Why does the engine speed increase when going downhill?

[CaliLee]

Because when going downhill without applying the brakes, the speed continuously increases, leading to higher engine RPM, which naturally results in louder engine noise. Therefore, if you don't use the brakes to limit the speed while going downhill, this situation is normal. Here is more information about driving downhill: 1. Precautions: Reduce your speed before descending to enter the downhill slope at a slow pace; shift into an appropriate gear before descending, generally choosing second or third gear. 2. Downhill operation: Avoid sudden steering wheel movements on downhill sections, as the high inertia and speed combined with improper steering can easily cause the vehicle to overturn; never coast in neutral on downhill sections—always engage an appropriate gear to utilize the engine's braking effect and reduce the vehicle's coasting speed.