If you can produce the same horsepower with engines of different sizes, why are larger engines built at all?
In: Engineering
They are often under less mechanical stress and less complex than a smaller engine producing the same power. They are also often cheaper to maintain and manufacture.
So they are less sensitive to poor maintenance, poor fuel, etc.
So actually, I take the other position. If you can get the same efficiency and power out of a larger engine, why go with the smaller displacement engine?
(Hint: taxes, the majority of markets tax on engine displacement. The US does not)
Larger ones could also be lighter, I know it sounds ridiculous but think about it. They use the same materials to work on it, but one is more condensed, so the smaller one would have more mass and thus more weight
To get the same HP from a smaller engine you typically require higher compression (e.g., using a turbo) which adds complexity and cost. That and failures can be more catastrophic too.
Different sound and feel. Easier to fix and work on. Less expensive to manufacture. (Labor cost)
Horsepower is the amount of work that an engine can do in a period of time. The work can be done in multiple ways. You can push very hard, but more slowly (high torque, low rpm, like a tractor trailer engine) or you can push less hard, but much faster (race car engine, low torque, high rpm). The power from both engines could theoretically be used to drive either a race car or a tractor trailer, with the proper gearing, but that’s not all there is to the equation.
Gearboxes have practical limits, too. While not impossible, it would be practically very difficult to gear a race car engine down to toe the huge loads that a tractor trailer tows, even though it makes plenty of power. On the flip side, it would be difficult to gear a tractor trailer engine up to drive the wheels of a race car at high speeds.
Another thing is longevity at the given task. A tractor trailer engine is extremely heavy and durable, meaning that it can drive a million miles with proper maintenance. A race car engine on the other hand is very light, and runs tight on the ragged edge of failure, meaning that it will not last nearly as long as the big diesel engine in the tractor trailer will.
In short, both are made to fulfill a specific need, and neither can properly fulfill the role of the other. All engines are like this, as are most things in the realm of engineering. Finding the best way to accomplish a specific task is the primary job of an engineer.
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