DIY Clutch Delay Valve (CDV) Removal

[pk8]

It's for the brakes themselves. Clutch shares the same fluid.

Get a turkey baster syringe thingy and keep it with the bleeder in the box so you can suck some fluid out if it gets too full after the job if needed. I keep everything in the box to help keep it clean.

Got it. So it serves a different purpose. I still feel they needed clear instructions on operating. Would of saved my a lot of headache, but maybe it is just me.

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[BMWAF]

Hey BMWAF,
Before any knowlege on what a CDV was, I have had problems with the 1-2 gear shift, and it seems others have had the same problem. I had grown so frustrated with this over the last couple months that I started to question whether I should of just gotten the automatic unlocked ECU supra instead (which was available for cheaper when I bought the manual). After I completed the CDV delete, my problems with the 1-2 shift stutter has completely alleviated. At this point, I don't think it is a placebo and it seems others have the same experience.

On the other hand, I actually read some of your earlier post regarding the auto rev matching while upshifting and experimented with turning it on and off. I thought turning it off did help in the beginning but started to have problems again. I actually don't think the auto rev match solves the 2nd gear stutter and is more a placebo in my head ?.

Yeah, I don't even know. ? I turned the rev matching off a few days ago (again) and haven't had a problem since. Personally I think its software - Probably related to the throttle hesitation some people have also experienced. Maybe switching rev matching on/off resets it in some way for a while. Who knows?

When I first had the CDV removed I also thought it was better but after a while felt it was pretty much the same. I think the bottom line is that it's just a very ordinary manual transmission implementation.. or maybe in some cases, just Friday built. ?‍

 

[lucky phil]

Yeah, I don't even know. ? I turned the rev matching off a few days ago (again) and haven't had a problem since. Personally I think its software - Probably related to the throttle hesitation some people have also experienced. Maybe switching rev matching on/off resets it in some way for a while. Who knows?

When I first had the CDV removed I also thought it was better but after a while felt it was pretty much the same. I think the bottom line is that it's just a very ordinary manual transmission implementation.. or maybe in some cases, just Friday built. ?‍

My gearbox shifts just fine. If I was going to be nitpicky it is occasionally a bit balky upshifting into 4th gear but thats usually just short shifting and me being a bit lax.
The rev match and CDV have nothing to do with shift action. As long as the the clutch fully releases correctly then the shift action and syncro performance is totally independent of everything else. The rest is psychosomatic. With some transmissions you can "beat the syncro" on the first to second shift when you are really hammering the trans such as flat foot shifting etc but thats the nature of some gearboxes and their syncro performance in first and second gear, the gears where the syncros work the hardest. Although I'm loath to say ( because I don't believe specific oils have a massive influence on shift performance) if I was you and that bothered by it I'd try changing the transmission fluid to something a fraction lighter than the 75W-80 I think the Supra uses. (my post goblin will be along directly to verify I'm sure, lol) Penrite makes a 70W-75 GL-4. Might be worth a try and see how it feels. It can't hurt anything and might be interesting to see.

Phil

 

[BMWAF]

My gearbox shifts just fine. If I was going to be nitpicky it is occasionally a bit balky upshifting into 4th gear but thats usually just short shifting and me being a bit lax.
The rev match and CDV have nothing to do with shift action. As long as the the clutch fully releases correctly then the shift action and syncro performance is totally independent of everything else. The rest is psychosomatic. With some transmissions you can "beat the syncro" on the first to second shift when you are really hammering the trans such as flat foot shifting etc but thats the nature of some gearboxes and their syncro performance in first and second gear, the gears where the syncros work the hardest. Although I'm loath to say ( because I don't believe specific oils have a massive influence on shift performance) if I was you and that bothered by it I'd try changing the transmission fluid to something a fraction lighter than the 75W-80 I think the Supra uses. (my post goblin will be along directly to verify I'm sure, lol) Penrite makes a 70W-75 GL-4. Might be worth a try and see how it feels. It can't hurt anything and might be interesting to see.

Phil

Clearly you don't have the same issue - my fourth gear engagement is fine, for example. And I'm not being nitpicky: The shift in my Supra is just plain bad some of the time. It's not necessarily the mechanical gear action, it is the entire shift that is borked - right through to how the power is transferred to the clutch. The best way I can describe it is that it feels like a combination of lazy/poor pedal application and timing, but it isn't.. you can do the exact same movements and the result is random: Sometimes the shift is good, othertimes it is dogshit. This randomness applies to all manner of shifting: Lazy shifts; fast shifts, aggressive shifts, etc.

Also for reference, I don't flat shift or treat the car poorly. I am a competent manual driver of over twenty years and am yet to go through a clutch in any car. I'm not usually so confident, but I am 100% sure that in this case, this isn't a skill issue.. before someone chimes in with that nugget.

