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      04-19-2012, 10:53 AM   #1
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CDV Delete: Experienced Opinions Please

So... I've managed to put off doing the CDV delete for about a year now since I've had my car. At this point, I feel like I'm "pretty good" at working the third pedal now. I've got to get under the car and finish my full bleed (never did the clutch in October) and I'm thinking maybe I'll pull the CDV.

My question to [[people that have mastered their CDV and then removed it is did you notice enough improvement in linearity/feel to say "yeah, I'd definitely do it".

I know there are many CDV delete threads, but wanted to get a concentrated opinion from those who have mastered the beast and then removed it!
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      04-19-2012, 11:39 AM   #2
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Yeah, I'd definitely do it. Hahah....

Seriously though, I did feel I mastered it, although it took a while to get to that point. But I will say after installing the CDV, there definitely was a more linear feel to the whole system, and I am very happy with the way my car is setup now. As I'm sure you've read in all the threads out there, a lot of debate goes on about it, but at the end of the day, I felt it was money well spent, it's totally reversible and it made my driving experience that much better, so I see it as a win for me!
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      04-19-2012, 12:35 PM   #3
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why there is any question about this is beyond me... DO IT. It cant hurt the car unless your trying to i guess, and the feel can only get better. Me and r4gs put my car on a lift and just removed, not replaced, the cdv in the matter of 2 minutes. Just clamp the line that goes into the cdv and hold it tilted upwards so fluid doesnt come out. Pop the cdv out and then put the line back into where the cdv was and done.
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      04-19-2012, 01:26 PM   #4
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Are you an experianced driver?

Clutch delay valves operate as one-way restrictor valves that limit the volume of fluid that can move through the lines in a given time. This ensures a steady quick and firm engagement without being too fast for the drive train to handle since clutches can quickly disengage but re-engagement is damped. The clutch delay valve slows clutch engagement and was intended to reduce drivetrain shock in the event that an inexperienced driver quickly engaged the clutch at higher revs. However for an experienced driver it simply burns and reduces the clutch's life.
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      04-19-2012, 02:40 PM   #5
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Quote:
Originally Posted by davesz4mc View Post
Are you an experianced driver?
Yes I is. I'm a lousy one, but I'm experienced

Seriously though, I was looking for an honest net gain assessment. I'm at a point in my life where I've got little free time (kids still like to do things with me, but also have me driving them all over god's creation) and enough experience working "under the hood" to know that 5 minute jobs can turn into 2 hours at the drop of a bolt or socket.

Nowadays, if there's no reason to mess with something...then I don't.

It's all good.
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      04-19-2012, 02:47 PM   #6
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Quote:
Originally Posted by davesz4mc View Post
Are you an experianced driver?

Clutch delay valves operate as one-way restrictor valves that limit the volume of fluid that can move through the lines in a given time. This ensures a steady quick and firm engagement without being too fast for the drive train to handle since clutches can quickly disengage but re-engagement is damped. The clutch delay valve slows clutch engagement and was intended to reduce drivetrain shock in the event that an inexperienced driver quickly engaged the clutch at higher revs. However for an experienced driver it simply burns and reduces the clutch's life.
Not sure I understand you correctly. So you are saying that the CDV increases clutch wear with experience driver?
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      04-19-2012, 02:47 PM   #7
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I've driven a manual trans car or truck for ~ 15 years. Had an '04 M3 for about 2.5 years. It had a CDV and I never felt like that thing had a predictable clutch. I too felt like I had "mastered it", but it still never felt like it engaged perfectly, especially when driving the car harder. My M coupe came to me with the CDV delete done by the prior owner. Ahhhh - back to a normal clutch. Instantly very different feel and function.

Even if you think you've mastered it, it is a worth while change because of how much more "normal" it acts with that thing out of there. That said, if it's the first and only stick you've ever driven, and you have nothing else to compare to from experience, you probably wouldn't know how much different it could be until you change it out. In general, people who have experience driving manual transmissions for years in different vehicles may appreciate the improvement even more because all of a sudden it will act just like all the previous cars you've ever driven. Until my M3, my first BMW, I'd never heard of a CDV and am quite sure that no other stick trans car of mine ever had one.
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      04-19-2012, 03:09 PM   #8
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Quote:
Originally Posted by onebluemcm View Post
I've driven a manual trans car or truck for ~ 15 years. Had an '04 M3 for about 2.5 years. It had a CDV and I never felt like that thing had a predictable clutch. I too felt like I had "mastered it", but it still never felt like it engaged perfectly, especially when driving the car harder. My M coupe came to me with the CDV delete done by the prior owner. Ahhhh - back to a normal clutch. Instantly very different feel and function.

