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General E46 Forum
This is the place to get answers, opinions and everything you need related to your E46 (sedan, coupe, convertible and wagon) BMW!

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Old 11-09-2012, 02:48 PM   #1
sharkey62
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Exclamation What are pros and cons of removing CDV

Hi
I am new to BMW's. I have read a few posts on here when I have been searching for information on clutch delay valves. I have a 2001 320i and cannot get a smooth gear change. I have been driving for 30 years so feel like a learner when the car jerks on gear changes. I have read that most people have removed the valve but just wondered if there were any negatives by doing this. Would it solve one problem and create another.
Any info would be most appreciated.
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Old 11-09-2012, 03:09 PM   #2
empirem3
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Well the downside is that you can smoke your fly wheel/clutch in no time if you have a few bad shifts.

but the problem may be else where
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Last edited by empirem3; 11-09-2012 at 03:12 PM.
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Old 11-09-2012, 03:09 PM   #3
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Don't think it would solve your problem. The delay valve limits how fast the clutch will engage, which some people don't like. So out it goes.

Any idea what oil is in the transmission? Some people use thinner oil in cooler climates, such as RedLine D4 ATF. Apparently it shifts smoother when it's cold.

Your throwout bearing (translation: thrust bearing) might be on its way out. How many miles on the clutch?
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Old 11-09-2012, 03:27 PM   #4
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CDV delete and add a clutch stop from somewhere like UUC or Rogue. simple and easy mods that improve shift feel noticeably. that said, it still will not be as easy to drive smoothly as, say, a Honda manual gearbox. the E46 has a dual mass flywheel and self-adjusting clutch which can make smooth shifts somewhat tricky.
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Old 11-09-2012, 03:49 PM   #5
hamadyr
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First, the CDV: The Clutch Delay Valve is intended to slow down clutch engagement in order to minimize powertrain stress. Think of it as a damper between the clutch cylinder and clutch mechanism. It is also an engineer's approach to preventing burnouts. If you try really hard, you will burn the clutch before the tires :-)

The clutch on an E46 BMW is a complex affair:
- Dual mass flywheel. (Two separate pieces assembled with springs to control movement relative to one another.)
- Ridgid hub disk (NO SPRINGS so the simplest piece)
- Self-Adjusting Pressure Plate. (Complex spring mechanism intended to maintain consistent pedal travel regardless of wear levels)
- Hydraulic flow valve (a.k.a. CDV)

If you can't get smooth engagement in normal city driving, you may want to have your mechanic check the car. Often, this behaviour is the result of a broken flywheel.

CDV removal is simple and harmless as long as you don't abuse ...

Last edited by hamadyr; 11-09-2012 at 03:52 PM.
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Old 11-09-2012, 04:02 PM   #6
lcoleman
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I have never verified this, but my opinion is that the "weird" characteristics of the e46 are due to the self-adjusting design. The only way I know to remedy this is here:

http://www.uucmotorwerks.com/flywheel/LFWLE46SH.htm

...and it's quite expensive. I have no personal experience with this, for what it's worth. Maybe something to consider when your clutch wears out. Removing the CDV didn't really help me, personally.
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Old 11-09-2012, 04:04 PM   #7
sharkey62
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Thank you for all of your feedback.
The car has only done 48K and has been serviced by BMW main dealers. I have only had the car since August but have noticed that it does seem a bit sluggish and jerky when pulling away from a standiing start. I previously owned a V6 ford Mondeo that was very quick on gear changes.
I don't really want to burn out the clutch so am thinking after reading the first reply that by taking out the cdv that could cause some expensive problems. I will get the car looked at soon and get the oil changed as suggested and see if that helps. Just hope ther is not a more serious problem lerking.
Thank you again for your assistance being a girlie find it quite confusing sometimes. I didn't realise just how much different a BMW engine is compared to other cars but I do love him.
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Old 11-09-2012, 04:57 PM   #8
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Quote:
Originally Posted by sharkey62 View Post
Thank you for all of your feedback.
The car has only done 48K and has been serviced by BMW main dealers. I have only had the car since August but have noticed that it does seem a bit sluggish and jerky when pulling away from a standiing start. I previously owned a V6 ford Mondeo that was very quick on gear changes.
I don't really want to burn out the clutch so am thinking after reading the first reply that by taking out the cdv that could cause some expensive problems. I will get the car looked at soon and get the oil changed as suggested and see if that helps. Just hope ther is not a more serious problem lerking.
Thank you again for your assistance being a girlie find it quite confusing sometimes. I didn't realise just how much different a BMW engine is compared to other cars but I do love him.
It's a tossup.. what kind of a driver are you? The CDV delete is great for the driving enthusiasts, but I just feel that the daily driver isn't going to feel much of a difference.. I did mine recently but I did it while installing a new clutch and flywheel, which is another story I still need to post about here sometime.

