[Reading Science] Mysterious Car Terms - ① Power and Fuel Efficiency

A vehicle traveling at high speed. What is the exact meaning of "horsepower," which refers to the engine's output? [Photo by YouTube screen capture]

[Asia Economy Reporter Kim Jong-hwa] "The official certified fuel efficiency is 18.9 km/L. Even compared to the 1.5 Turbo (13.9 km/L) that uses the same CVT transmission, it has a relatively generous fuel efficiency, and at the same time, thanks to the assistance of the electric motor, it delivers a system maximum output of 215 horsepower."

This is a part of an article introducing a newly released car. It explains the car's output and fuel efficiency, which are essential pieces of information for people intending to purchase a vehicle. What can you understand from this one sentence?

They emphasized the high fuel efficiency by using the somewhat exaggerated phrase "official certified fuel efficiency," and honestly, I don't know exactly what a CVT transmission is. I roughly understand that the 1.5 Turbo engine has a fuel efficiency of 13.9 km/L and that the maximum output is 215 horsepower. Is that correct? I guess most of you have a similar understanding as I do, right?

Let's start with something easy. The unit of car output is "horsepower (馬力)." Most people, like me, understand horsepower as a unit representing the power of a horse. While this is not entirely wrong, it is more accurate to understand it as the "amount of work" or "work efficiency (power)." In other words, it indicates how much work is done per unit of time.

So, "1 horsepower means the amount of work to lift a 75 kg object by 1 meter in 1 second." The units HP and PS are used interchangeably; HP (Horse Power) is used in English-speaking countries that use the yard-pound system, while PS (Pferdest?rke) is used in countries that use the metric system. Since Korea uses the metric system, it naturally uses PS.

"Pferdest?rke" is a German word combining "Pferde (horse)" and "St?rke (power)," and French-speaking countries sometimes use the abbreviation CV from "Cheval (horse)" and "vapeur (power)." Work efficiency is expressed as the amount of work done per unit time (1 second), with the unit being watts (W). 1 W means the power when 1 joule (J) of work is done in 1 second.

Converting horsepower to work efficiency, 1 PS equals approximately 0.7355 kW. Calculated in HP using the yard-pound system, 1 HP equals about 0.7457 kW. Although the horsepower is the same, there is a difference depending on whether the metric system or the yard-pound system is used. This is why the metric system, the international standard, should be used.

'1 horsepower' refers to the amount of work required to move a 75 kg object 1 meter in 1 second.
[Photo by YouTube screen capture]

The car introduced in the article has a maximum output of 215 horsepower, which converts to about 158 kW in terms of power. Comparing this figure to electricity consumption, it is equivalent to the amount of electricity needed to operate a large commercial refrigerator for about a month. In other words, the maximum work efficiency (amount) the car can produce while driving is comparable to the electricity required to run a large commercial refrigerator for a month.

Fuel efficiency is the ratio of driving distance per unit of fuel. In Korea, the Energy Management Corporation measures the fuel efficiency of cars and publishes it on their website, calling it "certified fuel efficiency." However, even this differs in notation from country to country, which can be confusing.

Korea expresses fuel efficiency as "km/L," indicating how many kilometers can be traveled with 1 liter of fuel. Asian and South American countries such as Japan, India, and Brazil also follow this method. Europe uses "L/(100 km)," which indicates how many liters of fuel are needed to travel 100 kilometers. Europe, Canada, Australia, and New Zealand use this method.

The United States, which does not follow the international standard and uses the yard-pound system, is complicated because it must convert to the metric system. The US uses "mile" for distance and "gallon" for fuel volume, so fuel efficiency is expressed as "mpg," an abbreviation for "mile per gallon." 1 mpg means that 1 gallon of fuel can travel 1 mile, which converts to approximately 0.425 km/L in the metric system.

Therefore, when comparing fuel efficiency of cars from different countries, in Korea and the US, a higher number means better fuel efficiency, while in Europe, a lower number means better fuel efficiency. For example, if a car with a Korean fuel efficiency standard of 12 km/L drives 100 km, dividing 100 by 12 shows that about 8.3 liters of fuel are needed, which is expressed as "8 L/(100 km)" in Europe, making it easy to understand.

Do you have some understanding of output and fuel efficiency now? Car terminology can be quite puzzling. When introducing engine performance, terms like torque and RPM appear, but often people just roughly think, "Well, it means the engine is good," without fully understanding.

We will look into some car engine performance terms in the [Car Terminology Mysteries - ② Torque and RPM] installment.