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Old 09-12-2014, 12:12 AM   #1
typicalman1
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Default 2015 WRX rev hang issue

Okay, I think I've done enough search for 2015 WRX rev hang problem.
Seems like majority of 2015 WRX manual transmission owners are experiencing
this rev hang that causes jerky shift from 1st to 2nd gear.

"Rev hang" in 2015 WRX context is your engine rpm not dropping immediately(rpm stays there for 1.5 sec or so)
after you disengaging clutch when shifting between gears (1st to 2nd, and 2nd to 3rd gear is most noticeable. Unnoticeable 3rd gear and up).
This causes a very jerky shifting because in between shifting gears, engine rpm has to drop immediately/fast enough
so that it will accommodate higher gears.

For example, talking about shifting,
at 3,000rpm, 1st gear gives 15mph - then you shift into 2nd gear
at 15mph in 2nd gear, rpm should be at 2,000rpm

If engine rpm does not drop from 3,000rpm to 2,000rpm during your shifting process
(push down clutch, shift gear, and engage clutch again), there will be difference
in rotational speed in between your engine and transmission,
and this causes "shock" in your car's drivetrain.

Why is that? because at 3,000rpm, car in 2nd gear should be running at 25mph, but your
current speed is only 15mph. This 10mph/1,000rpm difference in rotational speed is absorbed by
your car's drivetrain with "shock".

You can also search in youtube and see some videos there (Civic SI too had the same issue).
Apparently this rev hang is designed by engineers to meet emission requirement (to burn fuel completely)
and is programmed in your car's ECU. My opinion is, whatsoever of emission requirement, manual transmission
car has to drive like it should be, without compromising car's longevity and owner's driving pleasure.

So many people driving 2015 manual have brought up "jerky shifting", "difficult to shift smoothly" and I too,
thought it was my driving skill and tried to keep hone my shifting - but it was not. It was rev hang.

I do not know if Subaru is addressing this issue yet, but if we bring it up constantly and make it viral, they
will fix it. Because if negative reputation gets big enough it will affect their sales, and that's when
companies/corporations act.

Welcome any feedback, comment, and opinions.
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Last edited by typicalman1; 09-13-2014 at 12:55 PM.
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Old 09-12-2014, 12:15 AM   #2
psyclobe
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I was told by my local tuner that the reason for the rev hang is to ensure a smoother shift into second (Gets the syncros up to speed more likely is the idea (easier on the transmission?)).

He also mentioned that when he tuned the Ford Focus ST, that there was a way to adjust that hang in the ECU.
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Old 09-12-2014, 12:18 AM   #3
Napalm3nema
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sounds like nany tech to protect princess from trashing her synchros when she can't drive properly.
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Old 09-12-2014, 12:22 AM   #4
thill
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I seriously doubt Subaru will do anything about this. Getting a pro tune or a Cobb tune, etc fixes it.
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Old 09-12-2014, 12:29 AM   #5
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Quote:
Originally Posted by thill View Post
I seriously doubt Subaru will do anything about this. Getting a pro tune or a Cobb tune, etc fixes it.
Really? I haven't heard or seen anyone with a tune talking about it fixing this. I've read that some OTS tuners are working on it, but haven't heard of any of them that solved it already.

Are you sure it fixes it?

I should add that I experience zero rev hang. What I experience is an extremely slow rev down. The rpms start falling as soon as I disengage the clutch, but it takes way too long to fall down to the appropriate rpm for the next gear up, forcing me to either wait 2-3 seconds to engage 2nd gear after coming out of 1st, or shift at a normal speed and put shock on my drive train as well as unnecessary wear on my clutch and flywheel.
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Old 09-12-2014, 12:52 AM   #6
typicalman1
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Quote:
Originally Posted by psyclobe View Post
I was told by my local tuner that the reason for the rev hang is to ensure a smoother shift into second (Gets the syncros up to speed more likely is the idea (easier on the transmission?)).

He also mentioned that when he tuned the Ford Focus ST, that there was a way to adjust that hang in the ECU.
As far as my knowledge, there is no tuner yet to fix 2015 WRX rev hang problem. Someday tuners will be able to figure it out - but it will void warranty.

