Clutch Slipping on stock A91 MT...

[BMWAF]

Removing the CDV makes the operation more intuitive - that is to say your brain gets what it expects.

This just clouds things further for me. Intuition isn't a universal concept. I've been driving with a CDV in a Honda for decades and never once thought it was unintuitive or not what my brain expects.

When I find someone local who has had the CDV removed, I'll check it out but otherwise, I'm just not sold.

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[lucky phil]

It's really simple.

Regardless of what happens when you side-step the clutch, the CDV acts as a damper.

The spring pressure you feel comes from the diaphragm spring on the clutch. That spring transmits force hydraulicly to your foot. The clutch delay valve limits the flow of that hydraulic system, and below a certain rate of flow provides almost no limit at all. So while you may feel the same pressure with the clutch pressed to the floor, how much of that pressure persists at your foot will change based on the speed you move your foot.

It is that variability that leads to drivability issues when you switch from driving casually to driving aggressively. Your brain expects the clutch to move a certain way based on the pressure applied or released by your foot, and it gets a result that's unexpected.

Removing the CDV makes the operation more intuitive - that is to say your brain gets what it expects.

Just ignore Phil. He admits he's never tried this. He doesn't speak from first-hand experience. A whole bunch of the rest of us do.

From a technical hydraulic engineering perspective that's not quite true. Any restrictor in a simple hydraulic system will only have an effect when the flow rate is high enough for the restrictor to have an influence. Plenty of systems have restrictors and hydraulic fuses in the system that have zero influence until there is an abnormal flow rate and even then the simple fixed orifice restrictor can be totally benign in normal operation flow rates. So maybe the CDV is in this category. Has no impact on the clutch action under normal clutch operating conditions because the hydraulic flow rate is below the restrictors influence. Side step the clutch or get jerky with the pedal at the friction point and then the restrictor has an influence due to the spiking hydraulic flow rate and dampens the action a little.



Phil

 

[mdpalmer]

Wow 40 pages on clutch slipping...

Makes me wonder if people are finding reasons to complain versus just driving the car. Or maybe the clutch was not properly broken in, I get the sense the average person doesn't understand how important it is to respect that process for something that depends on friction to work properly (brakes, tires for example). But MT Supra owners should know better, right? Sure quality control could be an issue, or maybe it's just a crap design.

In my case, I'm very happy with the car.

Still have CDV in mine, it's not that bad IMO. Initially, I thought something was wrong with my car ? I thought, "why does the clutch feel like this?"

Took some time and deliberate effort getting used to driving the car, the first 1000 miles or so while the drivetrain was broken in was a good time to feel the whole car out.

I daily drive an old Acrua Integra with a manual trans so going back and forth between the cars gave me a basis for comparing the two cars in how they "feel" which is totally subjective, of course.

I have some hard canyon runs on the car and my first track day (4x 20 minute sessions, + a lot of fun to and from the track 180 miles each way, thanks Toyota!) under my belt, and every time I take the car out, once the engine and tires are warmed up I thoroughly enjoy it. No clutch dumps or no lift shifts, tho. Car has rewarded me with nothing but smiles.

I love how this car drives and shifts although I would prefer to not have the subtle delay action of the clutch, I find it to be acceptable for my driving style. I've gotten better at launching the car from a dead stop, which I've found to be the most "delayed" when it comes to clutch engagement. Gear changes up or down, while at speed, are actually pretty awesome in the Supra IMO.

No clutch issues so far, time will tell. When it does go I have no problem replacing it with an aftermarket one with a hydraulic release bearing, etc.

Go out and enjoy the car, if you don't like how the car drives or shifts, sell it. Plenty of ATs and EVs for sale these days.

 

[lucky phil]

Wow 40 pages on clutch slipping...

Makes me wonder if people are finding reasons to complain versus just driving the car. Or maybe the clutch was not properly broken in, I get the sense the average person doesn't understand how important it is to respect that process for something that depends on friction to work properly (brakes, tires for example). But MT Supra owners should know better, right? Sure quality control could be an issue, or maybe it's just a crap design.

In my case, I'm very happy with the car.

Still have CDV in mine, it's not that bad IMO. Initially, I thought something was wrong with my car ? I thought, "why does the clutch feel like this?"

Took some time and deliberate effort getting used to driving the car, the first 1000 miles or so while the drivetrain was broken in was a good time to feel the whole car out.