Now it has been suggested to me that the car rev matches on upshifts as well as downshifts, which if true, would make it a very possible contributor to how our cars shift. ?‍

 

[pk8]

Clearly you don't have the same issue - my fourth gear engagement is fine, for example. And I'm not being nitpicky: The shift in my Supra is just plain bad some of the time. It's not necessarily the mechanical gear action, it is the entire shift that is borked - right through to how the power is transferred to the clutch. The best way I can describe it is that it feels like a combination of lazy/poor pedal application and timing, but it isn't.. you can do the exact same movements and the result is random: Sometimes the shift is good, othertimes it is dogshit. This randomness applies to all manner of shifting: Lazy shifts; fast shifts, aggressive shifts, etc.

Also for reference, I don't flat shift or treat the car poorly. I am a competent manual driver of over twenty years and am yet to go through a clutch in any car. I'm not usually so confident, but I am 100% sure that in this case, this isn't a skill issue.. before someone chimes in with that nugget.

Now it has been suggested to me that the car rev matches on upshifts as well as downshifts, which if true, would make it a very possible contributor to how our cars shift. ?‍

I know the CDV delete is a simple mod but I am wondering if everything was done correctly for your car? Because my car is night and day after the CDV delete, and I have no more issue regardless of the rev match on or off.

 

[pk8]

I know the CDV delete is a simple mod but I am wondering if everything was done correctly for your car? Because my car is night and day after the CDV delete, and I have no more issue regardless of the rev match on or off.

Did you take the rubber spacer and the CDV out?

 

[swrdply400mrelay]

Clearly you don't have the same issue - my fourth gear engagement is fine, for example. And I'm not being nitpicky: The shift in my Supra is just plain bad some of the time. It's not necessarily the mechanical gear action, it is the entire shift that is borked - right through to how the power is transferred to the clutch. The best way I can describe it is that it feels like a combination of lazy/poor pedal application and timing, but it isn't.. you can do the exact same movements and the result is random: Sometimes the shift is good, othertimes it is dogshit. This randomness applies to all manner of shifting: Lazy shifts; fast shifts, aggressive shifts, etc.

Also for reference, I don't flat shift or treat the car poorly. I am a competent manual driver of over twenty years and am yet to go through a clutch in any car. I'm not usually so confident, but I am 100% sure that in this case, this isn't a skill issue.. before someone chimes in with that nugget.

Now it has been suggested to me that the car rev matches on upshifts as well as downshifts, which if true, would make it a very possible contributor to how our cars shift. ?‍

I have noticed an improvement after the CDV delete, but still notice a characteristic similar to with a CDV, but not as pronounced. If that makes sense.

1-2 shift is sometimes still choppy, but for me I think it’s because the clutch has a longer take up than any other clutch I’ve driven. When I left off the clutch, it catches half way coming up, and doesn’t finish grabbing until the pedal is all the way up.

So in essence it still feels like it’s slipping the clutch.

 

[Strat-Supra]

I have noticed an improvement after the CDV delete, but still notice a characteristic similar to with a CDV, but not as pronounced. If that makes sense.

1-2 shift is sometimes still choppy, but for me I think it’s because the clutch has a longer take up than any other clutch I’ve driven. When I left off the clutch, it catches half way coming up, and doesn’t finish grabbing until the pedal is all the way up.

So in essence it still feels like it’s slipping the clutch.

Did the CDV delete months ago and the difference is very noticeable, not sure how one could say it's not. Your point/experience with clutch engagement in this car is spot on. The clutch pedal throw is too long, the pedal sits too high.

I believe this is why the engagement point is so high on the take, with full engagement right before the pedals resting position. This creates a hesitation between shifts that you can feel. Your foot is pushing on the accelerator, the clutch should've fully engaged due to feeling the take in the clutch pedal but the car doesn't take off. Once your foot is completely off the clutch pedal the car takes off.

 

[tracer bullet]

The clutch pedal throw is too long, the pedal sits too high.

Agreed to both! There's this: https://ind-distribution.com/collec...ing-g8x-m2-m3-m4-short-throw-clutch-pedal-arm

But I don't know if it works on our cars (Z4 or Supra). I've been matching the M3/M4 forum but no one has said they've installed it yet. IND's inventory goes down then back up so it would seem someone is buying them. Emails to Rogue basically end up with them not knowing if it works for us yet. I might consider gambling with it one day but would have to have an agreement with them that they'd give a refund if it didn't fit. It might come down to taking the pedal out of our cars and lining them up side by side, and then installing if it looks good. I've seen one Supra pedal assembly (brake and clutch combo) for sale but at $600 I passed. Could then check fitment without even touching the car. Just kind of hoping someone else will try it out first!

So in essence it still feels like it’s slipping the clutch.

What you're saying does make sense, but I'm still surprised. I've found the opposite, after removing it, for me if it's jerky it's me being lazy and not paying attention. It was asked earlier for someone else, but you did get the whole gizmo out, right? The rubber piece and the metal collar over it both? I thought I had a picture of it on my phone but can't find it.

 

[Strat-Supra]

yes, when it happens it's because of me, otherwise it's much smoother. I replaced the whole cylinder, no real reason, just preference.

That will work on the Supra, I spoke with Rogue Engineering about it. I would already have one but I replaced the bushings/pins already with Rogue Engineering's kit. Was told they need to pull one of the bundles from the next shipment, would be a few weeks. Been a few weeks and have not heard from them, emailed Thursday, haven't received a reply yet. I might buy the bundle and try to sell the bushings/pins.

