COBB vs Mountune for eliminating Shift Assist / Rev Hang

[SirThomas88]

Don't wanna knock your driving experience here buddy but in any normal manual car if you up-shift too quickly the clutch will be used to pull down the revs from lets say 3rd to 4th. "Quickly" is 100% defined by how fast the revs fall. Ideally, when you up shift, the time it takes you to move the stick from one gear to the next is exactly how long it takes the revs to fall to rev-match into the next gear. This is not the case in the Fiesta in ANY gear. There's no single gear change in this car that you can do in a timely manner. You're always waiting for the revs to fall. 1st -> 2nd. 2nd -> 3rd. 3rd -> 4th. You always shift the stick faster than the revs can fall. That means you're always waiting for the car's revs to catch up. This is just poor design on Ford's part. And every time you wanna drive fast you have to burn out your clutch or lose momentum waiting for the revs to fall. Anyone who thinks this isn't a huge issue either doesn't have the issue, doesn't understand the issue, or doesn't know what the issue is. I'm not crazy and I'm willing to sell the car at a huge loss because it's so bad.

I have to agree with this sentiment completely. Though I won't sell the car, I am really looking forward to replacing the flywheel, I hope that will help.

#2 is that the dual mass flywheel has springs that dampen some engine vibration so that it doesn't reach the transmission and create lash in the transmission itself. It also absorbs some of the difference in rotation speed between the crank and input shaft when you shift, so while the weight can make the revs fall slower, the springs help reduce the impact of it.

Is this transmission lash a significant concern for causing damage in these transmissions with a lightweight flywheel? If so, will definitely make me think twice about installing a lightweight flywheel, which would be a huge bummer!!

 

[92083420938420]

$3000 rebates on '17's, which seem to be in huge numbers of what's available, and $2000 on '18's which literally only adds rear camera... Or, super low interest on either model instead if you qualify.. But ya, mostly '17's getting bigger discounts on top of just the rebate, it's quite easy to get one for $4000 under MSRP... I traded in a Forte5 SX for mine with a very similar motor and the Kia also had more rev hang than I was used to at first, but either the ECU, or you as the driver, learns, but it does get better in time.

Unfortunately it doesn't get better with time because the main culprit is the flywheel is a physical issue. Either you burn out your clutch excessively in small amounts per shift pulling the revs down faster by slowly releasing the cluth or you burn the cluth out massively by dropping it on up shifts and yanking the revs down.

For now I'll keep my car for sale and wait it out and I'll see if getting a new flywheel is worth it and enough of a fix to make the car worth keeping.

Again, this shouldn't be an issue. Driving dynamics in a manual car should absolutely be #1 front and center. Instead it's #3 in the Fiesta behind saving the environment and helping newer manual drivers I guess.

I have to agree with this sentiment completely. Though I won't sell the car, I am really looking forward to replacing the flywheel, I hope that will help.


Is this transmission lash a significant concern for causing damage in these transmissions with a lightweight flywheel? If so, will definitely make me think twice about installing a lightweight flywheel, which would be a huge bummer!!

I might just go all-in and swap it out. I don't think the lash will be a significant issue. I think the dampening in the stock flywheel is more for anti-stall and smoothness. People are running stock transmissions approaching 300HP without an issue so it seems to be well engineered.

 

[danbfree]

Unfortunately it doesn't get better with time because the main culprit is the flywheel is a physical issue. Either you burn out your clutch excessively in small amounts per shift pulling the revs down faster by slowly releasing the cluth or you burn the cluth out massively by dropping it on up shifts and yanking the revs down.

For now I'll keep my car for sale and wait it out and I'll see if getting a new flywheel is worth it and enough of a fix to make the car worth keeping.

Again, this shouldn't be an issue. Driving dynamics in a manual car should absolutely be #1 front and center. Instead it's #3 in the Fiesta behind saving the environment and helping newer manual drivers I guess.



