The Big Problem With Modern Manual Transmissions - Rev Hang

What Is Rev Hang And How Does It Ruin Manual Transmission Shifting?

1w ago

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What is rev hang? 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.

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?

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!

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Comments (14)

  • You're a very good YouTuber!

      7 days ago
  • The throttle dashpot fell off my new truck long ago.

      6 days ago
  • I was just describing a problem with my 911 Targa 4 GTS that sounds very similar. It makes it very hard to upshift smoothly especially when you have auto blip on.

      7 days ago
  • 2017 wrx had this problem and hated the car for it. 2020 sti don't.

      4 days ago
  • I think ( at least with Honda ) there is a 100 m second throttle delay after neutral is seen by the vecu or what ever they call that main module. I know with MACK/ Volvo truck vecu’s I have the parameter logic to do a similar function for pto operation

      4 days ago
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