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Air-cooled engine: principle of operation, advantages and disadvantages
Air-cooled engine: principle of operation, advantages and disadvantages

Most motorists are only familiar with traditional types of engines with liquid SOD. But there are also motors that use air cooling of the engine, and this is not only ZAZ 968. Let's take a closer look at the device, the principle of operation of the air cooling system, as well as the disadvantages and advantages of such a solution. This information will be useful for every car enthusiast.


During the operation of the internal combustion engine, the temperature in the combustion chamber can reach 2000 degrees. If there is no reliable cooling system, oil and fuel consumption will increase. Overheating will cause rapid wear and damage to the engine.

why does the fan turn on

If the engine does not warm up enough, it will also have a negative effect on it. If hypothermia is observed, this threatens with a decrease in power, intense wear, and increased fuel consumption.

MoreIn addition, in most modern cars, in addition to the main tasks, this system also performs secondary functions. The first step is to ensure the operation of the heater. Also, the system is designed to cool not only the engine itself, but also the oil and fluid in the automatic transmission. Sometimes it also affects the throttle assembly along with the intake manifold.

A modern system (whether liquid or air-cooled) dissipates up to 35 percent of the heat produced by combustion of the fuel-air mixture.

Design and principle of operation

In an air system, airflow is the most important thing. With the help of air, heat is removed from the combustion chambers, cylinder head, oil coolers. The system consists of a fan, cooling fins in the cylinders and on the cylinder head. Also in the device there is a removable casing, deflectors and a solution for monitoring the operation of the system. The engine cooling fan is equipped with a mesh to protect the blades from foreign objects.

Additional ribs allow you to increase the surface area that is in contact with the air. Due to this, the air cooling of the engine effectively copes with its task.

The air flow during engine operation is forcibly supplied to the motor using fan blades - they are mainly made of aluminum. No need to explain, probably, why the cooling fan turns on on a cold engine. The air flow passes between the fins, and then is evenly divided by deflectors and passes through all hot partsengine. Thus, the motor does not get excessively hot.

Why does the cooling fan turn on when cold?

The fan delivers 30 cubic meters of air per minute to the cooling system. This is enough to ensure the normal operation of the motor with low power and small volume.

How does a fan work?

This node is the main air-cooled engine. The main part is the fan rotor. Engineers carefully considered the shape and design of the elements to optimize airflow.

The fan is a directional diffuser and a rotor equipped with eight blades arranged radially. The diffuser has its own blades - they have a variable section. Their main task is to create a directed air flow. They are made immovable and evenly distributed around the circumference.

The blades on the guide vanes are designed to change the direction of the air flow - the air flow moves in the direction opposite to the rotation of the rotor. This increases air pressure and improves engine cooling.

The fan on early designs was driven from the crankshaft pulley using a drive belt. The guide device is motionless and fixed on the engine block. In more modern four-stroke air-cooled engines, the fan is driven by an electric motor. But there are few such models.

Natural air cooling system

This is considered the easiest solution. On the outside of the blockThe engine is equipped with special ribs through which the maximum amount of heat is given off. This system can be found on motorcycles, various mopeds and scooters, piston engines for various purposes.


The main advantage among all the other advantages of an air-cooled engine is the simplicity of the design. The system lacks a pump, radiator, thermostat, pipes and clamps, antifreeze inlet and outlet pipes.

The second important advantage is high maintainability. For example, tractor power units have individual cylinders. If a breakdown occurs, then if necessary, you can replace the cylinder or eliminate the malfunction. In liquid-cooled engines, in the event of damage to any of the cylinders, you will have to change the block completely or press out the liners.

Don't look far for an example. Let's take the Tatra T815 engine. This is an air cooled motor. The block heads are made separate here. In case of need for repair, it is not necessary to remove the cylinder head completely. Even very serious repair work can be done without dismantling the engine block.

Engines equipped with air cooling are more resourceful. If the pipes are damaged in a motor with a liquid system or the clamps are loosened, then the unit cannot be operated, as the coolant will leave. There is also the danger of hot liquid ejection from the system. Air systems are deprived of all these shortcomings.

Why does the fan turn on when the engine is cold?

Even serious damage to the cooledsurfaces on the engine block or cylinder head cannot interfere with the further use of the motor. This is a very big plus. In addition, the engine needs much less time to enter the operating mode - there is no need to warm up the liquid, which is important in winter. All this leads to significantly lower maintenance and operation costs for such power units.


