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Toyota VVTL-i Variable Valve Timing & Lift - Intelligent

The latest Toyota system, VVTL-i, ends up working in much the same fashion as the Honda V-Tec in that it uses a mechanical device to swap over between a 'small' cam for low & medium revs and a 'big' cam for high revs.
Since the effects of a system like this are well described in the previous pages, I won't go over that again, but I will talk briefly about how it works, and it will be a brief talk as it's a very simple device.

This is the VVTL-i in the low/medium rev setting. The small cam lobe runs on a small follower which itself is a part of a 'U' shaped device that operates both valves. The big cam runs on its own follower, but that follower has nothing to work against .... at the moment.

The device has now swapped over to high rev operation, and if you look at the right hand diagram you can see how hydraulic pressure has moved a small pin under the big cam's follower, thus making the connection and so making the valves follow the big cam's profile.

This system is fitted to the latest 1ZZ-FE & 2ZZ-GE engines, which make just over 100hp per litre.

Here's the system, as installed in the engine. It actually shifts both cam's timing & duration by changing lobes, as shown below

The VVT-i controller is on the inlet cam side, and on the inlet it works just like the 'old' VVT system, to alter the cam timing. The increased lift and second lobe itself is activated by the rest of the hydraulic system

And above is how the hydraulic system works to control the oil flow. It seems to have oil pressure available all the time, but only when the 'oil control valve' shuts off the oil drain-back does the oil pressure work to make the VVTL-i system go to the high rev position. When the valve is open, the oil flows under low pressure but high speed through the system

And finally above is a slightly better diagram of the VVTL-i follower system - you can see the ball-bearing roller in the low/medium rpm side of the follower, and the plain ramp version for the high rpm on the other. If you look carefully you can also see the third valve spring, for the high rpm operation, in the high speed follower section.

	Exhaust					Inlet
	Open BBDC	Close ATDC	Duration	Lobe centre	Lift (mm)	Open BTDC	Close ABDC	Duration	Lobe centre	Lift (mm)
Low RPM	34°	14°	228°	110°	7.6	-10 to 33°	58 to 15°	228°	124 - 81°	7.6
High RPM	56°	40°	276°	108°	10.0	15 to 58°	97 to 54°	292°	131 - 88°	11.2

The cam timing can vary quite a lot with the VVTL-i system, and above are the factory specifications for both cams of the 2ZZ-GE engine.

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