If an engine with high horsepower can gear down to increase torque, couldn’t a high-torque engine be geared up to increase horsepower?

Question

Just wondering why, in these discussions, people always say the former and not the latter.

In: Engineering

Answer 1

The torque of the engine does not change when gearing down, it is the output that is multiplied. The engine is producing the same amount of horsepower and torque, but by using gears you can multiply that force on an object (usually a rotating shaft). This is why we talk about engine torque and torque at the wheels when discussing about the power of trucks.

Simple way to understand this, you on a bike. You are the engine, by using a bigger rear cog when climbing a hill, you the “engine” are not magically producing more power and force, you produce the same, but that force is now multiplied at the output allowing to climb easily.