Manual Trans CDV

[HerrK]

Just wondering if anyone has replaced their CDV (Clutch Delay Valve) item 16 in Diagram. The E89 uses the same CDV as the E90 (21526764872). Zeckhausen racing http://zeckhausen.com/cdv.htm#CDV sells a modified unit. Basically they remove the guts (orifice) to allow a more rapid clutch engagement/disengagement. This will probably be a summer mod for me when I've got the car up on the jackstands for its 10K 296 wheel inspection.

[KCZ4]

I did this exact mod on my 2006 M3, I never really could tell the difference, however alot of people swear by it. Some just removed the valve, but I did install the gutted one you described.

[skier219]

Just be careful -- it's usually there to protect the 'glass' parts of the transmission. Even minor accidental missteps of the clutch pedal could make something go bang from a dead stop if the plates hook up to abruptly. Then again, if it improved feel, maybe there would be less of a chance of killing the engine to begin with. There is definitely a lot of molasses in this car's clutch release.

BTW, I believe most valves only affect engagement.

[skier219]

Originally Posted by KCZ4

I did this exact mod on my 2006 M3, I never really could tell the difference, however alot of people swear by it. Some just removed the valve, but I did install the gutted one you described.

It really depends on the time constant of the valve. Most of them add just enough delay to prevent damage from a sidestep. In normal driving, most of us are probably not fast enough to notice unless we're Evil Knievel....

[nicolak]

My opinion is if you have driven manual transmissions for most of your driving history then removing the valve will make a marked improvement. I have been using manual transmissions for more than 20 years. The first BMW I purchased I could not use the clutch smoothly, could not understand why until I read on E90 about the CDV. I purchased a gutted one from a vendor for my 335i, and on the Z4 I just saved a few dollars and drilled it out, not difficult really.

I did the Z4 directly after leaving the dealer, first thing. I really dislike that valve.

[skier219]

Originally Posted by nicolak

My opinion is if you have driven manual transmissions for most of your driving history then removing the valve will make a marked improvement. I have been using manual transmissions for more than 20 years. The first BMW I purchased I could not use the clutch smoothly, could not understand why until I read on E90 about the CDV. I purchased a gutted one from a vendor for my 335i, and on the Z4 I just saved a few dollars and drilled it out, not difficult really.

I did the Z4 directly after leaving the dealer, first thing. I really dislike that valve.

So how easy is this mod? Do you have to bleed and refill the clutch hydraulics? Is it simply a restriction, or is there a check, BB, or some other directional control in there? I am curious, since the Z4 clutch is fussy from a stop sometimes, compared to other cars I have owned.

[HerrK]

Originally Posted by skier219

So how easy is this mod? Do you have to bleed and refill the clutch hydraulics? Is it simply a restriction, or is there a check, BB, or some other directional control in there? I am curious, since the Z4 clutch is fussy from a stop sometimes, compared to other cars I have owned.

You will have to bleed the system after R&R. Not sure what's inside - maybe Nicolak can enlighten us. I was thinking about buying one, as their only like $8-9, just to see what it looks like for a DIY. The most important in DIY will be to get it cleaned out after rework to avoid contaminating the slave unit.