I might just go all-in and swap it out. I don't think the lash will be a significant issue. I think the dampening in the stock flywheel is more for anti-stall and smoothness. People are running stock transmissions approaching 300HP without an issue so it seems to be well engineered.

Not sure how that really is much of an issue regarding the clutch life, 95% of manual drivers don't bother with rev matching/heel-toe or any of that, I still expect the clutch to last 80-100k... it also doesn't really affect the fun of the car unless you let that rev hang bother you knowing the clutch won't last 200k, but to each their own, fair enough!

Sent from my SM-G930P using Tapatalk

 

[stascom]

I have the non-MP215 Mountune in the '17. It's definitely better than stock. I like to run 2nd to the red line and upshift to 6th on short on-ramps. At stock it took about 4-5sec for the RPMs to match up (I double clutch to speed this up). With MT it's about half the time. Still pretty laggy. I can't get used to it because I also have a 350z with a light flywheel. Switching back and forth is night and day. Interestingly enough, the most responsive throttle I've experienced was in the 1st gen Scion xB that the FiST has replaced. Those cars run a 3-decade old engine design with a throttle cable and a factory cold air intake. It revved like a go-kart; felt telepathic, like the engine crank was the extension of my foot. I miss that. No cars will ever be made like that again. Hell, they haven't been for over a decade.

 

[DaveG99]

Why would you want the Rpm's to fall? Keeping them up is better for performance.

 

[danbfree]

I have the non-MP215 Mountune in the '17. It's definitely better than stock. I like to run 2nd to the red line and upshift to 6th on short on-ramps. At stock it took about 4-5sec for the RPMs to match up (I double clutch to speed this up). With MT it's about half the time. Still pretty laggy. I can't get used to it because I also have a 350z with a light flywheel. Switching back and forth is night and day. Interestingly enough, the most responsive throttle I've experienced was in the 1st gen Scion xB that the FiST has replaced. Those cars run a 3-decade old engine design with a throttle cable and a factory cold air intake. It revved like a go-kart; felt telepathic, like the engine crank was the extension of my foot. I miss that. No cars will ever be made like that again. Hell, they haven't been for over a decade.

Interesting, the '17 I just bought the rev hang is only 1 second max or maybe it's more in full RPM runs, or more to *fully* match up is what you mean, but doesn't really seem to affect anything performance related other than possibly clutch life slightly...

 

[stascom]

Interesting, the '17 I just bought the rev hang is only 1 second max or maybe it's more in full RPM runs, or more to *fully* match up is what you mean, but doesn't really seem to affect anything performance related other than possibly clutch life slightly...

Yes, I meant full rev match. I don't care about clutch life. It makes the shift jerky as you first send the engine into forced deceleration, when clutching out early, and then into acceleration when the throttle reverses the RPM drop, so you get drivetrain backlash like a noob.

 

[danbfree]

Yes, I meant full rev match. I don't care about clutch life. It makes the shift jerky as you first send the engine into forced deceleration, when clutching out early, and then into acceleration when the throttle reverses the RPM drop, so you get drivetrain backlash like a noob.

Interesting, I just came from another modern 6-speed manual compact and this Fiesta is worlds smoother, TIL it's really not... LOL.

 

[danbfree]

Yes, I meant full rev match. I don't care about clutch life. It makes the shift jerky as you first send the engine into forced deceleration, when clutching out early, and then into acceleration when the throttle reverses the RPM drop, so you get drivetrain backlash like a noob.

Interesting, I just came from another modern 6-speed manual compact and this Fiesta is worlds smoother, TIL it's really not... LOL.

 

[MauiRoads]

Rev-hang is real! I appreciate 92083420938420 breaking it down into 3 possible meanings. It seems that No. 2 Shift Assist can be tuned out or reduced. It's No.3 that is unusually bad in the ST and legitimately a problem. That's what I've always thought of as rev-hang. After releasing the throttle, the revs drop very slowly. It takes longer for the revs to drop than it takes to shift, so, you are now re-engaging the clutch at revs that are higher than the rev-match rpm. This means that clutch slip is being used to slow the engine to the correct rpm for the gear change...along with a jerk/thunk through the driveline.

