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 horsepower of an engine is a function of its physical parameters – displacement, stroke length etc, plus operational parameters like friction, intake resistance etc. It doesn’t change based on which gear is selected.

Torque, on the other hand, is horsepower divided by RPM (times some coefficient). So if you keep the engine at the same horsepower but choose the gear that ends up with wheels rotating twice as slow, the torque will be doubled.