VVTI

http://en.wikipedia.org/wiki/VVT-i

If you don't understand this, you'll need to learn how a 4 cycle engine works and how the valves on the engine acn be designed to optimize fuel economy, power, metalluraical design limits.

Then when you are proficient, look at the VVTL-i, I run one of these babies.

Try www.vvti.net. This is Toyota's main website for info.

vvti.net is not from Toyota. Its a Toyota car club forum. It does contain info but Toyota doesn't run the site.

Valves in a standard car engine let the air in and the exhaust out. They are driven buy a camshaft turned by the engine which is a set shape and so the valve movement occurs in a set pattern/timing. This shape, like most items on a car engine, is a compromise between low down grunt/fuel economy and high rev power/low 0-60mph times.

In recent years more complex engine designs try to provide the best of both worlds. One of these systems is VVTi which varies the timing of the camshaft movement depending on engine revs.

In general these systems depend on correct oil pressure and vicosity. More than ever do yourself and the engine a favour, if you do nothing else change the oil and filter regularly and 'save a da money'.