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

No. If you gear down you get more driving force at the rear wheel at the expense of top speed at engine’s rpm limit. If you gear up you get a higher top speed at the expense of driving force. Which is why you use a transmission in the first place.

Get on a bicycle with multiple gears. Put it in the highest gear. Try and accelerate rapidly. It will be very difficult, because the driving force at the rear wheel is reduced due to the gear ratio. Now put it in a low gear and you’ll find acceleration is much easier. Don’t shift up, and see how fast you can go in that low gear. You’ll spin out at a pretty low speed. Shift up to increase your top speed.