Obviously, it would be better if this did not happen. Yes, some don't care about the clutch wear, driveline shock and jerky shifts. I do care. I rev-match downshifts for those reasons (and to maintain traction at the limit when trail-braking) and I don't think I should have to rev-match up-shifts, by waiting several seconds between gears.

I know "rev-match" is a term usually related to down-shifting, but revs should also match on upshifts. Usually, there's no issue because the revs drop fast enough to be at the matching/correct rpm when engaging the next higher gear.

I just bought a 2018 ST and I love the car, EXCEPT the rev-hang is the worst I've ever seen. As you can see from my profile photo, I have a 2006 NC Miata: minor rev-hang. I've also owned Porsche, BMW, Lotus, Toyota, VW, Nissan and other Mazdas, and driven many other cars. Never had anything near this problem. My nephew's 05 Civic had rev-hang, and his 18 Kia has it, but nothing like the ST. In the ST, it can take multiple seconds to drop from a shift at 4000 rpm, down to the 2000 rpm rev match for the next higher gear.

Of course, the weight of the flywheel matters. That's physics. But how much of the ST's problem is the flywheel? I don't think it's the largest factor, and here's why. If it were just the flywheel, the rate of rev-drop would be linear. It's not. And it would be consistent in shifts between all gears and in neutral. It's not. In the rpm range (for example 4000 down to 2000 rpm) of a rev-drop, it drops faster at some points and slower at others. That's not physics, and has to be software. I look forward to hearing from anyone who installed a lighter flywheel, and how much it affected the rev-hang.

I will experiment and report back, hopefully with video. If nothing else, a comparison of a neutral rev-drop vs. an up-shift rev-drop should tell us a lot.

I've researched but cannot find that this problem has been solved by a tune...yet. Maybe a tuner can be persuaded to solve it. I think they'd sell a lot of tunes.

 

[FiestaSTdude]

Rev-hang is real! I appreciate 92083420938420 breaking it down into 3 possible meanings. It seems that No. 2 Shift Assist can be tuned out or reduced. It's No.3 that is unusually bad in the ST and legitimately a problem. That's what I've always thought of as rev-hang. After releasing the throttle, the revs drop very slowly. It takes longer for the revs to drop than it takes to shift, so, you are now re-engaging the clutch at revs that are higher than the rev-match rpm. This means that clutch slip is being used to slow the engine to the correct rpm for the gear change...along with a jerk/thunk through the driveline.

Obviously, it would be better if this did not happen. Yes, some don't care about the clutch wear, driveline shock and jerky shifts. I do care. I rev-match downshifts for those reasons (and to maintain traction at the limit when trail-braking) and I don't think I should have to rev-match up-shifts, by waiting several seconds between gears.

I know "rev-match" is a term usually related to down-shifting, but revs should also match on upshifts. Usually, there's no issue because the revs drop fast enough to be at the matching/correct rpm when engaging the next higher gear.

I just bought a 2018 ST and I love the car, EXCEPT the rev-hang is the worst I've ever seen. As you can see from my profile photo, I have a 2006 NC Miata: minor rev-hang. I've also owned Porsche, BMW, Lotus, Toyota, VW, Nissan and other Mazdas, and driven many other cars. Never had anything near this problem. My nephew's 05 Civic had rev-hang, and his 18 Kia has it, but nothing like the ST. In the ST, it can take multiple seconds to drop from a shift at 4000 rpm, down to the 2000 rpm rev match for the next higher gear.

