CDV?

M

martinb1966

Member
Does it really make fast take offs not so jerky and also where can you get it done in the uk ? preferably if anyone knows anywhere in the herts/beds/cambs area thanks guys
 
it helps with fast take offs certainly...but doesn't do any good whatsoever when you have to granny shift...it just hates to be driven easy.
 
It helps, but then if you drive 20K miles on the original - you'll find you get used to it - I had it done because I can change gear properly and I dont want the clutch slipping 'on purpose' when im giving it beans :driving:

You can buy a modified one from http://www.zeckhausen.com/ which will replace the stock one, look like its still fitted, but give the benefits (It is hollowed so it has less drag on the fluid = no delayed engagement). OR you can do away all together (so long as the pipe can be joined, connected to the clutch / master cylinder / whatever)

Some people have done it themselve, I think Sittingbull posted instuctions on how to , but any decent garage / independant who you trust with hydraulic lines should be able to do this for you, no longer than 1 hour :thumbsup:
 
Yes we can, I meant post a response up without slating the person before and all is well :)
 
SittingBull said:
Try this link:

http://www.bimmerfest.com/forums/showthread.php?t=55083 :thumbsup:

1. Remove NSF wheel.
2. Remove rear aluminium undertray.
3. Use Mole Grips to completely clamp the black flexible hose entering the clutch slave cylinder.
4. Use 2 spanners (13mm & either 15 or 17mm if I remember correctly) to disconnect the flexible hose from the CDV.
5. Unscrew the CDV from the clutch slave cylinder then either replace it with a modified one or do away with it completely (as I did) & screw the flexible hose directly into the slave cylinder.
6. Remove Mole Grips & top-up the brake/clutch reservoir if necessary.
7. Before you re-fit the undertray & wheel, carefully try the clutch pedal. If it seems to be normal (ie NOT "floppy") then you should not have to bleed air from the slave cylinder!

45 minutes tops - unless you encounter problems removing seized undertray bolts (unlikely on a BMW).

If you are insistant on replacing the CDV with a modified version (Warranty fears perhaps?), rather than spend £30-£40 on the US valve you can modify the one you took out..... The CDV has a small "restrictor" insert pressed into it which simply needs removing. Put the CDV in a bench vice & use a hammer & 3mm Allen key to drive it out - easier said than done...

Simples :)
Click to expand...

Need to make sure you put the insert back though otherwise brake/clutch fluid will be everywhere.
 
Before you jump down my throat I suggest you read what I said properly

http://www.z4-forum.com/forum/viewtopic.php?f=25&t=1227&hilit=how+modify+cdv#p17422
 
Removing the CDV or replacing it with a modified one does not cure the kangarooing problem though. It merely allows more instantaneous engagement of the clutch. The kangarooing is a fuelling issue and is a characteristic of these engines which cannot be removed, You just learn to drive around the issue as you get more used to the car. The issue also eases as the miles build up on the engine in my experience.

This comes from a not so young man with substantially less money than sense. Stop trolling, it's becoming a PITA.
 
dgm said:
Removing the CDV or replacing it with a modified one does not cure the kangarooing problem though. It merely allows more instantaneous engagement of the clutch. The kangarooing is a fuelling issue and is a characteristic of these engines which cannot be removed, You just learn to drive around the issue as you get more used to the car. The issue also eases as the miles build up on the engine in my experience.

This comes from a not so young man with substantially less money than sense. Stop trolling, it's becoming a PITA.
Click to expand...

I don't get this, because my car doesn't kangaroo accelerating in 2nd from about the speed I'd normally enter that gear at had I come from 1st.

Logically, to me, it is associated with coming onto the power from 1st to 2nd, and the request for throttle and clutch not matching, and so a cycle of adjustment/jerk and through a sensitive throttle, more jerk being generated.

Of course, any car will kangaroo, even ones without a CDV, but it is, imho, the non-linear or intuitive action of the CDV that helps set it going all that much easier.

Dave
 
Mr Whippy said:
Logically, to me, it is associated with coming onto the power from 1st to 2nd, and the request for throttle and clutch not matching, and so a cycle of adjustment/jerk and through a sensitive throttle, more jerk being generated.
Click to expand...

That is exactly what happens, you can't match the throttle and clutch properly when changing gear because the biting point of the clutch effectively moves depending on how quick you release the clutch. You only realise how vague the biting point is when you remove the CDV.
 
Despite what the troll says in his usual abusive manner without explanation as to why he's correct, the CDV removal/alteration doesn't cure the kangarooing. Nor is he an expert on the subject of the CDV, he has merely copied and pasted information that has been available on the internet for many years. Nothing wrong with that in itself until you use it to try and pass yourself off as an expert.

It is a worthwhile modification though as the delay caused in delivering the power when the OEM CDV is in place is infuriating. This isn't a new discussion remember, this is an issue which has been in existence since the inception of the E46 M3 in 2001.
 
wow what did i start there ! :D so to sum up its defo worth doing but bmw dont like it ! so best to wait till warranty runs out im thinking ! thanks for all the views and interesting reading maybe i should be careful what i ask in future wouldnt want to cause an all out riot ! :evil: :fuelfire: ha ha ha ha seriously though gents/ladies thanks for all the good advice/input
 
Top pup said:
Mr Whippy said:
Logically, to me, it is associated with coming onto the power from 1st to 2nd, and the request for throttle and clutch not matching, and so a cycle of adjustment/jerk and through a sensitive throttle, more jerk being generated.
Click to expand...

That is exactly what happens, you can't match the throttle and clutch properly when changing gear because the biting point of the clutch effectively moves depending on how quick you release the clutch. You only realise how vague the biting point is when you remove the CDV.
Click to expand...

The CDV mod definitely gives you far more control over the clutch and I think this allows you to control the kangarooing when it starts or when you anticipate that it's about to start. As you become more aware of how to control the problem it becomes second nature to react to it and only very occasionally are you caught out. The severity of it also seems to vary between engines, my M3 with an unmodified CDV very rarely displayed the issue whilst it is much more prominent in my Z4 with the modified valve fitted. I know of hugely varying experiences between M3 owners of the extent of this special BMW feature .

For me the brand of fuel also has an effect. My own car is much less prone to kangarooing when using Tesco 99 as opposed to Vpower.
 
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