What is engine displacement and what does it affect?

Engine displacement: what is this value, what does it affect

The engine is the most important component of any vehicle, and most people associate its liter with the capacity of the power unit. In general, this approach can be considered consistent with the truth.

Passenger car engine

But behind the numbers 1.1, 2.0, 3.5, we see only the parameter, which defines the class of the car: a micro-liter car, a small car, a golf-class or a large-capacity car. What is engine displacement on a physical level, not everyone understands.

Cylinder displacement

The widespread definition of the engine displacement is as follows: it refers to the total value of the cylinder volume of the power unit, and the piston volume should be understood as the product of its stroke length by the area of the upper projection. The stroke of the piston, in turn, is the distance between the upper and lower dead points. Thus, the working volume of the cylinder is the volume of the combustion chamber, in which the energy processes occur – the ignition of the combustible mixture and its combustion.

In the intake stroke, the cylinder is filled with fuel-air mixture, which ends when the piston is in the lower MT. When the piston moves in the opposite direction, the combustible mixture is compressed and ignited.

The compression ratio is determined by dividing the total cylinder volume (when the piston is in the MMT) by the combustion chamber volume (BMT). The higher the compression ratio, the more force the mixture exerts on the piston during combustion and expansion, i.e. the power of the engine directly depends on this ratio.

Thus, it is sufficient to increase the compression ratio in order to increase engine power. But in fact, everything rests in a certain compression limit, above which the mixture combusts without a spark or burns so quickly that the engine begins to detonate and work unstably.

The symptoms of detonation are tapping noises coming from the engine, the presence of thick black exhaust, and a drop in power output. Carmakers are working hard to increase compression to get rid of detonations, but they are finding it increasingly difficult to do so.

The increase in power also depends on the crankshaft rotation speed, but this indicator cannot be increased indefinitely: the fuel mixture will not have time to get into the cylinder, there are problems with the exhaust gases, and the wear of parts with increasing speed also increases.

Modern engines are multi-cylinder. This means that the displacement of the engine is the arithmetic sum of the total volumes of all cylinders, and the larger it is, the higher the car class and the more powerful the power unit.

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Multi-cylinder car engine

Why do you need to check the engine displacement?

The average motorist does not need this indicator strictly speaking, but there is a category of drivers, who are trying to get every little bit out of their engine. They need to know the working volume of the combustion chamber in order to increase the compression ratio, which is achieved by such a tricky method as cylinder boring.

This method is considered almost the only available way to increase the engine power, and very economically advantageous – because with the same volume of fuel mixture useful work is performed much more. But, as we have already noted, it is necessary to observe a measure here: if the compression ratio is increased beyond the threshold, the mixture will spontaneously ignite, which will lead to unstable operation, reduced power and even the destruction of the power unit.

Cylinder Volume Calculation

Ithaca, let’s consider the methodology of how to find out the working (not full) volume of the engine. We have already called the general formula: this is the result of multiplying the volume of 1 cylinder by their number in a given ICE. And the volume of the cylinder is defined as the multiplication of R 2 *L*π.

The length and diameter of the piston is accepted to denote in millimeters, the volume of the power unit – in cubic centimeters, so the obtained result is divided by 1000.

It should be understood that the concepts of total/operating volume are not identical, since the piston has grooves, convexities and other geometric details, plus it is necessary to take into account the volume of the combustion chamber. If the influence of the geometry of the cylinder is minimal, the volume of the combustion chamber must be taken into account: the total volume is obtained by adding the working and combustion chamber volumes.

Thus, it is possible to determine the working volume of the cylinder (of course, also of the power unit) with the help of a calculator, it is enough to know the initial data. But if these figures are not at hand, you can use online calculators, many of which can also determine the power unit, as these are interdependent indicators.

Often, the volume of the motor is referred to as liters and indicated not in cubic centimeters, but in liters. Thus, 1300 cm3 is equivalent to 1.3 liters, that is, the resulting value should be divided by a thousand.