Of course, the weight of the flywheel matters. That's physics. But how much of the ST's problem is the flywheel? I don't think it's the largest factor, and here's why. If it were just the flywheel, the rate of rev-drop would be linear. It's not. And it would be consistent in shifts between all gears and in neutral. It's not. In the rpm range (for example 4000 down to 2000 rpm) of a rev-drop, it drops faster at some points and slower at others. That's not physics, and has to be software. I look forward to hearing from anyone who installed a lighter flywheel, and how much it affected the rev-hang.

I will experiment and report back, hopefully with video. If nothing else, a comparison of a neutral rev-drop vs. an up-shift rev-drop should tell us a lot.

I've researched but cannot find that this problem has been solved by a tune...yet. Maybe a tuner can be persuaded to solve it. I think they'd sell a lot of tunes.

If you have an Accessport, I would highly recommend that you get a tune from one of the major fiesta ST tuners. I went with dizzy tuning and it feels much better than stock. That was actually one of the things that motivated me to go with a custom tune.

 

[BrewBean]

I had the "rev assist" disabled by my tuner, and I barely noticed a difference.

The dual mass flywheel in my fist is making an absolute racket. Ford diagnosed it as the dmf going bad, but does not necessitate replacement... yet.

Likely going to go with a Spec single mass flywheel paired with their least aggressive sprung clutch. Kill 2 birds with one stone.

 

[92083420938420]

I had the "rev assist" disabled by my tuner, and I barely noticed a difference.
Likely going to go with a Spec single mass flywheel paired with their least aggressive sprung clutch.

Sold my fiesta years ago because of the rev hang but still following the car closely. I'd love to hear if the flywheel fixes the issue for you or not after you get it done.

I will experiment and report back, hopefully with video. If nothing else, a comparison of a neutral rev-drop vs. an up-shift rev-drop should tell us a lot.

I've researched but cannot find that this problem has been solved by a tune...yet. Maybe a tuner can be persuaded to solve it. I think they'd sell a lot of tunes.

It's refreshing to hear from another person who not only understands the core issue but also the severity of it. Let me know if you find any way to mitigate or even better fix the issue. I'd love to get back into a FiST.

 

[Mycooking]

I've had hardly any rev hang in my 2017 not sure if its the tune its on or on top of other items the previous owner did, possible fly wheel replacement as it does rev incredibly quickly to red line compared to FiSTs I test drove in the past. I can definitely understand the frustrations with rev hang though.

 

[MauiRoads]

Being new to the St, I've now paid closer attention to the rev-hang and shift-assist symptoms.

I see that shift-assist assumes you are upshifting (not downshifting) and rev-matches the upshift. With the clutch in, the rpm will stay rev-matched for about 2 seconds, then drop to idle. So, it seems that shift-assist's pause at the rev-matched rpm shouldn't affect quick shifting. The upshift rev-match rpm is the same when shifting quickly or slowly. The problem is the how slowly (rev-hang) the rpm drops to the shift-assist rev-matched rpm.

Hopefully shift-assist 's rpm drop is not separately programmed to be slow, in addition to a general rev-hang issue. I'll see if my Cobb Accessport allows me to deactivate shift assist, and see if it helps overall rev-hang. I'm still betting that the overall rev-hang issue is mostly tuning, and much less due to the heavy flywheel.

Tuners, any input here??????????? Does the OEM tune include rev-hang, and can it be tuned out?

 

[Dialcaliper]

Being new to the St, I've now paid closer attention to the rev-hang and shift-assist symptoms.

I see that shift-assist assumes you are upshifting (not downshifting) and rev-matches the upshift. With the clutch in, the rpm will stay rev-matched for about 2 seconds, then drop to idle. So, it seems that shift-assist's pause at the rev-matched rpm shouldn't affect quick shifting. The upshift rev-match rpm is the same when shifting quickly or slowly. The problem is the how slowly (rev-hang) the rpm drops to the shift-assist rev-matched rpm.