I daily drive an old Acrua Integra with a manual trans so going back and forth between the cars gave me a basis for comparing the two cars in how they "feel" which is totally subjective, of course.

I have some hard canyon runs on the car and my first track day (4x 20 minute sessions, + a lot of fun to and from the track 180 miles each way, thanks Toyota!) under my belt, and every time I take the car out, once the engine and tires are warmed up I thoroughly enjoy it. No clutch dumps or no lift shifts, tho. Car has rewarded me with nothing but smiles.

I love how this car drives and shifts although I would prefer to not have the subtle delay action of the clutch, I find it to be acceptable for my driving style. I've gotten better at launching the car from a dead stop, which I've found to be the most "delayed" when it comes to clutch engagement. Gear changes up or down, while at speed, are actually pretty awesome in the Supra IMO.

No clutch issues so far, time will tell. When it does go I have no problem replacing it with an aftermarket one with a hydraulic release bearing, etc.

Go out and enjoy the car, if you don't like how the car drives or shifts, sell it. Plenty of ATs and EVs for sale these days.

The "my clutch is slipping" and every MK5 manual clutch is going to blow up and we'll all need an upgrade only lasted for a few pages if memory serves. As is common with these things on forums it all just dissipated as noise eventually does in an internet Eco chamber. No horror stories, blown up clutches warranty arguments, all just peters out. I'm with you after driving manuals all my life it's the best I've ever used. I expected the clutch "feel" to be more like a modern diaphragm spring style pressure plate with a short friction/take up point and lower full travel holding pressure but in fact it feels more like and old style coil spring clutch with a wide take up band and a fairly constant pedal pressure for the whole clutch travel. Unfortunately I don't have a 2023 shop manual with the clutch system so I can't have a look at the pressure plate and flywheel system. No matter to me I'm happy as hell with it and see no need to mess with the clutch or actuation system.

Phil

 

[GRMan]

The clutch is a ‘softie’ on the GR Supra ?

Seriously, the GR86 also has a CDV but still feels like a 90/00’s JDM clutch. It feels quite a bit heavier and more grabbing. The rate of clutch engagement has a direct effect on the smoothness on the ride.

The Supra’s clutch mechanism on the otherhand, doesn’t reward precision. One can totally stuffed up the cluch engagement and the drivetrain will still be happy and won’t give it to your face, no jolt. This is the part where I feel the focus on making the car more driven friendly has ruined (still MT all the way) the manual experience .

The GR86 does a much better job in managing drivetrain protection vhile giving driver’s feedback, ‘you did a great job so I won’t complain’ or ‘you fucked up and I was going to hit you in the face but I have been taught to slap you on the wrist indtead’

 

[BMWAF]

The clutch is a ‘softie’ on the GR Supra ?

Seriously, the GR86 also has a CDV but still feels like a 90/00’s JDM clutch. It feels quite a bit heavier and more grabbing. The rate of clutch engagement has a direct effect on the smoothness on the ride.

The Supra’s clutch mechanism on the otherhand, doesn’t reward precision. One can totally stuffed up the cluch engagement and the drivetrain will still be happy and won’t give it to your face, no jolt. This is the part where I feel the focus on making the car more driven friendly has ruined (still MT all the way) the manual experience .

The GR86 does a much better job in managing drivetrain protection vhile giving driver’s feedback, ‘you did a great job so I won’t complain’ or ‘you fucked up and I was going to hit you in the face but I have been taught to slap you on the wrist indtead’

I much prefer Honda's Type R approach: You get it right, you get rewarded with silky smooth speed. You fuck it up, you go slow bitch.

It really forces you to up your manual game and its fun improving every time you go for a drive.

 

[BananaBoi]

Jumping in on this thread to say at at 11k miles, mine has started slipping as well.

Was going to pass someone on the highway and my RPM started floating around 5-6k in 6th gear despite going like 75mph.

I know its not user error cause I've only ever owned manual cars and I don't beat on the car either since its my DD. Car is stock except for intake. Built in September 2023.

I talked to my dealership and its $300-400 to diagnose, determine cause, and see if it'll be covered under warranty.

 

[DC5UPRA]

Jumping in on this thread to say at at 11k miles, mine has started slipping as well.

Was going to pass someone on the highway and my RPM started floating around 5-6k in 6th gear despite going like 75mph.

I know its not user error cause I've only ever owned manual cars and I don't beat on the car either since its my DD. Car is stock except for intake. Built in September 2023.