Calculation calculator of car engine volume

Calculating the volume of the motor online calculator

Finding a site that offers such a calculator is not a problem. To calculate the working volume of the engine, you just have to enter three digits into the appropriate fields and click the button calculate (sometimes the result is calculated and automatically, once you have entered the last digit). The initial data can be taken from the passport data of the vehicle.

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Usually, the value in cubic centimeters is very rarely a whole, so when converting to liters they are rounded using generally accepted rules: 1,598 cc 3 = 1.60 liters, 2,429 cc 3 = 2.40 liters.

There are engines, which have the same working liters and number of cylinders, but their diameter is not the same – in this case the piston stroke will be unequal, and the power of each of them will be different. A motor with a small stroke is more voracious and is characterized by a lower efficiency, but higher power achieved at high revolutions. The long stroke ones have the opposite – they are more economical and have better traction at all crankshaft rpm ranges.

Although power depends on the engine capacity, this dependence is not linear and includes other indicators, which means that to determine the volume of the engine by horsepower is not possible, the exact calculation is made only on the basis of data on the piston group.

Engine displacement increase

There is a category of car owners, for whom the task of increasing the motor power becomes an end in itself. Such an event, which has several names (chip tuning, motor tuning, engine boosting), can be performed independently.

The powertrain consists of cylinders (usually a multiple of 4), which are arranged in a common housing (BC). Inside the cylinder, a piston runs up and down, and everything together is the combustion chamber, the specifications of which form the engine’s capacity.

How is it possible to increase the power of the engine if all its parameters are carefully calculated by the car manufacturer? There are several ways to achieve the desired goal, the choice of which depends on your ambitions and financial capabilities.

The simplest and cheapest variant is cylinder boring, which allows increasing capacity. But it is necessary to install new pistons with changed radius.

A more costly option is to install a crankshaft with an increased crank radius. This increases the diameter of the connecting rods, so the entire piston group has to be replaced. Increased power is achieved by increasing the stroke of the pistons, which allows increasing the engine capacity.

Note that boosting the motor at home requires the use of specialized equipment regardless of the chosen method, as well as the availability of appropriate experience. The slightest mistake is fraught with very serious consequences, so such work is usually trusted to professionals – specialists tuning atelier.

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Engine displacement – how it works and what it is, what affects it

The engine is the heart of the car, that is why while choosing a car buyers often pay attention to one important factor – its volume. However, very few people know what the engine displacement is and what it affects.

Let us start with the definition – the engine displacement is the sum of all the volumes of the car’s cylinders, where the piston volume is the product of the piston area by its stroke, and the distance from the top dead center to the bottom dead center is called the piston stroke. To put it simply, the cylinder volume is the volume of the combustion chamber, where the ignition and combustion of fuel takes place.

Engine volume is counted in cubic centimeters or liters. One liter is 1,000 cubic centimeters. Depending on the volume, cars are divided into micro-liter – up to 1.1 liters, small-liter – 1.2-1.7 liters, medium-liter – 1.8-3.5 liters and large-liter – over 3.5 liters. This division mainly applies to cars with gasoline engines.

How does a car engine work?

To begin with, to make it clearer what we are going to talk about, let’s consider how the working process occurs in a car engine, and at the expense of what the car can move.

Imagine a closed chamber, where one wall is a moving piston. A mixture of fuel (gasoline) and air is placed there through a special spigot, and then ignited by a special device – a spark plug. The mixture flares up and instantly burns, in fact – explodes. The red-hot gas resulting from combustion pushes the piston.

On the reverse side, the piston is attached to the crankshaft, through which the pushing force is transmitted to the wheel axle that propels the car. The more fuel burned, the stronger the push will be.

Accordingly, a larger combustion chamber will provide more engine power than a small one. This is, of course, a very simplified explanation; in practice, power is affected by many factors.

What is engine displacement?

The chamber where the fuel/air mixture burns is, in other words, called an engine cylinder. In modern car engines, these cylinders (cylindrical shaped chambers) are usually several – four, six, eight or even twelve.