Hopefully shift-assist 's rpm drop is not separately programmed to be slow, in addition to a general rev-hang issue. I'll see if my Cobb Accessport allows me to deactivate shift assist, and see if it helps overall rev-hang. I'm still betting that the overall rev-hang issue is mostly tuning, and much less due to the heavy flywheel.

Tuners, any input here??????????? Does the OEM tune include rev-hang, and can it be tuned out?

Not a tuner, but the OEM tune includes the hang, as do the COBB OTS tunes

But it looks like Dizzy and Stratified both offer the option to disable it on their Flash tunes.

 

[jmrtsus]

I guess the MP-215 cured the ills described here. No problem with fast shifts ever with my car.......my daughter drove my MP-215 this week and says it shifts better then her stock FiST. Just replaced fluid with OEM still same smooth gear changes. My best manual was an older BMW 320Si also with a Getrag like the FiST. This tranny shifts so smooth it seems like an auto to passengers. Unfortunately lots of people drive manuals but not lots drive one correctly.

 

[tri-pedaler]

Sold my fiesta years ago because of the rev hang but still following the car closely. I'd love to hear if the flywheel fixes the issue for you or not after you get it done.



It's refreshing to hear from another person who not only understands the core issue but also the severity of it. Let me know if you find any way to mitigate or even better fix the issue. I'd love to get back into a FiST.

What did you get to replace the fist?

 

[tri-pedaler]

Being new to the St, I've now paid closer attention to the rev-hang and shift-assist symptoms.

I see that shift-assist assumes you are upshifting (not downshifting) and rev-matches the upshift. With the clutch in, the rpm will stay rev-matched for about 2 seconds, then drop to idle. So, it seems that shift-assist's pause at the rev-matched rpm shouldn't affect quick shifting. The upshift rev-match rpm is the same when shifting quickly or slowly. The problem is the how slowly (rev-hang) the rpm drops to the shift-assist rev-matched rpm.

Hopefully shift-assist 's rpm drop is not separately programmed to be slow, in addition to a general rev-hang issue. I'll see if my Cobb Accessport allows me to deactivate shift assist, and see if it helps overall rev-hang. I'm still betting that the overall rev-hang issue is mostly tuning, and much less due to the heavy flywheel.

Tuners, any input here??????????? Does the OEM tune include rev-hang, and can it be tuned out?

Interesting stuff. Compared to other manual hatches of this era, the rev hang on the Ford is quite mild. I drove a Mazda 3 and Honda Si before this and the rev hang was incredibly bad. For this car, it really only gets in the way for me in quick upshifts at higher revs, where there is a bigger rpm gap between the gears.

Also drive an old ‘53 MG, and you have to blip for every upshift 🙃

 

[92083420938420]

But it looks like Dizzy and Stratified both offer the option to disable it on their Flash tunes.

I'm seeing "shift assist" / "rev hang" explicitly mentioned on dizzy's website for the tune: https://dizzytuning.com/collections...-st-stage-1-flash-tune?variant=32088462426166

But not on the Stratified ST tune site: https://www.stratifiedauto.com/index.php?main_page=product_info&cPath=117_123&products_id=296

I guess the MP-215 cured the ills described here. No problem with fast shifts ever with my car

I'm not seeing any references to shift assist or rev hang anywhere on the MP-215 website nor in any of the reviews for the tune itself on their website. Not saying it doens't help - I just want to catalog as much information as I can in this thread to help reach a resolution.
https://www.mountuneusa.com/Fiesta-St-Mp215-Performance-Upgrade-p/2364-215-aa.htm

What we need at this point is for someone who is experiencing the issue significantly to get the Dizzy tune it seems. I would throw $50 to someone if they were willing to video the issue beforehand, grab an accessport and a dizzy tune, and then video their impressions afterwards to show the issue is gone.

@MauiRoads let me know what your research yields and how I can help. Also can you reach out to Dizzy potentially about rev hang since you already have an accessport? Can't wait to get back into an Orange Spice FiST!