CDV Delete

J

Jasper ham

Member
Guys - wanting to delete the Clutch Delay Valve on my 3.0 SE E85, been quoted £45 + vat to do the job. Firstly, will I notice a big difference? Getting frustrated with jumpy changes between 1st and 2nd? And secondly is this a reasonable cost to complete the job?
Cheers
 
Yes you will notice a huge difference. I got mine done for a drink. I takes a few minutes on a ramp so £54 sounds a bit steep.
 
Agree that it's worth it. You learn to compensate, but then you drive another car without such an aggressive CDV (or none) and wonder why you bother!

Mine was cheaper than that, but not by much (about £35 + VAT, IIRC). It's probably a 15-20 minute job to remove, if they are thorough, and maybe double that if you want them to mod the valve and re-fit it.
 
Its a pretty straight forward job well within the DIY capability.

http://z4-forum.com/forum/viewtopic.php?f=25&t=1227
 
Toe-side said:
Its a pretty straight forward job well within the DIY capability.

http://z4-forum.com/forum/viewtopic.php?f=25&t=1227
Click to expand...

...if you have a drive/garage, axle stands, the required spanners, a jack, can do a solo re-bleed and aren't fussed about the peace of mind of getting it done at a trusted local garage. Agree that it is worth doing it yourself otherwise! :)
 
MrPT said:
Toe-side said:
Its a pretty straight forward job well within the DIY capability.

http://z4-forum.com/forum/viewtopic.php?f=25&t=1227
Click to expand...

...if you have a drive/garage, axle stands, the required spanners, a jack, can do a solo re-bleed and aren't fussed about the peace of mind of getting it done at a trusted local garage. Agree that it is worth doing it yourself otherwise! :)
Click to expand...

Point taken :wink: :)
 
Mine was done for free :P however it does not feel as good as i expected as it is still a bit jerky getting away and shifting 1-2 especially when cold.
 
Right, book it in tomorrow. I did a very scientific experiment, I went to the B&Q car park, turned the dtc off and tried a bit of drifting, mint. But it was damp and I did have my timing pulley replaced and my timing done today. You don't get that embarrassing gear change malarkey that makes you look a chump at lights, it's a massive improvement. I also stuck a bottle of red ex alternative in last week, that was a small improvement(yeah fifth gear,lol). Book it in, you won't regret it.
 
This...

2alpsade said:
Engineering and dynamics (vibration) background here, and a full-on understanding of this system as its been in use for donkeys years and is known for problems, so bear with this short explanation...and I know there has been plenty of uneducated rambling on this elsewhere, but that is a problem with forums and incorrect info, sadly :|

The CDV is only in the system to prevent lash into the DMF if the clutch is released rapidly and/or without control. The CDV slows the fluid flow on clutch release via its restricting orifice, hence automatically reduces the lash in the system, gives a 100% repeatable clutch release rate and prevents accidental (or careless) damage to the DMF. Removing a CDV valve whilst being the 'manly' thing to do, is in effect putting your DMF at risk if you make an error with your clutch control. It has NO effect on clutch judder per se, only its apparent severity. Clutch judder is a result of a high and hot spots due to non-flatness and localised heating on the clutch plates. The hot spot comes from local heating friction during clutch engagement, and may be (for example instance) a slight inbuilt and within tolerance misalignment between plates on take-up (there is after all, a 360degree arc of take-up, so a potential 1 in 360 chance of matching high and hot spots at instant of drive take-up). The high and hot spot interaction results in a grab-release-grab-release of the DMF drive and friction plates, and this causes the DMF drive springs to oscillate at their undamped natural frequency (imagine fixing a rope at one end and flicking the other repeatedly and seeing the waves it sets up). That shakes the car to buggery as the drive is taken up and released in pulses..... The undamped oscillation then causes the springs to clatter their guides and housing and reduces the lifespan of the springs, and can crack the casing and/or flywheel itself...which is a right-off of the DMF. If you remove the CDV on a DMF with a minor issue, you may improve the engagement slightly as the plates will come together faster, and any fluctuations pass more quickly (basic dynamics) but still exist. That is masking, not fixing the fault.

Friend of mine works as a main dealer service manager. He's lost count of the number of DMF's that they get in with 'slight judders' and on opening the joint, bits of DMF fall out of the bell housing. I recently had in my hands a 9k-miles old DMF which had been run without a CDV. It was trashed. £1200 again please, sir, for the benefit of giving you back your drive. Leave the CDV in: BMW put it there for a bloody good reason. If the clutch judders, it has a DMF problem. Full stop.

From a personal POV, I would never buy any used car from any manufacturer where I thought the CDV may have been removed by a previous owner unless the DMF had been exchanged just prior to my purchase.
Click to expand...

But as in all things, your car your choice.
 
That sounds a bit worrying Stuart? Don't want to have reliability issues with the clutch. Looking at some previous threads though a lot of people have done it, no one has said they have had ny issues with the DMF since ........hmmm need to think about it more :cry:
 
I read about the CDV last month and spoke to BMW specialist about it and he said he wouldn't recommend it at all and gave reasons as per the post by Stuart.
I haven't had it done.
 