PM me if you end up doing a clutch replacement..
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Old 11-09-2012, 05:45 PM   #9
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I do a mix of urban and extra urban driving on a daily basis. I don't tend to drive too hard but neither am I driving Miss Daisy! I just like like to be able to take off when I want to rather than having the lag. I have read that on changing gear that it is advised to have the RPM at around 3000. Is this the case or will this not make any difference. Sorry if this is a dumb question.
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Old 11-09-2012, 05:48 PM   #10
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I'd guess that 3000 RPM bit is just a guideline for beginners. You're not a beginner, so I'd suggest you just drive it how you want to drive it. You probably don't even watch the tach when you're deciding when to shift - we do it by ear.
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Old 11-09-2012, 05:55 PM   #11
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A relatively aggressive start tends to be smoother, or at least easier to do smoothly, from what I've seen.
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Old 11-09-2012, 06:15 PM   #12
sharkey62
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Thanks everyone. I will get the car checked over for any major faults and start driving him a bit harder!
Thanks Hamadyr for your breakdown re the clutch and the different components as a complete BMW novice found it very useful to know how it was made up.
Was a bit worried coming on here being a female petrol head and not really knowing jack about engines just like driving fast cars but you have been great.
Thanks again
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Old 11-09-2012, 09:55 PM   #13
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Quote:
Originally Posted by sharkey62 View Post
I do a mix of urban and extra urban driving on a daily basis. I don't tend to drive too hard but neither am I driving Miss Daisy! I just like like to be able to take off when I want to rather than having the lag. I have read that on changing gear that it is advised to have the RPM at around 3000. Is this the case or will this not make any difference. Sorry if this is a dumb question.
Someone help this gal with a vanos fix!
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Old 11-10-2012, 07:09 AM   #14
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FWIW, my mechanic--one of the best BMW only shops around NYC---suggested not doing the CDV delete.
The shop does Dinan installs so it's not that he's unconcerned about performance. I assume he knows more than me about such things, so I just forgot about it.
I did install a clutch stop which made a small difference, but honestly, the key to smooth shifts is good technique.

Last edited by avincent52; 11-10-2012 at 09:00 AM.
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Old 11-10-2012, 07:17 AM   #15
sharkey62
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Thanks for your info. I will work on technique and see if it improves.
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Old 11-10-2012, 07:51 AM   #16
WDE46
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A CDV delete isn't going to hurt, but most of the time you're not shifting fast enough for it to really slow you down.
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Old 11-11-2012, 04:40 PM   #17
alkemyst
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My biggest con was I was getting where I 'shifted' but was like hitting the gate and wouldn't go into gear. Especially my 2-3rd gear shift at times. I shift very fast.

Once I removed the CDV (and I resisted for 15,000 mile), that problem was gone.

Last edited by alkemyst; 11-11-2012 at 04:40 PM.
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Old 11-11-2012, 05:18 PM   #18
Airborne82id
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Each car shift differently; The same with drivers ...

I just read the 3000rpm comment; it's not really a rule but it does- as someone else noted- help a beginner with a reference point where to shift.

Generally, it's a lot easier to shift smoother @ higher rpm than lower. Once i'm in gear I like to maintain it @ 2000 rpm. I have friends where they stay in 3rd at 40- 45mph @ 3k+ rpm; Where I would drop it to 4th @ slightly above 2000 rpm

Basically I shift around 4k+ rpm and stay in gear @ 2k rpm. Downshift for anything lower.

And to smooth the transition, I personally hold the clutch for a half a second before fully engaged.

Last edited by Airborne82id; 11-11-2012 at 05:18 PM.
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Old 11-13-2012, 02:42 PM   #19
sharkey62
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Thank you Airborne for your comments. I will try keeping the revs slightly higher than I have been on gear changes and see if it improves.
Thanks again.
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Old 11-13-2012, 03:17 PM   #20
EverydayGetaway
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Quote:
Originally Posted by webster View Post
CDV delete and add a clutch stop from somewhere like UUC or Rogue. simple and easy mods that improve shift feel noticeably. that said, it still will not be as easy to drive smoothly as, say, a Honda manual gearbox. the E46 has a dual mass flywheel and self-adjusting clutch which can make smooth shifts somewhat tricky.
Your logic is extremely flawed. The whole point of the dual mass flywheel and cdv is for smoother shifts...

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