All about engine size

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One of the main characteristics of not only the internal combustion engine itself, but also the vehicle as a whole is the working volume of the power unit. It largely depends on how much power the engine is able to develop, to what maximum speed it is possible to accelerate the car. In many countries, it is the working volume of the engine that is the parameter by which the amounts of various taxes and fees paid by the owner of the vehicle are determined. The importance of this characteristic is also emphasized by the fact that its value in one form or another is often indicated in the name of the model.

Nevertheless, not all motorists clearly understand what is meant by engine displacement, what depends on it, and what engine displacement is best for certain operating conditions.

What is called engine displacement

The general principle of operation of a piston internal combustion engine can be described as follows. A mixture of fuel and air is supplied to the cylinders in a certain proportion. There it is compressed by pistons. In gasoline engines, the mixture is ignited due to an electric spark from, in diesel engines, it spontaneously ignites due to a sharp heating caused by strong compression. Combustion of the mixture causes an intense increase in pressure and expulsion of the piston. He makes the connecting rod move, which in turn sets in motion. Further, through the transmission, the rotation of the crankshaft is transmitted to the wheels.

In its reciprocating motion, the piston is limited by top and bottom dead center. The distance between TDC and BDC is called the stroke of the piston. If we multiply the cross-sectional area of ​​the cylinder by the piston stroke, we get the working volume of the cylinder.

In most cases, the power unit has more than one cylinder, and then its working volume is determined as the sum of the volumes of all cylinders.

It is usually indicated in liters, which is why the expression “displacement” is often used. The value of the volume is usually rounded up to the nearest tenth of a liter. Sometimes cubic centimeters are used as a unit of measurement, for example, when it comes to motorcycles.

Engine size and classification of light vehicles

Any automaker in its model range has cars of various classes, sizes, configurations, designed for different conditions of use, needs and financial capabilities of buyers.

Currently, there is no single classification of vehicles based on engine size in the world. In the Soviet Union, there was a system that divided car engines into 5 classes:

• extra small with a volume of up to 1,1 l;
• small - from 1,1 to 1,8 liters;
• medium - from 1,8 to 3,5 liters;
• large - from 3,5 to 5,0 liters and above;
• the highest - in this class, the engine size was not regulated.

Such a classification was relevant when atmospheric engines powered by gasoline dominated. Now this system can be considered obsolete, since it does not take into account the features of diesel engines, turbocharged units and other engines that use new technologies.

Sometimes a simplified classification is used, according to which motors are divided into three categories. From 1,5 liters to 2,5 liters - medium displacement engines. Anything less than one and a half liters refers to small cars and minicars, and engines over two and a half liters are considered large. It is clear that this system is very conditional.

The European classification of passenger cars divides them into target market segments and does not strictly regulate any technical parameters. The model belongs to one or another class based on price, dimensions, configuration and a number of other factors. But the classes themselves do not have a clear framework, which means that the division can also be considered conditional. The classification looks like this:

• A - extra small / micro / city cars (Mini cars / City cars);
• B - small / compact cars (Small cars / Supermini);
• C - lower middle / golf class (Medium cars / Compact cars / Small family cars);
• D - medium / family cars (Larger cars);
• E - upper middle / business class (Executive cars);
• F - executive cars (Luxury cars);
• J - SUVs;
• M - minivans;
• S - sports coupe / supercars / convertibles / roadsters / gran tourism.

If the manufacturer considers that the model is at the junction of segments, then the “+” symbol can be added to the class letter.

Other countries have their own classification systems, some of them take into account engine size, some do not.

Displacement and engine power

The power of the power unit is largely determined by its working volume. However, this dependence is not always proportional. The fact is that power also depends on the average effective pressure in the combustion chamber, on energy losses, valve diameters and some other design features. In particular, it is inversely proportional to the length of the stroke of the pistons, which in turn is determined by the ratio of the dimensions of the connecting rod and the connecting rod journals of the crankshaft.

There are opportunities to increase power without increasing the working volume of the cylinders and without additional fuel consumption. The most common methods are the installation of a turbocharging system or variable valve timing. But such systems significantly increase the price of the car, and in the event of a breakdown, repairs will also be very expensive.

The reverse action is also possible - automatic reduction of engine power when it is not fully loaded. Engines in which electronics can turn off individual cylinders are already used on some production cars produced overseas. Fuel economy thus reaches 20%.

In addition, prototypes of internal combustion engines have been created, the power of which is regulated by changing the stroke length of the pistons.