Not without flaws. Before you buy a car equipped with such a cooling system, you should know the main disadvantages of these solutions.

So, the operation of the engine is accompanied by excessively loud noise. This noise is created by a running fan. Another disadvantage is the size, since the motor is equipped with blowers. Even with the current pace of technology development, air flows are unevenly directed, which means that there is a risk of local overheating. Engines of this type are very sensitive to the quality of gasoline, oil, high requirements are placed on the condition of the main parts in the engine.

But cars with such a system have firmly taken their place in the automotive industry. Trucks are equipped with these power units, there are several passenger models. Air-cooled agricultural and military equipment, some diesel engines.

why is the cooling fan on a cold engine

Popular myths

The first known air-cooled car was the Zaporozhets. He completely undermined the confidence of the domestic driver in such a system. Often car owners complained about severe overheating,insufficient power and frequent failures. At the same time, the German "Beetle" with approximately the same system was very popular, the demand for it was very good.

Let's, based on the characteristics of the German automotive industry, take a closer look and debunk the popular myths that haunt engines of this design.

DVO loses to a liquid system due to overheating

This is not the ultimate truth. In fact, temperature performance, on the contrary, should be considered an advantage. Naturally, due to the reduced thermal conductivity, the air simply will not be able to remove heat as quickly as in systems with antifreeze.

why is the fan on a cold engine

But the difference between the temperature on the cylinders and the temperature of the external environment is much greater than between the liquid and the walls of the block and the cylinder head. The weather is less able to influence the temperature regime of cooling. Fluid system engines have an increased risk of overheating in summer. This is especially true on a hot sultry day. Also, owners may face the problem of why the cooling fan turns on on a cold engine. There is no such thing in "air vents".


Above, among the shortcomings, we highlighted the point about the dimensions. If we compare the sizes of motors with different types of cooling and other identical characteristics, then the advantage will still be with the "air vent".

Even though the fan and deflector are quite bulky devices, the parameters of the “air vent” are smaller than in the version withliquid cooled.

In addition, to accommodate a traditional water system, more space is needed under the hood to accommodate additional equipment. A rather large radiator with a fan is installed on the body. Hoses and pipes take up a lot of space.

Vozdushnik lose in reliability

Statistics show that one in five cases of engine failure is due to liquid cooling. The reason here is in the following details - thermostat, radiator, pump. Even the most modern air-cooled Tatra '89 engine is more reliable than the engine of the new Polo Sedan or Solaris.

As for the "air vents", the probability of breakage is much lower, since the design is much simpler - only a fan and a deflector.

Vozdushnikov loud

But this is the truth. But even the huge Tatra dump truck does not roar, the engine is just noisier. The design features do not provide for any effective sound-absorbing systems. Liquid engines have such systems. In addition, the noise is amplified by the passage of air flows through the fins of the cylinders and heads.

why does the engine cooling fan turn on

Typical malfunctions

For all the reliability of air systems, breakdowns happen here too. One of the most common faults is electronics. The system has a temperature sensor. For those who do not know where the engine temperature sensor is located: it is located in the oil pan. As a result of overestimated readings of this sensor, the system may givefailure.

If the malfunction lamp on the instrument panel lights up, then most often the reason is a broken belt. The thermostat is the least diagnosed problem.

Features of oil selection

There is an opinion that a special oil for air-cooled engines should be used. And it is. The fact is that the temperature of the load on the parts of the piston group in air-cooled engines is much higher than in units with water.

These speci alty oils are most often based on coarse polyalphaolefin oils based on mineral or synthetic nature. A set of additives has been applied to this complex, providing reliable engine protection, resisting the occurrence of rings, and improving energy saving. All oils already contain additives that effectively protect the unit from jamming due to the stable base formula.

About repair and maintenance

To operate these engines, the owner must understand a little how the system works and know where the engine temperature sensor is located. Otherwise, this is a reliable cooling system, which has no analogues in terms of the simplicity of the device. No need to change antifreeze every two years, no need to use sealant to fix leaks, and periodically change the pump. And there are quite a lot of such “not necessary” ones.

Why does the cooling fan turn on when the engine is cold?


So we figured out what an air-cooled engine is. As you can see, these are very reliable units. However, as it showsstatistics, serial cars with such internal combustion engines are very few. In most automakers, classic liquid cooling of the engine is practiced. Airborne can only be found on some trucks and scooters.

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