Even if you think you've mastered it, it is a worth while change because of how much more "normal" it acts with that thing out of there. That said, if it's the first and only stick you've ever driven, and you have nothing else to compare to from experience, you probably wouldn't know how much different it could be until you change it out. In general, people who have experience driving manual transmissions for years in different vehicles may appreciate the improvement even more because all of a sudden it will act just like all the previous cars you've ever driven. Until my M3, my first BMW, I'd never heard of a CDV and am quite sure that no other stick trans car of mine ever had one.
WINNER! I feel like we're twins (except I've got 15 more years manual tranny experience...DAMN, just told you guys that I'm OLD).

Thanks for the great reply.
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      04-19-2012, 04:11 PM   #9
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Cool. So, I definitively will say that you must get that thing out of there - with your driving experience, you will greatly appreciate the improvement. An easy DIY or indy shop modification that is a real no-brainer. Honestly, to the original question, there are so few, if any truly, negatives to removing the CDV that it's really not worth trying to master at all. Just remove the CDV and get on with mastering the car the way it should have been delivered in the first place! I am certain that one of the first things they got rid of on the race car was the CDV. Good Luck!
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      04-19-2012, 04:18 PM   #10
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Reason to not do this mod is if anyone else ever drives your car or if you valet your car.

It's a great mod because it lets you control the clutch directly, rather than having it slowed down on disengagement. It really is a no brainer.

However, I'm not willing to risk the drivetrain damage that someone else can inflict on my car, even though if I can avoid it I don't let anyone else drive it. I still might do this mod in the future.

Just my 2c from the CDV keeping camp If you get used to it, it's really not a huge deal. I've driven stick exclusively for 16 years.
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      04-19-2012, 06:19 PM   #11
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Remove the CDV and you won't ever again think about your clutch..everything will be as it should.
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      04-19-2012, 07:19 PM   #12
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It slows engagment not dis-engagment, letting anyone not used to it may slip the clutch more than not. The reason for it on this car is it may/will jump sideways lots of wheel spin and just flat out leave. With the deley valve it gives you a chance to get out of it at the expense of your clutch. I can see why they put it in there just not any reason to keep it in there =-)
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      04-19-2012, 08:29 PM   #13
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what dave said^

A good example: On the Lancer Evolution the CDV was so obtrusive that if you pulled the clutch out "too quickly" on a launch, the car wouldn't move at all and the flywheel and clutch are just burning up on each other. On the z4 it gives you more play but during normal driving it feels not exactly "right".

As dave said, its done to protect the driveline at the expense of the clutch. Launching a car can be hard on a driveline especially if you connect well at launch. To decrease this fear, the manufacture limits your ability to do this. So in a launch if you were letting the clutch out "quickly" the CDV would make it so that he action is happening less quickly, this translates to more time in which the clutch is only partially engaged and rubbing instead of fully engaged and stuck, decreasing the amount of "shock" on the drive train.
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      04-19-2012, 09:36 PM   #14
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I've had my '99 E46 323i since day one. I've mastered the clutch and can drive it so smoothly like it was an auto. When I got the M Coupe, all of a sudden I felt like I forgot how to drive a manual.

I know you're looking for opinions from people who have mastered the CDV. I tried, I really did, but alternating between my 323i and the M Coupe on a daily or even weekly basis was like Jekyll and Hyde. One day, I'm an expert and the next, I'm a newbie. My wife even noticed it.

Anyway, I removed that silly thing and I'm an expert again.
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      04-19-2012, 10:39 PM   #15
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      04-19-2012, 11:13 PM   #16
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I'm convinced. Out it goes!
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      04-20-2012, 01:16 AM   #17
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It isn't night or day, but is certainly worth doing. I drove my car for about two years, 50 miles a day and the one thing I can say the CDV does is makes the clutch feel unpredictable. One day it is burning the clutch up, one day it grabs. I felt I had mastered it the best one can master a variable.

I took it out and reconnected the line. 97% of all clutch cars out there don't have these things and they seem okay right?

Anyway I highly recommend it, but don't expect it to make a night and day difference.
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      04-20-2012, 06:32 PM   #18
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Quote:
Originally Posted by VitaminT View Post
It isn't night or day, but is certainly worth doing. I drove my car for about two years, 50 miles a day and the one thing I can say the CDV does is makes the clutch feel unpredictable. One day it is burning the clutch up, one day it grabs. I felt I had mastered it the best one can master a variable.

