efficient at lower RPMs and, when called upon, able to produce much more power at the expense of fuel economy.

For 2006, the company will add dual VVT-i, which varies timing independently on both the intake and exhaust cams. This will debut on the 2006 Toyota Avalon's 2GR-FE V6.
- wikipedia.org <3
 

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Lift!

This is the best description of lift I have ever encountered. The animation is sweet. I have had people try to explain this to me before, and Im like "ok, so it's like an internal turbo?". Thanks for the post. Im clear now.
 

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Discussion Starter #12
TRDHellica said:
what happend if the vvtl-i kickes in at arroung 7-7.5k rpm??
that means somethings wrong buddy. lift should kick in at 6.2k or 6k depending on which model gts you have. check your lift bolts, hopefulle thats it and that would be a easy fix.
 

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You know I thought my lift kicked in at 7K too. I just had my Direct clutch line installed and they had to take off my CAi to do it... I know it had nothing to do with lift but now my lift kicks in at about 6.5. Isn't that wierd????
 

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in the explanation it says "normal lift and duration". Just wondering at what rpms the normal lift and duration happens in our celica. My gfs corolla has vvti and i think, im not sure, i can feel something at around 4500rpm.
 

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importfreak8 said:
At 6000rpm, the ECU sends a signal to an oil control valve at the end of the camshaft that puts oil pressure behind a lock pin in the rocker arm, sliding the pin under the spring-loaded slipper follower, locking it to the rocker arm and forcing the arm to follow the high-rpm cam profile.
GF's car won't do lift unless it is an XRS. On a straight VVTi... you may see the slight change @ 4K RPM when the butterfly valve on the intake opens up.
 
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