Is it possible to put some kind of poll chart up that shows who's had it carried out and what people have had problems due to the cdv

Basically want to see the relationship with how many have done it and the percentage of problems
 
Stuart Truman said:
This...

2alpsade said:
Engineering and dynamics (vibration) background here, and a full-on understanding of this system as its been in use for donkeys years and is known for problems, so bear with this short explanation...and I know there has been plenty of uneducated rambling on this elsewhere, but that is a problem with forums and incorrect info, sadly :|

The CDV is only in the system to prevent lash into the DMF if the clutch is released rapidly and/or without control. The CDV slows the fluid flow on clutch release via its restricting orifice, hence automatically reduces the lash in the system, gives a 100% repeatable clutch release rate and prevents accidental (or careless) damage to the DMF. Removing a CDV valve whilst being the 'manly' thing to do, is in effect putting your DMF at risk if you make an error with your clutch control. It has NO effect on clutch judder per se, only its apparent severity. Clutch judder is a result of a high and hot spots due to non-flatness and localised heating on the clutch plates. The hot spot comes from local heating friction during clutch engagement, and may be (for example instance) a slight inbuilt and within tolerance misalignment between plates on take-up (there is after all, a 360degree arc of take-up, so a potential 1 in 360 chance of matching high and hot spots at instant of drive take-up). The high and hot spot interaction results in a grab-release-grab-release of the DMF drive and friction plates, and this causes the DMF drive springs to oscillate at their undamped natural frequency (imagine fixing a rope at one end and flicking the other repeatedly and seeing the waves it sets up). That shakes the car to buggery as the drive is taken up and released in pulses..... The undamped oscillation then causes the springs to clatter their guides and housing and reduces the lifespan of the springs, and can crack the casing and/or flywheel itself...which is a right-off of the DMF. If you remove the CDV on a DMF with a minor issue, you may improve the engagement slightly as the plates will come together faster, and any fluctuations pass more quickly (basic dynamics) but still exist. That is masking, not fixing the fault.

Friend of mine works as a main dealer service manager. He's lost count of the number of DMF's that they get in with 'slight judders' and on opening the joint, bits of DMF fall out of the bell housing. I recently had in my hands a 9k-miles old DMF which had been run without a CDV. It was trashed. £1200 again please, sir, for the benefit of giving you back your drive. Leave the CDV in: BMW put it there for a bloody good reason. If the clutch judders, it has a DMF problem. Full stop.

From a personal POV, I would never buy any used car from any manufacturer where I thought the CDV may have been removed by a previous owner unless the DMF had been exchanged just prior to my purchase.
Click to expand...

But as in all things, your car your choice.
Click to expand...

Hmmm im not to sure I agree with your quote

There are plenty of other marques of cars that have DMF's and no cdv and no problems

The cdv prevents drive train shock from rapid clutch realease, in other words if you too stupid to drive a manual and just dump the clutch every time it smooths out the clutch realease

For 99% of people who can drive properly how is there going to be any damage to the clutch or DMF?

Also with the cdv in place, the clutch release is the same speed every time, which is fine for everyday pulling away, buy say you want to lunch away from the lights you would release the clutch faster so you release the peddle faster but the cdv prevents this as it release the clutch at the same speed everytime

Which cause more clutch wear

So why would anybody want one on a sports car?

As for a dealer anything that goes wrong with a clutch that has had the cdv removed, the dealer is obviously going to say thats why

But thats just my opinion, I have had the cdv out of my z4 for the last year and on my e46 for two years with no problems and wouldnt hesitate to have it out of the next bmw I have

And for what its worth, £40 sounds ok if you don't have the equipment to remove it yourself or can be bothered to get fluid all over you lol



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hundreds 0f posts on here over the years on removal of cdv with great improvement reported, never seen a posr yet re dmf probs until stuarts one . i would want to see a lot more opinions i think to get a balanced view, a lot of vehicles especially fords have dmf problems, rattles, breakages etc and dont have cdv 's fitted in the sytem. z4's are well known to have rattly clutch springs if you switch off without your foot on the clutch, all quite normal according to the dealers and nothing to worry about. when someone starts quoting technical jargon it can become gospel and itself become part of the misinformation around on forums, as we know from vanos on the s50 engine, the rod bearings on the s54, and the rear diff mount on the z3's, it became a case of when , not if, they would fail when it was only ever a percentage of affected vehicles. not wishing to cast aspertions on anyones knowledge but using dynamics whether fluid or thermo nuclear to over technically sex up (sorry but very wary after blair and campbell's dodgy dossier on wmd ) a possibly non existant , or little known problem is possibly a bit premature. I wonder how many people on here are re ordering cdv's from the dealers already. when stuart first got immie he mentioned that he wasnt going to change the cdv as he just got used to it but didnt mention the dmf at all then, just wonder where this story came from. ....ok getting my tin hat on ready for some flak !!! remember not doubting anyones knowledge but its an emotive issue and need a wider view. :thumbsup:
 
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