I talked to my dealership and its $300-400 to diagnose, determine cause, and see if it'll be covered under warranty.

Keep us updated if you do take it and what they find.

 

[RenRed2]

The "my clutch is slipping" and every MK5 manual clutch is going to blow up and we'll all need an upgrade only lasted for a few pages if memory serves. As is common with these things on forums it all just dissipated as noise eventually does in an internet Eco chamber. No horror stories, blown up clutches warranty arguments, all just peters out. I'm with you after driving manuals all my life it's the best I've ever used. I expected the clutch "feel" to be more like a modern diaphragm spring style pressure plate with a short friction/take up point and lower full travel holding pressure but in fact it feels more like and old style coil spring clutch with a wide take up band and a fairly constant pedal pressure for the whole clutch travel. Unfortunately I don't have a 2023 shop manual with the clutch system so I can't have a look at the pressure plate and flywheel system. No matter to me I'm happy as hell with it and see no need to mess with the clutch or actuation system.

Phil

Best post here on this thread. The drivers testing these are setting amazing times for the publications or websites without the CDV being removed. Lets just leave it that. The CDV removal is not a solution to poor driving skills or use beyond the system's ability. What it appears to be in a placebo effect found on forums.

 

[BMWAF]

The drivers testing these are setting amazing times for the publications or websites without the CDV being removed. Lets just leave it that.

Not really. The drivers setting these times couldn't give two shits about the cars they test. They're probably flat shifting and generally bashing the shit out of the transmission (and rest of the car). I mean, sure.. they might extract magical times, but at what cost?

The CDV removal is not a solution to poor driving skills or use beyond the system's ability. What it appears to be in a placebo effect found on forums.

While I am the first to agree with the belief that the majority of manual transmission issues people are having are essentially user error, there is something definitely wrong with the 1-2 shift - at least in my particular car.

I've also been quite vocal at denouncing the CDV delete solution but (perhaps ironically) have recently had my CDV deleted. I haven't had enough time in the seat to make a call on it, but my first impression isn't negative.

I'll report back once I'm confident of my experiences.

 

[Stvee]

I've also been quite vocal at denouncing the CDV delete solution but (perhaps ironically) have recently had my CDV deleted. I haven't had enough time in the seat to make a call on it, but my first impression isn't negative.

I'll report back once I'm confident of my experiences.

It takes a hundred miles or so to readjust your brain since the difference is that pronounced.

 

[lucky phil]

It takes a hundred miles or so to readjust your brain since the difference is that pronounced.

Seriously? A hundred miles to figure out what is supposedly the best/ultimate mod you can do to a manual Supra. Like I've said before there many mods made that certainly make things feel "different" but different doesn't always mean better it can just means "different".

Phil

 

[Stvee]

Seriously? A hundred miles to figure out what is supposedly the best/ultimate mod you can do to a manual Supra. Like I've said before there many mods made that certainly make things feel "different" but different doesn't always mean better it can just means "different".

Phil

Your opinion on the subject is irrelevant until you've experienced both setups side by side. It is hands down far better after the removal of the CDV. Notice how you won't find anyone saying the opposite that has actual experience with both.

There is nothing to "figure out", it just takes your brain a bit to readjust to how different the clutch feels when you're used to it feeling another way.

 

[BMWAF]

Seriously? A hundred miles to figure out what is supposedly the best/ultimate mod you can do to a manual Supra. Like I've said before there many mods made that certainly make things feel "different" but different doesn't always mean better it can just means "different".

Phil

Notice how you won't find anyone saying the opposite that has actual experience with both.

I honestly can't make a solid comment just yet - I literally drove the car home and then to the PPF shop a few days later. I can say that it did feel a little different out of the box. Not particularly better but also not worse. Just different. Not wildly different, mind you but I want to say, more direct maybe?

My Honda has a CDV in it and not once in 16 years have I contemplated removing it! In my Supra, the 1-2 shift is just unreliable and that's my only reason for trying the somewhat infamous CDV delete.

If the weather clears up I'll take her for a decent run on the weekend and hopefully be closer to being able to provide a more useful take on this modification.

 

[Stvee]

It being more direct and more consistent is the entire point of removing it. It's not going to make a huge difference in clutch longevity or anything but it will absolutely improve the clutch feel.

I agree that CDVs in some other manufacturers aren't necessarily bad but they are obnoxious in BMWs.

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