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
||-10 to 33°
||58 to 15°
||124 - 81°
||15 to 58°
||97 to 54°
||131 - 88°
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.
to the VVT Vs V-TEC page
Back to details on the Honda S2000 engine
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