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Discussion Starter #1
Can anyone please direct me to where I can learn the differences between VVT-i, VVTL-i, dual VVT-i, etc. and how each of them work in its own wonder?

Whats getting me is the dual VVT-i. What is so "dual" about it? Is there two points that VVT-i uses a different cam lobe? I have no clue. I need to learn! I appreciate any help, thanks.
 

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There's actually another called VVT.

Okay, here's the basic rundown of the four systems:

VVT - only had two settings (after a certain RPM, the cam timing changes) to control the timing of the intake valves (could be found in the 4A-GE 20V and the 3VZ-FE).

VVT-i - called "intelligent" because the system can "infinitely" adjust the timing of the intake valves over all RPM's. Found on nearly every Toyota engine.

Dual VVT-i - whereas VVT-i only acts on the intake valves, Dual VVT-i can also adjust the timing of the exhaust valves. Only found on the 3S-GE powering the Altezza RS200. This is similar to BMW's Double VANOS.

VVTL-i - another system that improves on VVT-i. In addition to infinitely controlling the timing of the intake valves, VVTL-i has a second cam profile that increases valve lift on both intake and exhaust valves. The change in valve lift occurs at 6000 or so RPM. Only found on the 2ZZ-GE that powers the Celica GT-S and JDM Corollas.

[ April 27, 2001: Message edited by: JW ]
 

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Discussion Starter #3
Thanks a lot but a question to clarify something. Does VVTL-i also adjust the timing of exhuast valves or does it only increase the exhuast's valve lift?

What engine technology, can you hypothesis, that will be next coming from Toyota?
 

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VVTL-i only controls the cam timing of the intake valves but can control the lifts of both intake and exhaust valves.
 

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Why in the world would they make a timing system that only adjusts the timing of the intake side? That's just half-assed! No one in their right mind buys cam gears (for example) and only adjusts the intake, you might as well not buy them at all!

Doesn't it make sense that to enjoy the benefits of earlier/longer fuel entry that you have to flush the old exhaust gasses out earlier/longer as well?

[ April 27, 2001: Message edited by: webguyIS ]
 

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Probably a cost issue...that's why I think Toyota should continue development of Dual VVT-i.
 

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The gains from adjusting intake valves are higher than adjusting the exhaust. Think about it, it's more difficult to get more air in the cylinder than out because the exhaust gasses are hot are a escaping very quickly because of thier need to expand. It makes sence to impliment a simple variable lift/duration system on the intake side only because it is cheaper to do this. Variable lift/duration on the exhaust side can be used to squeze the last bit of power out of the engine, but at a much higher price/complexity. Most of the Honda VTEC implimentations are intake only, the exceptions (off the top of my head) being the DOHC VTEC in the Civic-SI, NSX, and S2000.
 

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I can see how they might take cost into consideration and develop that single VVT-I for lower-end cars like maybe the Toyota Corrola or something (like the Civic EX) but I can't see why they would skimp on that for the Lexus or higher-end Toyotas (does the Celica have single VVTL-I as well?).

Left over exhaust gases take up valuable space in the combustion chamber, it's always best to get as much out as possible (even though it might not make as much difference as an intake adjustment would). I see yer point on that.

Disclaimer: I am not bitching about Lexus, I love the car and I will own one. Just curious... =)
 

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Thanks JW - you did a great job summarizing this technology!


I agree - they only used VVT-i mainly because of cost-benefit. Going to the dual VVT-i or VVTL-i tends to only help high RPM power, so they probably decided that VVT-i was enough (getting good low end torque) for our American driving habbits.

Also, (using the 2ZZ-GE Celica GTS engine as an example) the VVTL-i equipped cars need alot of other mods like high compression pistons, stronger valves, etc. Yamaha helped toyota out with the engineering on that VVTL-i 2ZZ-GE engine so I can see why Toyota wouldn't want to spend the money to pay Yamaha to re-engineer all of the engines.

That 2ZZ-GE VVTL-i engine is supposed to show up in more cars (like the new Vibe/Matrix all wheel drive mini sport ute), and (hopefully, crossing my fingers!) the MR2-Spyder.

If the bean counters at Toyota decide that they can make money with a car going for the M3 market then they could easily get 280hp+ out of the 2JZ-GE engine by going with dual VVT-i or VVTL-i... It is just a matter of deciding to spend the money and time to do the project.
 

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The Pontiac Vibe and Toyota Matrix actually borrow the Celica GT-S' engine. I didn't know any Corolla also had the same engine...thanks for the info!

By the way...VVTLi is GREAT! The switchover is dramatic and makes my heart race every time I hit it. But dang...Gotta respect the IS300's! Five gears compared to my 4
. Well, it's all about sportshift love, baby!
 

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Discussion Starter #16
Couldn't they use what they have learned during the making of the 2ZZ-GE and apply it to a 3.0L series? Perhaps it would not need Yamaha the second time around.
 
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