What does “horsepower” mean for an Engine?

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I’m confused about the meaning of this word. Is it how much a horse can pull translated into how much the engine can pull? Also, what is the actual “metric”? Why do we still use this? It seems archaic.

Also, what type of horse was originally used to get the measurement?

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Anonymous 0 Comments

Once upon a time they used horses to pull stuff.

When locomotives were invented, they invented a unit to say how powerful the engine was. “the power necessary to lift a total mass of 33,000 pounds one foot in one minute” was chosen as a unit and named horsepower. It was more or less what an horse would do in average without getting tired. Basically, you could replace 10 horses with 10 horsepower engine. It was quite a wild approximation but, hey, at least we have a unit.

It has nothing to do with the real horse if pushed to the limit, a real horse in a sprint is actually delivering something between 4 and 8hp. Im digressing. So horsepower was the name of a unit used to promote and compare steam engines.

Anyway, power is defined as “things done per second”, like, how many kilograms can you lift one meter in a second. There are many units to measure it, and the horsepower (again, not an actual horse of power) is the hystorical favorite. Nowadays we prefer the Kilowatt as a unit, it’s better for math and it can be used in multiple fields.

Anyway, your car engine has a maximum power, this power defines the maximum things per second your car can do.

Example: your car is stationary and you floor the gas to accelerate. A 100 Hp engine will make your car go faster by a certain amount per second. If you double the horsepower you will add twice as much speed per second, aka, you double your acceleration.

If you go uphill, more power means you will be able to go uphill faster, or carry more load uphill for the same speed.

So, when you buy a car, the horsepower is a useful unit to determine what your car will be able to do. If you want to save money, you can get a small engine with less power, it will cost less to buy and will consume less fuel. However, if you want a sporty car you want to have more power.

Once you have a car, you are stuck with whatever power it has. But before buying, its an important stat to look.

Broadly:

50-100hp economic to standard car. Good but if you use this economic car to race uphill your engine will really suffer and overheat.

100-200 standard to quite quick car, will have no trouble quickly overtaking any vehicle, even uphill. Also will suffer less in hot climate and in the mountain.

200-1000 hp: something between ok you are rich and you have spare money for gas, and you dvrooom vroom and you can go from stationary to breaking the speed limit, crash and go to jail in a matter of seconds. Not practically useful but feels powerful.

2000-20000 kw you are actually driving a locomotive or a set of locomotives.

100000 hp is roughly a Boeing 777

212000 hp… sry that’s not a car that’s USS IOWA aka “it’s nice to have guns but it’s even nicer if no one can run away from you”

Rough conversion: 1 hp = 3/4 kw. 100hp=75 kw and so on.

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