一般来说，同等排量情况下，气门越多，进排气效率越好，就像一个人跑步，累得气喘吁吁时，需要张大嘴巴呼吸。传统的发动机多是每个气缸一个进气门和一个排气门，这种二气门配气机构相对比较简单，制造成本低，维修起来也相对容易。对于输出功率要求不太高的普通发动机来说，两气门就能获得较为满意的发动机输出功率与扭矩性能。
Generally speaking, the same displacement situations, the more the valve, inlet and exhaust efficiency, the better, like a man running, tired panting, need to open mouth breathing. More than the traditional engine is an inlet valve for each cylinder and an exhaust valve, the two valve distribution mechanism is relatively simple, low manufacturing cost, maintenance is also relatively easy. For ordinary engine output power requirement is too high, the valve can get more satisfactory engine power output and torque performance.
排量较大、功率较大的发动机要采用多气门技术。最简单的多气门技术是三气门结构，即在一进一排的二气门结构基础上再加上一个进气门。世界各大汽车公司新开发的轿车大多采用四气门结构。四气门配气机构中，每个气缸各有两个进气门和两个排气门。
Displacement is larger, the power of the larger engine more valve technology must be used. The simplest valve technology is more three valve structure, namely the one into a row of two valve structure based on coupled with an inlet valve. The world's largest car company newly developed cars mostly adopted four valve structure. Four valve of valve-train, each cylinder has two inlet valve and the exhaust valve.
四气门结构能大幅度提高发动机的吸气、排气效率，新款轿车大都采用四气门技术。当然，大众汽车多采用五气门技术，如老款捷达王的20V发动机，宝来1.8T发动机也是五气门。
Four valve structure can greatly improve the efficiency of the suction, exhaust of engine, the new cars are mostly adopted four valve technology. Volkswagen more, of course, take five valve technology, such as old 20 v engine, jetta baolai 1.8 T engine is five valve.
不过，达到或超过六气门不仅使配气结构过于复杂，还会导致发动机寿命缩短，气门开启的空间帘区(气门的圆周和气门的升程)也较小，效率下降。因此，四气门技术目前使用最为普遍。
However, reach or exceed six valve not only makes the distribution structure is too complex, can also lead to shorten the life engine, the valve open space of the shade area (the circumference of the valve and valve lift) is small, efficiency is decreased. Therefore, four valve technology currently in use is most common.
需要指出的是，气缸和气门数可以作为判断发动机优劣的标准之一，但不是唯一标准。比如，宝马公司的直列4气缸2.0升发动机，由于其独特的可变气门技术，在功率和扭矩输出上丝毫不逊于普通的6缸机，这也是宝马318轿车动力性广受好评的原因。奔驰公司长期采用每个气缸3气门技术，也达到了很好的功率、扭矩和环保水平。此外，配备涡轮增压技术后，宝来1.8T4缸机的功率和扭矩也能达到普通6缸机的水平。
It should be pointed out that, number of cylinders and valves can be used as one of the advantages and disadvantages of standard judgment of engine, but it is not the only standard. For instance, BMW's 2.0 -liter inline 4 cylinder engine, because of its unique variable valve technology, on the power and torque output is no worse than the ordinary 6 cylinder machine, this is why BMW 318 sedan performance critically acclaimed. Mercedes with 3 valves per cylinder technique for a long time, also reached the good power, torque and the environmental protection level. In addition, equipped with a turbo technology, baolai 1.8 T4 cylinder machine power and torque can reach common six-cylinder machine level.
