Who can help me explain the working principles and differences of CVVT, VVT-I, DVVT and VTEC in detail?

With regard to variable timing valve technology, different brands have different names and the basic principles are similar. Hyundai and Geely are called CVVT, Toyota is called VVTI, Honda is called IVTEC, Nissan is called CVTC, Mitsubishi is called MIVEC, Mazda is called S-VT and so on. This technology was first developed by Alfa Romeo, followed by Honda, and then began to see more.

The valve timing of the engine depends on the rotation angle of the camshaft. In an ordinary engine, the opening and closing time of intake valve and exhaust valve is fixed, so it is difficult to meet the working requirements of different engine speeds. In order to make the engine get higher efficiency, the opening and closing time of throttle can be changed by changing the inclination angle of camshaft, and variable valve timing technology is the technology to solve this problem.

Continuous variable valve timing and discontinuous variable valve timing are different, so we should pay special attention to this when choosing. Simple variable valve timing has only two or three fixed phase angles to choose from. The variable valve timing vvt system with higher performance can continuously change the phase angle, and the continuous variable valve timing system is more suitable for matching various speeds according to different speeds, thus effectively improving the output performance of the engine, especially the output ride comfort of the engine.

Generally speaking, this technology is to improve the air intake efficiency (now dual variables can also change the exhaust efficiency), get extra air, and then burn the corresponding extra oil, so as to achieve the purpose of high power output per unit displacement, emission reduction and fuel saving.