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Discussion Starter #1
I am new to my celica and just wanted you guys to give me a technical but straightforward explanation of how vvtl-i works.

I would also like to know what sorta comprise has to be taken into consideration when running turbo along with vvtl-i , I am thinking that the air/gas mixture will be richer and hence have some effect on the stock configuration of this system.
 

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VVTL- i is a combination of two systems:

Variable Valve Timing with Intelligence varies the timing of the intake and (I think) exhaust valves to provide the best and most efficient power output given the current situation of the engine (RPMs, oil pressure, and other factors determine how the VVT-i works).

-and-

Lift: reflects that the valvetrain has two sets of cam profiles for the intake cam. Lift engages around 6000 rpm (the actual engaugement point depends on your model year). When lift is active, the second cam profile is operating, allowing the intake cams to let more air into the combustion chamber, making more power.

When it comes to both of these systems an forced induction (super or turbo charging) a new ECU is needed to allow the rest of the engine systems to work properly with the new abundance of air and fuel. Any turbo kit sold (any good kit) will include any engine management electionics needed.
 

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Discussion Starter #4
any diagrams with details?
 

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Discussion Starter #9
does vvtl-i sacrifice speed for fuel economy?...this is what I have been told.
 

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Originally posted by krichards
does vvtl-i sacrifice speed for fuel economy?...this is what I have been told.
No. The VVTLI once in lift is operating at full potential. Fuel economy was not a concern when lift was designed. If you ride the car in lift alot you will see that gas crumbles like Oscar in my sig.
 

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Zettai Unmei Mokushiroku
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Originally posted by krichards
does vvtl-i sacrifice speed for fuel economy?...this is what I have been told.
VVT-i can switch between economy and power mode, so it's the best of both worlds. Lift is just for power, and allows the engine to make power in higher RPMs, where it also uses more fuel. ;) Otherwise, the limiter would be at 6800-7000 like a GT, since the engine would be losing power rather quickly.
 

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The actual variable timing and lift technology was pioneered in an effort to increase fuel mileage and efficiency, while also getting more power. If you stay out of lift (below 6K--not hard), your mileage will be very decent.


Jon
 

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i never said there were... but the animation shows the rocker shaft and the oil that must pass through it in order to move the pins under the rocker arms...
R
 

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First off, here is a great link that talks about different aspects of how cars work.

http://autozine.kyul.net/technical_school/tech_index.htm

Anyways, for how VVTL-i works... the lift portion.

You have a camshaft with two lobes on it. A smaller one for normal RPM and a second one for when you hit 6000 RPM and you go into "lift". Note that the larger lobe, when used will push the valve open further.

Both lobes are attached hard to the camshaft and spin with every revolution. However, the larger lobe basically is set on a slipper so that its larger push is simply negated. Since the larger lobe is essentially doing nothing, the smaller lobe is what moves the rocker arm which pushes the valve open.

At high RPM, a hydraulic fluid pushes a pin under the larger lobe's slipper and thereby makes the rocker move with the larger lobe, thus pushing the valves open further and putting the engine into "lift".

Hope it helps.

W
 
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