Stable combustion to reduce fuel consumption - Details of VVT technology in Automobile Engine

Simple explanation:

The technology itself is not magic, but it has some of the effectiveness of dice. Its characteristics are to ensure that the combustion stability and reduce fuel consumption, effectively improve the emissions of hydrocarbons and nitrogen oxide, while expanding the volume efficiency and improve the combustion performance. Of course, the principle of VVT technology is actually very simple: As the engine needs different power at different times, VVT technology adjusts flow rate by adjusting the displacement of valve opening  and thus make the engine has a better working condition at different speeds:

1, delay the opening time of intake valve and reduce the valve angular overlap, can stabilize the combustion when in the idling state, decrease fuel consumption and lower pollution emissions when in medium operation condition(Uniform medium-speed traffic), and improve the working efficiency of the engine at a high speed;

2, move up the opening time of intake valve and increase valve angular overlap, can give greater torque when at low-speed and in high-load operation(starting, acceleration, climb)

In recent decades, based on the requirements, such as raising the automobile Dynamic Property, fuel economy, reducing emissions, many countries and engine manufacturers, scientific research institutions put in a lot of manpower and material resources to carry out research and development of new technologies. Currently, these new technologies and new methods, some of which have been applied in internal combustion engines, some are in the stage of development and improvement which has the potential to become the future direction of development of internal combustion engine technologies.

Engine variable valve timing technology(VVT) is one of the new technologies which has been gradually applied on the modern cars in recent years, it was developed by Giovanni Torazza in the late 1960s, the engine used variable valve timing technology to increase the intake charge, so to increase the volumetric efficiency and further raise the engine torque and power.

Today, as Honda's i-VTEC, Toyota's VVT-i etc, are derived from the VVT engine control technology.

Various manufacturers have very different VVT technologies, in common is the valve timing must be adjusted, so that the engine can have a different angular overlap between the intake valve and exhaust valve at different speeds, so as to improve those foregoing issues. To change the valve timing can be many different ways, but the most important categories can be reduced to two, one is to change the Camshaft Timing , and the other is to directly change in the shape of cam surface. Think about it, we know that change the shape of cam surface may not be easy? So the first category of VVT is easier to achieve.

If the VVTL-i, i-VTEC and VarioCam Plus is a blend of the first and second category of the VVT, then, the mode that Valvetronic uses in variable valve lift seems to be considered as the inventive third way. Are there others VVT? Yes. BMW engineers lay stress on adjustment of valve lift, Rover's engineers chose the valve opening time-history as a adjusted target. In Rover VVC, because of the cam can be driven by the unique designed eccentric wheel, the rotation is not uniform, as a result, valve opening time is also changing while adjusting the valve timing, although the valve lift does not change. VVC is a rather complex system, I have not seen the concrete structure diagram, and is not very clear about its specific principle, only know that it is usually just for regulating the intake valve and can be done to continuously change the intake valve timing and opening time-history. crazy Britain!

In another VVT system DC is developing, camshaft of engine is completely abandoned, each valve, or a number of valve movements are driven directly through the specific electromagnetic system, they act the way whatever ECU need, which is the highest level VVT technology pursues! Believe that all manufacturers have similar efforts!