The volume of an engine is defined as the total volume of all cylinders, or the volume of one cylinder multiplied by the number of cylinders. The volume of one cylinder is determined at the moment when the piston is lowered to the stop, to the lowest point. The volume of an engine can be expressed in cubic centimeters or in liters (vehicle liters).

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How cars are divided into classes based on engine displacement

In the model range of each manufacturer there are products that differ by class, weight, overall dimensions and other characteristics. As for passenger cars, during the total dominance of atmospheric gasoline engines, there was a conditional division into: subcompact and compact micro and small cars with a working volume of up to 1.2 liters; small class cars with engines from 1.2 to 1.8 liters; middle class with a volume from 1.8 to 3.5 liters. powerful civil and sports versions of cars with engines from 3.5 liters and more; top class versions, which may have different volumes of ICE. Let’s take a look at what the engine volume affects.

Installation of a particular motor on a particular model directly depends on what characteristics the car should demonstrate (acceleration dynamics, torque, maximum speed, etc.). The volume of the engine makes the power indicator dependent on the fact that the more fuel is burned in the combustion chamber per cycle, the more energy is released and transferred to the piston. In other words, the larger the combustion chamber, the more fuel-air mixture can be fed and stored there. Acceleration dynamics and “top speed” also depend on engine power. The more powerful the engine, the higher speed the car will be able to reach.

You should also take into account that an increase in the volume of the chambers automatically means more fuel consumption. It should be added that the volume of the engine strongly depends on the price of the car. For example, a powerful V12 engine with a displacement of 5.5 liters requires much higher costs than a three-cylinder engine with a displacement of 0.8 liters. At the same time, it should be taken into account that installing a powerful power unit under the hood will require serious revision of the transmission, cooling system, intake, exhaust, braking system, etc. Based on the above, small budget urban small cars are often equipped with an internal combustion engine with the smallest volume, as such engines are simple to produce, provide acceptable dynamics and have low fuel consumption. At the same time, the price of such production cars remains acceptable.

What does the engine displacement affect?

  • Firstly, the gasoline consumption. The bigger is the cylinder volume, the more fuel is needed to ignite it with the highest efficiency, and thus the consumption increases. However, this disadvantage is no less tangible plus. The larger the volume of the engine, the more power the engine has, since more gasoline releases more energy
  • Secondly, as already noted, the greater the volume, the more power, that is, a car with a larger volume engine will accelerate faster, will be able to carry more heavy loads and more passengers
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Often, larger volume engines are much more economical: you do not have to put too much pressure on the gas pedal to accelerate the car. Fuel consumption does not increase, whereas small engines burn a lot more fuel under load.

The bigger the volume, the bigger the engine itself, the bigger the car. Let’s say that larger volumes are used in cars of higher class, that is why the engine and all other systems are more expensive to maintain. The price for such a car is knowingly higher.

In order to understand which car is more suitable for you, you should learn that the micro- and small-capacity cars are best suited for driving in large cities with traffic jams on the roads. Their consumption will be in the urban stream is minimal compared with other cars, but in turn, these cars are not suitable for long journeys, since at speeds over 100 km / h they clearly lack the power. A lot of cargo they can not carry as well.

Cars with a volume of 1.8 to 3 liters are perfect for urban traffic, and for long journeys, their power is enough for acceleration and driving at high speed, for cargo transportation, and the gasoline consumption of such cars is not so great.

Cars equipped with engines from 3 liters are either off-roaders, or vans and minivans, designed to carry more passengers or cargo.

Increasing engine displacement

Physically increasing the volume of the combustion chamber is one way to boost the engine in order to increase power. To begin with, it is not possible to greatly increase the volume, since the engine cylinder block is usually designed to bore the cylinders themselves strictly to certain limits. These limits involve 3 major overhauls, during which worn cylinders are bored to return them to their correct shape before installing repaired pistons, piston rings and other oversized elements. Pistons and other engine parts that are commercially available are also found exclusively in three repair sizes. For this reason, when deep tuning a car engine, it is better to change the engine immediately, that is, to install another engine with initially larger displacement, which can then be further bored into the second or last repair size.

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