And what your local tuner said about rev hang ensuring a smoother shift with synchros and all, I think he's wrong. I do not know if you have a car with rev hang issue, but regardless you can think about it when you drive your manual car next time.
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Old 09-12-2014, 02:05 AM   #7
jmwoz11
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I heard it was an emissions thing or something like that. It doesn't make any sense to me, but i have no knowledge in that area.
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Old 09-12-2014, 03:05 AM   #8
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The cobb accessport completely removes this issue and I love it for daily driving.
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Old 09-12-2014, 09:04 AM   #9
psyclobe
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Quote:
Originally Posted by WARDlock View Post
The cobb accessport completely removes this issue and I love it for daily driving.
Odd, I have an accessport and I still have the rev hang issue...

I also just got a protune, and when I pick it up today, I'm sure it will still be there.
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Old 09-12-2014, 09:18 AM   #10
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I've never noticed it... I guess I can continue to sleep at night.
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Old 09-12-2014, 10:11 AM   #11
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Quote:
Originally Posted by Wireeater View Post
I've never noticed it... I guess I can continue to sleep at night.
I don't know how that's possible. It is so brutally, painfully obvious going from 1st to second. If I hold 1st up to 5k, disengage clutch for a normal speed shift, I can count to just past 2 seconds before the RPM drops to 3k. God forbid you're trying to make a quick 1-2 shift, you just have to let the clutch pull the engine speed down and deal with the harsh engagement.
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Old 09-12-2014, 10:15 AM   #12
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This is not an issue, most new cars have this built in.
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Old 09-12-2014, 10:24 AM   #13
thill
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Quote:
Originally Posted by Minioner View Post
Really? I haven't heard or seen anyone with a tune talking about it fixing this. I've read that some OTS tuners are working on it, but haven't heard of any of them that solved it already.

Are you sure it fixes it?

I should add that I experience zero rev hang. What I experience is an extremely slow rev down. The rpms start falling as soon as I disengage the clutch, but it takes way too long to fall down to the appropriate rpm for the next gear up, forcing me to either wait 2-3 seconds to engage 2nd gear after coming out of 1st, or shift at a normal speed and put shock on my drive train as well as unnecessary wear on my clutch and flywheel.
Some folks with a Cobb tune said it fixed the issue.
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Old 09-12-2014, 10:35 AM   #14
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Quote:
Originally Posted by Ultimateone View Post
This is not an issue, most new cars have this built in.
I think you mean it is intended? It is most certainly an issue, intention doesn't make a difference when something breaks the driving experience.
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Old 09-12-2014, 11:21 AM   #15
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Quote:
Originally Posted by Minioner View Post
I think you mean it is intended? It is most certainly an issue, intention doesn't make a difference when something breaks the driving experience.
It's not an issue. It's a characteristic of modern emission controls that enthusiasts don't like. Manufacturers employ rev hang to lessen blow by emissions from immediately closing the throttle body. It lengthens the life of the Catalytic converter from lessening the amount of unburned fuel contamination. It also helps keeping crankcase pressures down on turbocharged cars as when accelerating at full boost then abruptly closing the throttle to change gears causes high crankcase pressure and oil blow-by.
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Old 09-12-2014, 02:15 PM   #16
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Quote:
Originally Posted by heavyD View Post
It's not an issue. It's a characteristic of modern emission controls that enthusiasts don't like. Manufacturers employ rev hang to lessen blow by emissions from immediately closing the throttle body. It lengthens the life of the Catalytic converter from lessening the amount of unburned fuel contamination. It also helps keeping crankcase pressures down on turbocharged cars as when accelerating at full boost then abruptly closing the throttle to change gears causes high crankcase pressure and oil blow-by.
It might lengthen the catalytic converter but at the same time it is reducing longevity of drive terrain (affected engine parts, clutch, transmission). What is more difficult to replace in terms of effort and price? I don't know how much catalytic converter costs but clutch alone should cost around $1,600. Not to mention transmission, etc.
You are also saying rev hang protects crankcase when accelerating at full boost, but who does full boost accelerating in the 1st gear? If that is even possible, how often do people do that?

