Group Buy CDV

The CDV was designed for driver comfort so that no matter how hopeless you are with a manual gearbox you can still have a reasonably smooth gearchange. The clutch as you said is the part that suffers most. When I first got the 330 and tried to launch it from the traffic lights the revs just went though the roof as the clutch slipped. To me that was scary rather than usefull.
You should try telling the dealer that your worn out clutch is a direct result of the CDV when the time comes. I don't think he or she would be able to argue the point much!
I've seen plenty of standard and modified CDV's and the only difference I've seen is the bore inside. There is no mechanism or parts. The way it works is to slow up the release bearing return by forcing the fluid through a restricted opening so that no matter how fiercly you drop the clutch, the mechanism will engage in its own sweet time once it gets the fluid back through the tiny restrictor.
If you don't want metal shavings in the system then clean them out before you fit it. Blow through it with an airline or something.
As for drivetrain wear have you ever driven a CSL etc with the adjustable gear change button? If you set that to maximum the gearchange is brutal. Even on the CSL racecars at Simpsons the settings are always left somewhere around midway. There's no way BMW were worried about drivetrain wear when they fitted that option and bear in mind the SMG is just a manual gearbox with actuators. To date there's never been a single drivetrain failure on the racecars other than wheel bearings.
 
I've been umming and arring about doing this but I think i will!

I find whenever I drive my car hard it stinks of clutch when I stop - now I have driven other cars just as hard and never had any clutch problems - the more I read the more I think it is the CDV doing this!

So is the group buy on??
 
It might be expensive shipping but our friends over the pond don't hang about:

EAST MIDLANDS AIRPOR,
GB 21/08/2007 13:43 IN TRANSIT TO
PHILADELPHIA,
PA, US 21/08/2007 8:42 DEPARTURE SCAN
EAST MIDLANDS AIRPOR,
GB 21/08/2007 8:48 REGISTERED WITH CLEARING AGENCY / SHIPMENT SUBMITTED TO CLEARING AGENCY
21/08/2007 8:48 REGISTERED WITH CLEARING AGENCY / RELEASED BY CLR AGENCY. NOW IN-TRANSIT
PHILADELPHIA,
PA, US 21/08/2007 2:31 EXPORT SCAN
21/08/2007 0:46 ARRIVAL SCAN
PARSIPPANY,
NJ, US 20/08/2007 22:25 DEPARTURE SCAN
20/08/2007 19:29 EXPORT SCAN
20/08/2007 19:28 ORIGIN SCAN
US 20/08/2007 19:24 BILLING INFORMATION RECEIVED
 
Curtis said:
The CDV was designed for driver comfort so that no matter how hopeless you are with a manual gearbox you can still have a reasonably smooth gearchange. The clutch as you said is the part that suffers most. When I first got the 330 and tried to launch it from the traffic lights the revs just went though the roof as the clutch slipped. To me that was scary rather than usefull.
You should try telling the dealer that your worn out clutch is a direct result of the CDV when the time comes. I don't think he or she would be able to argue the point much!
I've seen plenty of standard and modified CDV's and the only difference I've seen is the bore inside. There is no mechanism or parts. The way it works is to slow up the release bearing return by forcing the fluid through a restricted opening so that no matter how fiercly you drop the clutch, the mechanism will engage in its own sweet time once it gets the fluid back through the tiny restrictor.
If you don't want metal shavings in the system then clean them out before you fit it. Blow through it with an airline or something.
As for drivetrain wear have you ever driven a CSL etc with the adjustable gear change button? If you set that to maximum the gearchange is brutal. Even on the CSL racecars at Simpsons the settings are always left somewhere around midway. There's no way BMW were worried about drivetrain wear when they fitted that option and bear in mind the SMG is just a manual gearbox with actuators. To date there's never been a single drivetrain failure on the racecars other than wheel bearings.

OK I'm going to take my CDV out and have a look at it myself, there can only be a restricted opening or a one way valve in there, it can't be that hard to modify it.

