Manual Transmission - CDV Question

[m3elmo]

Originally Posted by Djdnav

https://www.ebay.com/itm/F80-F82-E9X...0AAOxyrUtQ1H35

This also improved the feel of mine

yes I've recently done this mod and it helps the bottom feel of the clutch now I need to improve the top of the movement. reading this and other threads it makes sense it's the cdv.

[YRAGAEL]

I finally got my E90 slave cylinder installed and clutch feel is miles better now. Another thing that helps is the BMS clutch stop - takes up some of the excess pedal travel before the clutch engages.

[jpy1980]

Originally Posted by YRAGAEL

I finally got my E90 slave cylinder installed and clutch feel is miles better now. Another thing that helps is the BMS clutch stop - takes up some of the excess pedal travel before the clutch engages.

Please explain exactly what you did as I'm interested. Does the e90 SC not have a CDV?

[DLag30]

Originally Posted by jpy1980

Please explain exactly what you did as I'm interested. Does the e90 SC not have a CDV?

the e90 slave cyl do not have a the little orifice. I bought one and installed it on my car. I later fiddled with the original one found it pretty easy to remove the orifice.

[jpy1980]

Originally Posted by DLag30

the e90 slave cyl do not have a the little orifice. I bought one and installed it on my car. I later fiddled with the original one found it pretty easy to remove the orifice.

Nice what was the difference in feel?

Was there a marked improvement?

[YRAGAEL]

Once you remove the restriction (CDV), the movement of the pressure plate is consistent with the movement of the clutch pedal - there is now nothing slowing down the flow of hydraulic fluid so modulating the clutch off the line is much easier.

E90's have the CDV as a valve separate from the slave cylinder, so it's easy to swap out. For F-Series manual transmissions, the CDV is incorporated into the slave cylinder. To remove it you have two options: open up the slave cylinder and manually remove the restrictor piece, or buy and install an E90 slave cylinder - it's exactly the same as F-Series slave, but it doesn't have the CDV restriction.

I'd be curious to know why BMW feels the CDV is such an essential part of their manual trans cars - even their M-cars, as it seriously degrades the operation of the clutch. Are we doing some harm to the drivetrain by removing the CDV? I had a diff bearing race fail in my previous manual 335i and had to replace my diff. Maybe that was that CDV removal related?

[jpy1980]

Originally Posted by YRAGAEL

Once you remove the restriction (CDV), the movement of the pressure plate is consistent with the movement of the clutch pedal - there is now nothing slowing down the flow of hydraulic fluid so modulating the clutch off the line is much easier.

E90's have the CDV as a valve separate from the slave cylinder, so it's easy to swap out. For F-Series manual transmissions, the CDV is incorporated into the slave cylinder. To remove it you have two options: open up the slave cylinder and manually remove the restrictor piece, or buy and install an E90 slave cylinder - it's exactly the same as F-Series slave, but it doesn't have the CDV restriction.

I'd be curious to know why BMW feels the CDV is such an essential part of their manual trans cars - even their M-cars, as it seriously degrades the operation of the clutch. Are we doing some harm to the drivetrain by removing the CDV? I had a diff bearing race fail in my previous manual 335i and had to replace my diff. Maybe that was that CDV removal related?

Do you have the part number for the e90 slave ?

[Kilabyte]

Originally Posted by YRAGAEL

Once you remove the restriction (CDV), the movement of the pressure plate is consistent with the movement of the clutch pedal - there is now nothing slowing down the flow of hydraulic fluid so modulating the clutch off the line is much easier.

E90's have the CDV as a valve separate from the slave cylinder, so it's easy to swap out. For F-Series manual transmissions, the CDV is incorporated into the slave cylinder. To remove it you have two options: open up the slave cylinder and manually remove the restrictor piece, or buy and install an E90 slave cylinder - it's exactly the same as F-Series slave, but it doesn't have the CDV restriction.

I'd be curious to know why BMW feels the CDV is such an essential part of their manual trans cars - even their M-cars, as it seriously degrades the operation of the clutch. Are we doing some harm to the drivetrain by removing the CDV? I had a diff bearing race fail in my previous manual 335i and had to replace my diff. Maybe that was that CDV removal related?

I feel if anything a CDV shortens the life of a clutch.

[YRAGAEL]

>> I feel if anything a CDV shortens the life of a clutch <<

In my experience I would say no. I put a new clutch in an E36 M3 at 100k miles with CDV valve removed and sold the car at 235k miles with the same clutch in it working fine. Same story with my previous N54 335i - removed CDV at about 75k miles and sold the car at 150k miles with original clutch still in it. YMMV, of course.

>> Do you have the part number for the e90 slave ? <<

21526785964

[Kilabyte]

^ I meant having one. It adds unnecessary slip when releasing the pedal fast. I've taken it out in my previous cars but not in the f80 just yet.

[RElias21]

Is this an easy job for a DIY, or should you have a shop do it?

[GTABurnout]

Interested in a DYI if there is one around.

[Morgen Black]

I just finished removing the CDV in my 6MT F80 and it feels glorious. I remember removing the in-line CDV on my E46 M3 a few weeks after delivery and it is one of the best mods you can do to improve the driving feel.

I put the F80 on the Quickjack and removed the little bugger in under 35 minutes. Hooked up the pressure bleeder and finished bleeding the clutch in under 45 minutes. Counting prep and clean up, I was done in under 2.5 hours.

MB