I took it out and reconnected the line. 97% of all clutch cars out there don't have these things and they seem okay right?

Anyway I highly recommend it, but don't expect it to make a night and day difference.
First comment - exactly my thoughts after having an S54 with and one without the CDV.

Second, yeah, a lot of cars with way more clutch burning power that ours probably don't have a CDV. Does anybody know if Mustangs, Vettes, Camaros - all the Big 3 high power cars have them? It certainly can't be about cost because it's an extremely cheap, basic part. I don't get the argument that they put it in there to "protect" the drive train and suspension unless BMW is pretentious enough to think their customers buying manual trans cars can't drive them. Few other manufacturers seem to believe that a CDV is necessary to protect the drive train....

But I digress, and I thread jack - I will stop now....
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      04-21-2012, 12:51 AM   #19
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Check it out

I bought my car ('07 Z4M) a year ago and finally deleted the valve about 6 weeks ago. Like alot of others, I didn't found the difference to be night-and-day.

When I got the car, it did take a few months to really get used to the CDV "helping" with clutch releases and learning to work with it; I found that the timing becomes more instinctive and the interference becomes less noticeable with practice, though it always seems to require more attention (sometimes annoyingly so) to let out the clutch with a CDV than without it.

Taking it out seems to broaden the ranges of revs and corresponding release speeds that you can use and still get a smooth take-off (takes practice again, like the CDV version...no free lunch..) As I'm sure you've figured out, these cars have enough power that they aren't as easy to modulate as lesser beasts whether the valve is in or out (particularly in Sport mode), and taking out the valve doesn't smooth that out as much as I had hoped.

That said, I'm leaving mine out, and I agree that it's easy enough to do that it's worth a test. If you don't mess up the valve i.e. don't punch out the center, etc.), you can put it back in if you don't like it. There are lots of directions posted, some pretty elaborate with decoy valves (for warranty detection purposes), braided lines, etc., but I think that's making it alot harder than it has to be. I just clamped the line, unscrewed the valve, hooked the line up directly in its place (no adapter, other lines, etc.), bled the slave cylinder a little just in case, and DONE.

Last edited by dcoff2; 04-21-2012 at 01:15 AM.
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      04-21-2012, 11:40 PM   #20
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I did mine about a week ago.. I went with the modified CDV.. Before, I felt like I had to make a conscious effort to be smooth shifting from 1st to 2nd and taking off in 1st.. I found myself not enjoying driving around town in traffic.. Now, I just drive.. I feel like I am in total control of clutch engagement.. I love it! I learned how to drive on a manual Triumph Spitfire and a 66 Beetle when I was 15.. Have driven many manuals over the years, but when I got the M last November, I felt like something was "hinky".. It just seemed inconsistent.. I am really glad I did this mod, and have nothing negative to say about it.. BTW , I did the two man (old school) clutch bleed.. How are some of you guys doing it?
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      04-22-2012, 01:49 PM   #21
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Quote:
Originally Posted by MHeavNC View Post
I did mine about a week ago.. I went with the modified CDV.. Before, I felt like I had to make a conscious effort to be smooth shifting from 1st to 2nd and taking off in 1st.. I found myself not enjoying driving around town in traffic.. Now, I just drive.. I feel like I am in total control of clutch engagement.. I love it! I learned how to drive on a manual Triumph Spitfire and a 66 Beetle when I was 15.. Have driven many manuals over the years, but when I got the M last November, I felt like something was "hinky".. It just seemed inconsistent.. I am really glad I did this mod, and have nothing negative to say about it.. BTW , I did the two man (old school) clutch bleed.. How are some of you guys doing it?
Yeah, +1 to this and most everything else posted here. After 2 months of ownership and mastering it enough to still be displeased, I decided: why continue to deal with the CDV in and be frustsrated - after i've been driving a stick for 20 years now. I learned on my older brothers ford escort when I was 15 yrs old (& I waited until I mastered it before I told him I had been 'Borrowing' his car to teach myself, haha!)
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      04-25-2012, 08:00 AM   #22
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Rip that thing outa there! I had my car about 5 years... Plenty of time to master it, on the track and street. I was out of warranty, and getting inspection II, had the cdev removed. Instantly the difference was noticed and appreciated! Much smoother, and more natural. There is no "Transition time"getting used to the couch when I get it out for the summer any more!
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