Variable Valve Timing

Variable Valve Timing, or VVT, is the act of changing the valve timing, or the points at which the cylinder valves in an engine open and close; it may also involve changing the duration, the amount of time a valve is open, and/or the lift, the distance which the valve rises (and thus the speed at which air enters the engine.) Various systems perform some combination of changing timing, duration, or both. VVT systems may also control lift, or the distance the valve travels. Optimally, you would be able to change all of these values arbitrarily over time, as an engine behaves very differently at high RPMs than it does at idle or while cruising. Variable Valve Timing allows you to vary your valve timing to a certain degree, achieving significantly better efficiency at all speeds.


A thermostat works because of "unequal expansion of different metals, liquids, or gases by heat"1. Your car's thermostat is no different. It typically uses wax as the agent to operate the heat motor, or the part of the thermostat which converts heat into work - in this case, linear motion.

Timing Light

A timing light is a flashing light used to adjust the ignition timing advance on an automobile by means of markings on the crank pulley and on (or near) the engine block. It accomplishes this by flashing a light every time the number 1 spark plug fires. There are two kinds of Timing Light; inline, and inductive. Inline timing lights are connected by unplugging the #1 spark plug wire and plugging a connector inline (hence the name) with that wire. Inductive timing lights have a clip with an inductive sensor built into it, and are simply clipped around the spark plug wire. They will not work with coil on plug ignition, and some of the cheaper and/or older models will not work on distributor-free ("DFI") ignition systems, or some of the lower-power electronically controlled ignition systems. They also do not work on diesel engines.

Timing Advance

In a gasoline-powered internal combustion engine, an air/fuel mixture is drawn into the cylinder through the valves by the motion of the piston, and ignited by the spark plug. The easy assumption is that the mixture should be ignite|ignited when the cylinder reaches the top of its travel so that the resulting expansion of gases can force the cylinder down. However, it takes some time for ignition to occur.


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