While downshifting a motorcycle, why does the bike automatically slow down even though you need to blip the throttle and increase the rev before shifting?

Question

Seems counterintuitive

In: Engineering

Answer 1

When no throttle is applied the engine is just an air compressor which needs energy to pump. When you downshift the engine spins faster compressing more air which uses more kinetic energy and slows you down more.

Works the same for cars and especially semi-trucks. Truckers especially use this to their advantage to save on brake wear and fade going down steep mountain roads.