What else affects the working volume

The acceleration dynamics of the car and the maximum speed that it is able to develop depend on the displacement of the internal combustion engine. But here, too, there is a certain dependence on the parameters of the crank mechanism.

And of course, the displacement of the unit affects the cost of the car, moreover, very significantly. And it's not just about increasing the cost of producing the engine itself. To work with a more powerful engine, a more serious gearbox is also needed. A more dynamic vehicle requires more efficient and powerful brakes. More complex, more powerful and more expensive will be the injection system, steering, transmission and suspension. will obviously also be more expensive.

Fuel consumption in the general case is also determined by the size of the cylinders: the larger they are, the more voracious the car will be. However, not everything is clear-cut here either. With a quiet movement around the city, small cars consume about 6 ... 7 liters of gasoline per 100 km. For cars with a medium-sized engine, the consumption is 9 ... 14 liters. Large engines "eat" 15 ... 25 liters.

However, in a more tense traffic situation in a small car, you often have to maintain high engine speeds, gas, switch to lower gears. And if the car is loaded, and even the air conditioner is on, then fuel consumption will increase significantly. At the same time, acceleration dynamics will also noticeably worsen.

But as for the movement on country roads, at a speed of 90 ... 130 km / h, the difference in fuel consumption for cars with different engine displacements is not so great.

Pros and cons of ICE with large and small volume

When choosing a car to buy, many are guided by models with a large engine capacity. For some it is a matter of prestige, for others it is a subconscious choice. But do you really need such a car?

Increased displacement is closely related to higher power, and this, of course, should be attributed to the advantages. The powerful engine allows you to accelerate faster and feel more confident when overtaking, changing lanes and driving uphill, as well as in various non-standard situations. In normal urban conditions, there is no need to constantly spin such a motor to high speeds. The included air conditioner and full load of passengers will not have a significant impact on the dynamics of the vehicle.

Since large- and medium-displacement units are operated, as a rule, in a not too intense mode, their efficiency turns out to be quite high. For example, many German cars with 5-liter and even 3-liter engines can easily provide a mileage of a million kilometers or more without. But small car engines often have to work at the limit of their capabilities, which means that wear and tear, even with careful care, occurs at an accelerated pace.

In addition, in the cold season, a large volume allows the engine to warm up faster.

There are large-capacity and significant disadvantages. The main disadvantage of models with a large engine is the high price, which increases sharply even with a small increase in displacement.

But the financial aspect is not limited to just the purchase price. The larger the displacement of the engine, the more expensive maintenance and repairs will cost. Consumption will also increase. The amount of insurance premiums depends on the working volume of the unit. Depending on current legislation, the amount of transport tax can also be calculated taking into account engine displacement.

Increased fuel consumption will also increase the operating costs of a large vehicle. Therefore, aiming at a powerful "beast", first of all, carefully evaluate your financial capabilities.

The problem of choice

When choosing a car, it is better to avoid class A models with an engine capacity of about 1 liter or less. Such a car does not accelerate well, it is not very suitable for overtaking, which in some cases can even be dangerous. The loaded machine will clearly lack power. But if you are going to ride alone, do not feel cravings for recklessness, and you are running out of money, then this option is quite acceptable. Fuel consumption and operating costs will be low, but it is hardly worth counting on a long trouble-free operation of the engine.

For many motorists without increased claims, the best choice would be a class B or C car equipped with an engine with a displacement of 1,3 ... 1,6 liters. Such a motor already has good power and at the same time does not ruin the owner with excessive fuel costs. Such a car will allow you to feel confident enough both on city streets and outside the city.

If funds allow, it is worth buying a car with an engine capacity of 1,8 to 2,5 liters. Such units can usually be found in class D. Accelerating from a traffic light, overtaking on a highway or a long climb will not present any problem. A relaxed mode of operation will ensure good durability of the motor. In general, this is the best option for a family car. True, the cost of fuel and operation will be slightly higher.

Those who need decent power, but want to save on fuel, should take a closer look at models equipped with a turbocharger. The turbine is able to increase engine power by 40 ... 50% with the same engine size and fuel consumption. True, a turbocharged unit requires proper operation. Otherwise, its resource may be limited. This nuance must be taken into account when buying a used car.

For off-road use, you cannot do without a powerful unit with a volume of 3,0 ... 4,5 liters. In addition to SUVs, such motors are installed on business class and executive cars. Not everyone can afford these cars, not to mention the fact that their appetites for fuel are very high.

Well, those who have unlimited funds do not pay attention to such trifles. And they are unlikely to read this article. Therefore, it simply makes no sense to give recommendations regarding the purchase of a vehicle with a unit displacement of 5 liters or more.