Rev hang does affect everyday driving experience like a crap.
People driving older models think it's none of their business,
but in fact,they will be experiencing the same thing in the future,
sooner or later, because their current cars won't last forever.
This should be something every manual car driver should be
alerted for, especially if all manufacturers are going to make
cars like this going forward.
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Old 09-12-2014, 07:49 PM   #17
sajakh
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I have the access port with the latest OTS cobb tune v 109 and I still have the rev hang. I HATE IT. It makes getting up to speed very annoying whether it is at a relaxed pace or at max acceleration.

Cobb needs to fix this ASAP!
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Old 09-12-2014, 08:24 PM   #18
typicalman1
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Quote:
Originally Posted by sajakh View Post
I have the access port with the latest OTS cobb tune v 109 and I still have the rev hang. I HATE IT. It makes getting up to speed very annoying whether it is at a relaxed pace or at max acceleration.

Cobb needs to fix this ASAP!
no. Subaru has to fix it. Doesn't hooking up Access Port voids your warranty?
Civic SI had the same rev hang issue and I heard Honda came up with ECU flash to remove(or alleviate) the hang. Of course Honda didn't do that proactively. After all that virals, complaints in forums, youtube videos, etc Honda finally came up with something to address the problem. I'm surprised how 2015 WRX owners are so quite about this. There is no video on youtube talking about this problem. We have to make this a big deal.
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Old 09-12-2014, 08:50 PM   #19
2015WRXRed
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I dare wrx owners to have the cajones to make subaru release an ecu fix
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Old 09-12-2014, 08:57 PM   #20
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Originally Posted by 2015WRXRed View Post
I dare wrx owners to have the cajones to make subaru release an ecu fix
My rev hang issue is documented with Subaru. That said, if Subaru says that this behavior is for emissions control reasons, nothing will ever be done by Subaru (cajones or no).

I actually think that Cobb is more likely to have a fix for this, but the accessport will be a problem with warranty.
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Old 09-12-2014, 09:40 PM   #21
minuccims
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My 2010 LGT has the same issue. Much worse stock. Pro-Tune was better because of throttle control mapping. However the tune did not change the slow drop of rpms for the initial second. You have a choice to rev match and avoid the rpm annoyance.

Last edited by minuccims; 09-12-2014 at 10:05 PM.
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Old 09-12-2014, 10:01 PM   #22
typicalman1
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Originally Posted by daverup View Post
My rev hang issue is documented with Subaru. That said, if Subaru says that this behavior is for emissions control reasons, nothing will ever be done by Subaru (cajones or no).

I actually think that Cobb is more likely to have a fix for this, but the accessport will be a problem with warranty.
what do you mean you got your issue documented with Subaru? You filed a complaint with your Subaru dealer? What was their reaction?
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Old 09-12-2014, 10:04 PM   #23
typicalman1
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Originally Posted by minuccims View Post
My 2010 LGT has the same issue. Much worse stock. Pro-Tune was better because of throttle control mapping. However the tune did not change the slow drop of TPMS for the initial second. You have a choice to rev match and avoid the rpm annoyance.
Rev hang has nothing to do with rev matching.
You can't fix anything with rev matching when rpm is not dropping fast enough.
And btw, what does TPMS have to do with slow dropping? you mean rpm?
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Old 09-12-2014, 10:06 PM   #24
minuccims
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Yup, rpm, spell checker hell
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Old 09-12-2014, 10:22 PM   #25
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Quote:
Originally Posted by typicalman1 View Post
what do you mean you got your issue documented with Subaru? You filed a complaint with your Subaru dealer? What was their reaction?
I reported the rev hang between shifts to my Subaru dealer service dept on more than one regular service appointment. I don't have access to that receipt at the moment, but there is a documented issue reported to the Subaru Service Techs that the dealership techs go to when they don't have answers.
It's just an open service case of some sort.
The dealership techs can't do anything but report it, that is what they did. I'm happy with the local techs, not really expecting anything from Subaru.
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