 

[BMWAF]

I went for a long drive today and I can 100% say that the rev matching is complicit in my 1-2 shift problem. With rev matching off for the majority of the drive, I had zero dodgy shifts. As soon as I turned rev matching back on, the hesitation and poor shifts returned at random as per usual. My CDV has been deleted but my gut feeling is that it has no real bearing on the issue, at least in my car.

 

[Keemaca]

Agreed to both! There's this: https://ind-distribution.com/collec...ing-g8x-m2-m3-m4-short-throw-clutch-pedal-arm

@Strat-Supra
This topic needs its own thread, I need this.
How difficult is the installation? Must be a tight fit to get in there.

 

[tracer bullet]

@Strat-Supra
This topic needs its own thread, I need this.

https://www.supramkv.com/threads/rogue-engineering-g8x-m2-m3-m4-short-travel-clutch-arm.26697/

 

[L3roseph]

Just attempted the CVD delete this afternoon. Everything seemed to be going ok but the Motive 0100 wouldn't keep its pressure before I attempted to bleed. Spent hours trying to figure out where the leak was coming from and second guessing myself putting the rubber spacer that was removed with the CDV back in and out on the master clutch cylinder and messing with the slave clutch cylinder for hours until I realized (I think) the problem was with the Motive power bleeder...

I tried covering the hole at the end of the Motive 0100 cap with my thumb and create an air tight seal and the pressure is still not holding. The plastic at the cannister valve seems to be oddly shaped (as seen in the pic below). If this was the problem (not sure if it is), I find this incredibly annoying as the whole purpose of this product is to detect leaks. I have a new replacement Motive 0100 power pressure and another bottle of DOT4 brake fluid inbound while my clutch pedal is on floor because I leaked so much fluid trying figure out where the leak is coming from.

Ironically, the day you posted this comment was the day I was finally able to bleed my clutch after removing the CDV. I also had issues trying to use a Motive power bleeder. Initially, mine was leaking out of the box from multiple places. I tightened all the joints and all seemed well. I was bleeding the clutch line and was almost done, then out of nowhere I got a huge surge of air and fluid out. Perhaps I opened the bleeder too far? But regardless, after that no matter how much I continued bleeding with the power bleeder, all I was getting was straight air with very little fluid. The level never dropped below max.

After pumping up the bleeder and pumping it up over 15 times, I gave up on the power bleeder. At this point, the clutch pedal was stuck to the floor and the cylinder was full of air. I tried the pedal pump/hold method to no avail and also tried a vacuum pump on the bleeder. The only method that finally worked was to reverse bleed the system. I purchased a reverse bleeding kit from Amazon that is basically just a syringe and tube. Here's the link.
Amazon.com: Lwuey Brake Bleed Kit, Hydraulic Disc Clutches Bleeding Kit 100ML Syringe 50cm Hose Oil Fluid Extractor Bleeder Tool Universal for Motorcycle Motorbikes Scooters Quads Brake System Repair Maintenance : Automotive

This worked amazing although is a two person job. I had my wife standing near the reservoir watching for bubbles and to let me know when the reservoir was about to overflow. I pushed a ton of fluid into the system before the level in the reservoir even started to move, indicating the system was full of air. I probably did 4-5 syringes before the level started rising at the same rate as I was pushing fluid into the system. The clutch pedal finally went back to normal and I was ecstatic.

 

[pk8]

Ironically, the day you posted this comment was the day I was finally able to bleed my clutch after removing the CDV. I also had issues trying to use a Motive power bleeder. Initially, mine was leaking out of the box from multiple places. I tightened all the joints and all seemed well. I was bleeding the clutch line and was almost done, then out of nowhere I got a huge surge of air and fluid out. Perhaps I opened the bleeder too far? But regardless, after that no matter how much I continued bleeding with the power bleeder, all I was getting was straight air with very little fluid. The level never dropped below max.

After pumping up the bleeder and pumping it up over 15 times, I gave up on the power bleeder. At this point, the clutch pedal was stuck to the floor and the cylinder was full of air. I tried the pedal pump/hold method to no avail and also tried a vacuum pump on the bleeder. The only method that finally worked was to reverse bleed the system. I purchased a reverse bleeding kit from Amazon that is basically just a syringe and tube. Here's the link.
Amazon.com: Lwuey Brake Bleed Kit, Hydraulic Disc Clutches Bleeding Kit 100ML Syringe 50cm Hose Oil Fluid Extractor Bleeder Tool Universal for Motorcycle Motorbikes Scooters Quads Brake System Repair Maintenance : Automotive

This worked amazing although is a two person job. I had my wife standing near the reservoir watching for bubbles and to let me know when the reservoir was about to overflow. I pushed a ton of fluid into the system before the level in the reservoir even started to move, indicating the system was full of air. I probably did 4-5 syringes before the level started rising at the same rate as I was pushing fluid into the system. The clutch pedal finally went back to normal and I was ecstatic.

glad everything worked out for you. I wonder if you ran out of motor fluid in the bleeder reservoir.

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