How Variable Valve Timing Works?

The modern cars have all types of sensors and gadgets, and they also have a central computer system for the smooth operation. There are so many things going on under the hood, and you don’t even need to know the functions of half of these parts. However, if you are a car enthusiast, you should know about some important components, and the variable valve timing (VVT) is one of them.

Definition of Variable Valve Timing

The variable valve timing systems are seen in the internal combustion chamber of an engine. It does the job of changing the timing of a valve’s opening and closing and works together with the valve lift system.

This component is important because its proper use can enhance engine performance, increase fuel efficiency, and reduce emissions.

variable valve timing systems
A variable valve timing system. (photo source: Picasa)

The two-stroke engines don’t have a VVT, but they use power valve systems to produce same type of performances.

Important Parts of VVT

The entire VVT system and its components depend on the engine oil circulation. If there’s any problem with the oil flow, all the parts can fail permanently.

The two most important parts of this system are:


Each camshaft has a solenoid that works on the oil pressure to the camshaft. It can change the pressure based on the engine load and speed. It also helps to induce the right performance of the engine by enhancing or blocking the cam position.

This component can fail because of two reasons – irregular oil changing in the filters and engine, and low level of oil in the engine.

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Also known as cam phaser, this device does the job of maximizing torque curves and enhancing engine horsepower. It ensures that your car is getting the best performance from the engine while releasing less carbon footprint.

How Does Variable Valve Timing Work?

There are several valves to be found inside the combustion chamber on an engine. These are responsible for controlling the gas flow entering and exiting the combustion cylinder. Without a VVT, the timing of all the valves will be same for every engine condition and speed. It hampers the performance because the timing should be adjusting to these factors. A variable valve timing allows the changing of timing based on speed and engine condition.
There are two major types of VVT systems. Let’s have a look:

How Variable Valve Timing Works
A VVT in action. (photo source: philipus/123RF)

Cam Phasing

It rotates the camshaft over a range of 60 degrees to boost or check valve lift events. For example, a valve can open and close at 5 and 185 crankshaft degrees, respectively, before and after top dead center. If the valve timing restrains the lift events by 10 degrees, the valve will open and close at 10 degrees later, respectively. It will help the engine to produce better power at high RPM while advancing the timing will enhance the power at low RPM.

Cam Changing

It changes the angle of the camshaft phase to the crankshaft along with the shape of the camshaft lobes. These changes affect the opening of the valve and the duration it will stay open. Such alteration to the timing of the valves’ operation helps a vehicle to achieve its maximum efficiency.