Difference between displacement and car horsepower

The power of a car is measured on the basis of various factors and units of measurement, in particular, reference is always made to the engine capacity and horsepower , but they must not be exchanged. Let’s see what the differences are.

What are displacement and horses for

When it comes to displacement and engine horsepower, many are confused as they think they are interchangeable. In reality they are two complementary aspects of the engine that serve to indicate the actual power of the vehicle. In general, high numbers of displacement and horsepower indicate greater engine power and therefore better vehicle performance. Obviously, there are other considerations to make, for example the weight of the car. To understand how these two technical characteristics of the engine relate, let’s see specifically how each of it works and how it is measured.

Displacement automobile

Engine displacement, also called cubic capacity, is measured in cubic centimeters (cc) and indicates the pumping capacity of the engine as a whole. The cubic volume expressed in cubic centimeters therefore serves to indicate the overall volume of fuel that the car is capable of pumping when the engine is running. A higher volume, i.e. a larger displacement, allows the engine to pump more fuel at the same time and therefore to express more power.

The displacement of the engine is indicated as a whole, that is, the sum of all the cylinders present is made and everything is expressed through a round digit number, even if the sum is different but the difference is minimal. For example, the description could indicate that a car has a displacement equal to 1000 but overall it is 998 cc. Generally the differences are so small that they have no real influence on the performance of the machine. If you want to know the real displacement of a vehicle at all costs , this is clearly indicated in the technical documents of the car and obviously also in the booklet.

When you find yourself looking at an advertisement or a description of a car, if you notice it, the exact number of the car’s displacement is almost never indicated. But often you will find among the technical characteristics words such as ‘1.0 petrol’. In this case 1.0 indicates the cubature of the engine , simply by rounding up to round numbers, just multiply the number by a thousand. 1.0 therefore means that the displacement is equal to 1000.

What are the horsepower

The number of horses instead serves to indicate how much power the engine can express. This curious unit of measurement derives from the past, when steam engines spread throughout Europe during the first industrial revolution in the 18th century. In order to understand how much power an engine is, it was compared to horses, specifically s trying to understand how many horses were needed to perform the same job as the machinery. Obviously today we realize that it is not a completely reliable unit of measurement because there are many variables related to horses (age, musculature, strength, etc.), so a horsepower is considered to be the ability to lift 75kg at the speed of one meter per second.

The unit of measurement of the horse is well known in the world, in fact in Italy it is indicated with the wording CV while in America and in the Anglo-Saxon countries it is used Hp, ie Horse Power. However, Hp and CV are not the same, so much so that 1 CV = approximately 0.98 Hp. Such a discrepancy could cause you many problems if you have to evaluate the power of a car that does not come from Italy, for example for a purchase or rental in a foreign country.

Horsepower clearly expresses how strong the engine is . The horse, given the differences between one country and another, is not even recognized in the International System of Measurements. So how can you know the real power of a vehicle without having to consult dozens of tables? What really matters are the kilowatts of the engine(kW), a unit of measurement recognized in the International System which expresses the real power of the engine. The Watt, in the SI, is equivalent to 1 joule per second. With the same power, the kilowatt is a higher unit of measurement than the endorsements, so in simple terms 1 kW = about 1.36 HP, so a car with 100 kW will have about 136 horsepower. Many people tend to confuse horses with watts as equivalent, but remember that watts are necessarily less than horses. To date, horses are often indicated instead of watts for the simple fact that they are better known than the precise unit of measurement, therefore they are used by custom and it is easy to remember them as car power.

How displacement and horsepower are related

In short, the engine owes its power to two main factors: the displacement, which indicates how much fuel it is capable of pumping at the same time, and the watts, which indicate how much energy the engine is capable of expressing. Wanting to evaluate two different cars, one with a 120 horsepower 1.5 engine and a 1.9 with 100 horsepower, what is the most efficient engine? You may think that the first with more horsepower but with a smaller displacement makes the car go faster, then you realize that the 1.9 car goes faster. The substantial difference will lie in the fact that the 1.5 will consume less, guaranteeing excellent performance, while the 1.9 will burn more fuel to go faster than the first, even if it has less horsepower.

Ultimately the two numbers by themselves make it clear how powerful an engine is but the actual performance of the vehicle depends on several other factors. First of all, from the type of fuel it feeds (diesel engines, with the same power, burn diesel fuel in a different way than petrol-powered cars), the general state of wear and above all the type of vehicle. The trucks have very powerful engines, some with a displacement of 6000 but in fact they are slower than a small car. However, such a vehicle needs a lot of power to move. When evaluating a car, therefore, don’t rely only on displacement and horsepower, but check all the other contextual factors.


by Abdullah Sam
I’m a teacher, researcher and writer. I write about study subjects to improve the learning of college and university students. I write top Quality study notes Mostly, Tech, Games, Education, And Solutions/Tips and Tricks. I am a person who helps students to acquire knowledge, competence or virtue.

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