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

Blipping the throttle means quickly spin the throttle and let go. During this sequence, only a small amount of air and fuel is given to the engine to rev it up just a little bit. As soon as the throttle is released, the engine is no longer revving. During this time, the clutch is released so that the engine is connected to the wheels. But since the engine is not getting fuel and air, there is no power. Without fuel and air, The piston compression and friction inside the cylinders and engine components create resistance. This resistance is what cause the bike to slow down. It’s called engine braking.

The blipping the throttle in this case is called rev matching. Where you match the engine RPM with the RPM of the clutch. They do this to make shifting smoother.

On the other hand, if they rev the engine without releasing the throttle, that’s just opening the throttle, the RPM is maintained, power is maintained. If the clutch is released with the throttle open, the rear wheel will suddenly get power. The bike will either accelerate, or lose traction.