Classification of Reciprocating Internal Combustion Engines

What are the characteristics of piston internal combustion engines?
Reciprocating internal combustion engines are classified according to such criteria. By the way the workflow is carried out - on engines with external mixture formation (carburetor and gas) and internal mixture formation (diesel).

By the method of ignition of a combustible mixture - on engines with forced ignition (carburetor and gas) and self-ignition (diesel). In carburetor and gas engines, a combustible mixture is ignited by an electric spark generated by an ignition system. In diesel engines, the combustible mixture spontaneously ignites due to the high temperature that occurs when air is compressed in the engine cylinder.

By the number of clock cycles, the engines are divided into two- and four-stroke. By the type of fuel used - for engines of light or light fuel (gasoline, alcohols), heavy fuel (diesel fuel, diesel oil, oil) and gaseous fuel engines (methane, hydrogen, propane-butane mixtures).

By the number of cylinders - for single-cylinder and multi-cylinder. By the arrangement of the cylinders - on vertical (single row), V-shaped (double row) and horizontal (opposed). In the boxer engine, the angle between the cylinders is 180 °. By type of cooling - for engines with liquid and air cooling. In terms of displacement (displacement), engines are divided into small displacement engines with a displacement of up to 1.2 l, small displacement (from 1.2 to 1.8 l), medium displacement (from 1.8 to 3.5 l) and large displacement (over 3.5 l).

Depending on what factors is the engine selected?

The acceptance of a particular engine for installation on a vehicle depends on the type of vehicle on which it is to be installed, its purpose, load capacity, and speed.

Types of piston internal combustion engines

Automakers are developing more and more new engines every year. They differ in size, volume and power.

The range of engines installed on a particular car, replete with an assortment. For one model, the manufacturer can offer up to 15 engine options. The type of fuel, horsepower, the number of cylinders, the presence of a turbine, the type of injection, the number of valves - distinguish motors from each other. But one of the most important criteria for distinguishing engines is their type. It is he who is most often marked with an additional nameplate on the trunk lid. Internal combustion engines (ICE) can be divided into in-line, V-shaped, VR-shaped, box-shaped and W-shaped. They also include a rotary motor. Auto Informant figured out what are the characteristic differences between these internal combustion engines.

Briefly about the principle of operation of the most common four-stroke piston internal combustion engine. In such an engine, the cycle is divided into 4 cycles (4 piston strokes):
  1. The piston goes down from the top dead center, freeing the combustion chamber (cylinder) and sucking the mixture from the open intake valve.
  2. The piston moves to top dead center, squeezing the mixture. When the piston approaches it, a spark is supplied to the combustion chamber.
  3. Free piston stroke. After supplying the spark, the mixture detonates and squeezes the piston out of the combustion chamber.
  4. When the piston makes its fourth stroke, the exhaust valve opens, through which the piston squeezes the exhaust gases from the combustion chamber.


One of the easiest engine types. It is indicated by the letter "R" (R3, R4, R5, and so on). In such a motor, the cylinders are arranged in a row. There can be from two to six. The most common in-line engine is a 4-cylinder. But in history there are cars with in-line 8-cylinder engines. They stopped installing because of the long length. Inline "fours" are installed on almost all cars, the volume of which is in the range from 1 to 2.4 liters. The Fives began to be installed back in 1974 on the Mercedes-Benz W123. Later they began appearing on Audi, and in the late 80s - on cars Volvo and Fiat. Regarding the inline six, the most striking carrier of this engine is the Volvo S80, with a volume of 3.2 liters.


Next in popularity after an in-line motor. In such engines, the cylinders are located opposite each other at an angle from 10 ° to 120 ° (most often 45 °, 60 ° and 90 °) in the form of the Latin letter “V”, with an equal number of “boilers” on both sides. In such motors, pistons rotate one common crankshaft. On the nameplate, the letter “V” indicates the type of engine, and the numbers following it indicate the number of cylinders. Such motors are V6, V8, V10, V12. (not to be confused with 16V or 20V, in the case when the letter "V" is located after the numbers, it indicates the number of valves "Valve"). Almost always, these are cars with an engine capacity of more than 3 liters. But there are fewer, for example, 2.8 v6 or 2.6 v6.


Volkswagen’s famous VR6 engine is a “V-shaped in-line” motor (the VR designation indicates this). Such engines use a very small block camber, only 15 °. The angle is so small that such a motor is also called "offset-row." The most famous cars with this engine are the Golf VR6 and Passat VR6.


This motor was also developed by Volkswagen. The essence of the engine is to merge two VR-shaped motors into one at an angle of 72 °. The W12 motor was presented at the W12 Roadster concept car. It consisted of two VR6 engines. Volkswagen later presented the top-end version of the Passat B5 with a W8 engine. It was assembled from the same two VR6 engines, only with "cut off" two cylinders from each. The most famous W-shaped motor is mounted on a Bugatti Veyron. Its volume reaches 16.4 liters, and it is made of two VR8 engines.


An internal combustion engine in which the angle between the cylinders is 180 °. It differs from the V-shaped with a 180 ° camber in that the pistons opposite are reaching the top dead center at the same time, and not alternately. Boxer engine is very actively installed in cars of the Subaru brand.