Rev hang is a common problem with modern manual transmissions where the engine RPM does not drop immediately once you press the clutch in, even if you’re completely removed your foot from the throttle. This delay in engine RPM dropping causes the car to jerk & rough shifting in manual transmission vehicles.
source/image: Engineering Explained
What causes rev hang? Rev hang often gets blamed on heavy flywheels, but that’s not actually what causes it. It’s a result of modern cars switching to electronic throttle bodies. What’s the difference between mechanical and electronic throttle bodies?Engineering Explained
Overall, electronic throttle bodies are a good thing! They provide better tuning of cruise control, they allow for smoother shifts with automatic transmissions, they can improve how quickly catalytic converters heat up by controlling the balance of air/fuel ratios and throttle position, they can improve throttle control during cylinder deactivation, they can remove driving jerk in manual transmission vehicles.
They can provide safety features like improvements for stability control, traction control, and reducing throttle input if the brake pedal is pressed, and the list goes on! However, they can also be used to improve vehicle emissions, and this often comes with the negative side effect of rev hang. Check out the video to learn all about it!via/read more: Engineering Explained