Let’s talk about rev hang

[MrBD1348]

Anybody with 18+ mt-82 GT notice a significant delay/hanging revs during gear change? I feel as though my changes could be significantly faster if I wasn’t hanging around waiting for the rpm to drop and release the clutch.

ive noticed that if I don’t wait for that rpm to drop then the shift will be abrupt and I’m sure that cannot be good for clutch wear. This is my first manual car so I’m still learning. But I’m comfortable enough with the car now that I am trying to shift quicker. At first I was blaming the throw distance and shifter. But now it seems that I’m waiting around even with stock shifter.

I’ve asked my tuner about this and was advised that the shift logic can either be on or off. I asked if there was a possibility to trim the decay time between shifts. So I’m clueless at this point. Can it be fixed with a tune? Or any other mods?

I’m all ears for learning. Thank ya

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[Rael]

I'm not sure this would be the cause of your issue, but do you use the automatic rev-matching? I can't use it for street driving at all.

 

[KeyLime]

I have a '21 and have not seen bad rev hang problems. I was worried about it when I ordered the manual but it hasn't been an issue. For what it's worth I've been driving manuals since the 3 on tree days so I think my expectations are somewhat normal.

 

[Bulldog9]

I'm back on the throttle to fast to notice.

If you are new to manual shifting work on your technique and movements/timing and stick to lower rpms until your technique is solid and you've learned your car. You may not be fully disengaging the clutch (i.e. not pressing the pedal far enough.

Then start working on the speed of your shifts. Once you have that nailed, then start shifting at higher revs. These cars build speed too quickly to fool around.

 

[CrackedHorn]

I'm back on the throttle to fast to notice.

If you are new to manual shifting work on your technique and movements/timing and stick to lower rpms until your technique is solid and you've learned your car. You may not be fully disengaging the clutch (i.e. not pressing the pedal far enough.

Then start working on the speed of your shifts. Once you have that nailed, then start shifting at higher revs. These cars build speed too quickly to fool around.

Can't speak for OP but a lot of folks have this issue and complain about excess rev hang. My car does it, too and this isn't some issue unique to inexperienced drivers. Being "quick on the throttle" only exacerbates the rev hang issue as the RPM is mismatched while the revs hang.

 

[Bulldog9]

Can't speak for OP but a lot of folks have this issue and complain about excess rev hang. My car does it, too and this isn't some issue unique to inexperienced drivers. Being "quick on the throttle" only exacerbates the rev hang issue as the RPM is mismatched while the revs hang.

What RPM are we talking, and what is the issue? Causing lockout?

 

[CrackedHorn]

What RPM are we talking, and what is the issue? Causing lockout?

The RPM varies depending on when you shift .

When you disengage the clutch, the computer tells the engine RPM to "hang" in place for a bit rather than just naturally allowing revs to drop.

So when you go to upshift, you have to shift slower than normal if you want it to be smooth. Quickly getting back onto the throttle makes the car herky jerky. This effect in my car is also much more pronounced when the trans/engine is cold. And the whole issue itself can be intermittent. This transmission is a fickle partner.

 

[NGOT8R]

I had Rev hang on my 2019 Bullitt. Revs would hang between 1500-1800 whenever I depressed the clutch to come to a stop. My tuner said it was caused by turbulence from the PMAS CAI kit. It eventually worked itself out after several drives though.

 

[Vlad Soare]

Most of the rev hang is caused by the auto rev match. Disabling the ARM will cure that.
There's still a bit of rev hang without the ARM, but that's on par with most other contemporary fuel-injected engines and is quite tolerable. A custom tune can get rid of that, too.

I can't use it for street driving at all.

You can, but you must change your technique and use the pedals like someone who's driving for the first time in their life would. It took me a bit of time to get used to it, but in the end I was able to drive extremely smoothly in all situations. The problem is, as soon as I was in a different car I felt like I had forgotten how to drive properly. I was jerking it like a complete rookie, because my technique and my reflexes had been distorted. Which is why I deactivated the ARM and learned to rev match myself.
In short, to drive smoothly with the ARM on you must dump the clutch as soon as the gear shift is complete, while not touching the gas pedal at all during this time. Act like an oaf and it will be buttery-smooth.

 

[MrBD1348]

I'm back on the throttle to fast to notice.

If you are new to manual shifting work on your technique and movements/timing and stick to lower rpms until your technique is solid and you've learned your car. You may not be fully disengaging the clutch (i.e. not pressing the pedal far enough.

Then start working on the speed of your shifts. Once you have that nailed, then start shifting at higher revs. These cars build speed too quickly to fool around.

this is what have been doing as of recent. Which is why I feel like I’m now noticing the rev hang more.The speed of my shifts is getting solid enough to make me realize that the rpm not droppingis slowing me down. If that makes sense. I don’t practice at higher rpm for the reason you mentioned.

 

[MrBD1348]

Can't speak for OP but a lot of folks have this issue and complain about excess rev hang. My car does it, too and this isn't some issue unique to inexperienced drivers. Being "quick on the throttle" only exacerbates the rev hang issue as the RPM is mismatched while the revs hang.

this is exactly it. If I’m too quick on the throttle or dump the clutch the moment I know my shift is complete… the car will not be smooth at all

 

[MrBD1348]

Most of the rev hang is caused by the auto rev match. Disabling the ARM will cure that.
There's still a bit of rev hang without the ARM, but that's on par with most other contemporary fuel-injected engines and is quite tolerable. A custom tune can get rid of that, too.


You can, but you must change your technique and use the pedals like someone who's driving for the first time in their life would. It took me a bit of time to get used to it, but in the end I was able to drive extremely smoothly in all situations. The problem was, as soon as I was in a different car I felt like I had forgotten how to drive properly. I was jerking it like a complete rookie, because my technique and my reflexes had been distorted. Which is why I deactivated the ARM and learned to rev match myself.
In short, to drive smoothly with the ARM on you must dump the clutch as soon as the gear shift is complete, while not touching the gas pedal at all during this time. Act like an oaf and it will be buttery-smooth.

I’ll check see if it’s any different without ARM tomorrow. As for custom tune - I already am tuned but as I mentioned the tuner said it’s either on or off for the shift logic. And that most people do not like the car with it turned off.

 

[ice445]

My car only has obnoxious rev hang the first few shifts after a cold start (pretty sure they all do this due to fuel enrichment) and if I'm going WOT, shift, and then let off pretty quick after the shift. It hangs super bad there because it wants to burn all that fuel it expected me to blow through. It's basically an emissions strategy and it can definitely be tuned out. It can also hang on you if you hit any of the torque limiters (clutch, wheel spin, etc) because it will basically lock you out of the throttle for a bit while it burns off that excess fuel.

In normal driving I basically never see any rev hang. With rev matching on, revs fall normally until they are at the correct level for the next gear up. In general it's not perfect, older cars were definitely better about this. But you can get used to it pretty easily.

 

[cerbomark]

I hated the rev hang in my WRX and know it well. I never felt it on my 21 and I have rev match ON.
Your is a 22 so I wonder if the recent changes on the engine (10HP less, etc ) is where the culprit is?
And I don t mean the HP , I mean the changes to cause that, FYI.

 

[PC_GUARD]

Only time I see it in my gen 2 is when I've been getting after it and abort.

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