The engine is an energy conversion device that converts the thermal energy of gasoline (diesel) into mechanical energy by burning the expanded gas in a sealed cylinder, pushing the piston to do work. A machine that can convert other forms of energy into mechanical energy, including internal combustion engines, external combustion engines, electric motors, etc. Internal combustion engines usually convert chemical energy into mechanical energy. The engine is suitable for both power generation devices and the entire machine including the power device.

The most common engine parameter - engine displacement. The engine displacement is the sum of the working volumes of each cylinder in the engine, usually expressed in liters (L). The working volume of a cylinder refers to the volume of gas swept by the piston from top dead center to bottom dead center, also known as the single cylinder displacement, which depends on the cylinder diameter and piston stroke. The engine displacement is a very important engine parameter, which better represents the size of the engine than the cylinder diameter and number of cylinders. Many indicators of the engine are closely related to the exhaust volume. Generally speaking, the larger the displacement, the greater the output power of the engine. After understanding the displacement, let's take a look at other common engine parameters. Many beginner car enthusiasts often see words such as "L4", "V6", "V8", "W12" in the engine section of their car literature, hoping to understand what they mean. These all represent the arrangement and number of engine cylinders. The commonly used cylinder numbers for automotive engines include 3, 4, 6, 8, 10, 12, etc.

最常见的一个发动机参数——发动机排量。发动机排量是发动机各汽缸工作容积的总和，一般用升（L）表示。而汽缸工作容积则是指活塞从上止点到下止点所扫过的气体容积，又称为单缸排量，它取决于缸径和活塞行程。发动机排量是非常重要的发动机参数，它比缸径和缸数更能代表发动机的大小，发动机的许多指标都同排气量密切相关。一般来说，排量越大，发动机输出功率越大。了解了排量，再来看发动机的其他常见参数。很多初级车友都反映经常在汽车资料的发动机一栏中见到“L4”、“V6”、“V8”、“W12”等字样，想弄明白究竟是什么意思。这些都表示发动机汽缸的排列形式和缸数。汽车发动机常用缸数有3缸、4缸、6缸、8缸、10缸、12缸等。