I have to agree with Curtis on the drivetrain issue, I can think of a lot of situations where there will be more drivetrain shock than a poor gear change without a CDV could ever cause.
 
I'm sure its called a delay VALVE for one reason alone, an that is because it has a valve in it.

If the pipe was just restricted it would also restrict you from putting your foot on the clutch quickly which it does not do, it only affect you when you release the clutch.

I'm in on the group purchase, if anybody else want to come in then let me know.
 
The dictionary defines a valve as any device for halting or controlling the flow of a liquid, gas or any other material through a passage, pipe, inlet, outlet etc. The key word is "controlling"

clutch-lock-valve-3.jpg

This is the same type of valve that was fitted to my car. It doesn't have a valve built into it because it is in itself a valve. No internals, just a restricted internal bore (1.5mm ). The rest of the clutch lines have a 3.5mm bore size. The modified valve on the right has a 3.5mm bore to match the pipework. According to BMW, the reason the clutch can disengage quicker than it engages is because the pressure exerted by pressing the pedal is much greater than the pressure the clutch cover exerts on the return cycle. Makes sense really, if the pedal didn't exert more pressure than the clutch cover you wouldn't be able to disengage the clutch. Yours could be different, time will tell.

I don't think this thread was getting intense! It's a lot more interesting than the usual " what's the best way to pick my nose while shifting from 2nd to 3rd gear " threads! :yawn:
 
I'm just going on what I have read below from http://www.zeckhausen.com/cdv.htm

The Clutch Delay Valve (CDV) is a one-way restrictor installed by the factory between the clutch slave cylinder and clutch master cylinder, as shown in Figure 1. It "delays" the engagement of the clutch, much like old record players used a damped tone-arm to gently lower the needle onto the surface of a record.

The solution is to replace* the CDV with a modified valve which has had the interior parts carefully removed. We do not drill these valves. Drilling will damage the taper at both ends of the valve. The male tapered end seals against the female taper of the clutch slave cylinder. And the male hydraulic fitting seals against the CDV's tapered seat at the female end. It does not seal via the threads. Drilling a CDV may cause it to leak under pressure and leave bits of valve material behind, potentially migrating into and damaging the clutch hydraulics.

We have developed a technique for removing the interior valve and spring without damaging the delicate tapered seat at the female end and without touching the taper on the male end. Zeckhausen Racing provides a free service to modify CDVs which are mailed to us. Click here for details.
 
I don't understand why the non-M have a different valve to the M versions. Surely they are the same size etc and if it is open - should be interchangeable?
 
pvr said:
I don't understand why the non-M have a different valve to the M versions. Surely they are the same size etc and if it is open - should be interchangeable?

Different models will have clutch covers with clamping forces to suit the engine, higher on the M's for the extra torque and lower on the non M's for a lighter pedal.
To get the clutch to disengage at the same rate will require a smaller restriction to compensate stronger springs in the clutch.
 
Which is why on the M I did not notice the valve so much as I did on the 3.0 then.

The M with valve drives the same as my 3.0 without it
 
If you guys don't mind waiting until the weekend I will take my CDV out and get some pics of it. I will have a go at modifying it myself and let you know how I get on.
 
I am more thna happy to wait.

Also I work for a CNC machine shop and if it is something that can be easiyl drilled out, then it maybe worth sourcing from local dealer and miding ourselfs, but I am still under the impression that there is more to it than a pipe restriction.
 
I have an old CDV from my 3.0 (my original one). You can have that to play with. I am in East Sussex as well.
 
Mine came in the post yesterday, being fitted next week. I'll post some pictures tomorrow. It has a 3-4mm hole straight through the middle, I don't know what was in there before, but looks like a very simple bit of metal that cost many $$. I'm sure the standard part couple be modified with vice & drill.
 
OK photo's as promised:

148DSC01484.JPG


148DSC01481.JPG


148DSC01488.JPG


I'll post the pictures of the original once I've swapped them over. :)
 
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