BimmerFest BMW Forum banner
1 - 20 of 92 Posts

·
Registered
Joined
·
225 Posts
Discussion Starter · #1 ·
I'm now determined to learn how to shift smoothly with the CDV. The guys at BMW must have had a good reason to put this thing in, right? So somebody over there in the BMW lab is using it, using it well, and thinks it's a great idea. So what's the technique? How are you supposed to engage the clutch with the CDV so that it does whatever it's supposed to do?

#750 (This is driving me crazy)
 

·
Registered
Joined
·
1,162 Posts
I thought it was the "self-adjusting clutch" part.
There was a theory posed that suggested the cdv protects the driveline from shock.
With the cdv in place, you don't let the clutch out all the way all the time. Instead, you let it out and hold it near the top of its travel then let it the rest of the way. Doing it this way will give smoother shifts at the cost of wearing out the clutch methinks.
 

·
Rest in peace, Coach
Joined
·
9,106 Posts
The CDV allows you to let out the clutch in one quick motion and buffer the impact it has on the remainder of the drivetrain as the clutch engages. Without the CDV, if you shift quickly and "dump" the clutch in one motion you will not get clutch slippage, and if your RPM isn't in the right range and/or if your throttle input isn't right, you either get a bucking sensation as the car takes off or the engine slows the car down. With the CDV present, if your RPM is too high or too low and you let the clutch out quickly, it's buffered and all you'll feel is a little light "chirp" from the clutch, some slippage, and the car will go on about its business in a merry way with less of that bucking sensation.

The theory I subscribe to, is that BMW feel it's easier to replace the clutch than it is to replace the transmission, so that with the CDV installed, the clutch will burn out first but the remainder of the system will be spared. Since the "warranty" does not cover wear-able items like the clutch, brakes, and tires, they'd covered in that this shift the failure to the clutch instead of the transmission and they don't have to be financially responsible for damages.
 

·
Registered
Joined
·
304 Posts
I wonder if you had a transmission failure of some sort, and the CDV was removed, I wonder if they would not honor the warrenty for that repair. Beings the car was altered. Just speculating.
 

·
Officially Welcomed To The 'Fest!
Joined
·
355 Posts
rogue38 said:
I wonder if you had a transmission failure of some sort, and the CDV was removed, I wonder if they would not honor the warrenty for that repair. Beings the car was altered. Just speculating.
I have read a number of posts speculating that, but have never heard from anyone who had that experience.
 

·
Rest in peace, Coach
Joined
·
9,106 Posts
rogue38 said:
I wonder if you had a transmission failure of some sort, and the CDV was removed, I wonder if they would not honor the warrenty for that repair. Beings the car was altered. Just speculating.
Of course not. Modifying the CDV, a part of the drive-train, can easily be attributed to whatever transmission failure and BMW can surely deny you warranty claim, if they choose to.
 

·
takes the long way home..
Joined
·
1,080 Posts
Something to keep in mind- a number of E46 325s and 330s were coming from the factory w/o them. And many M3s came with the CDV, even though it's not supposed to have it.

To me the logic behind the CDV is similar to the smaller diameter anti-sway bars that come from the factory with understeer dialed in. The avg driver will react to understeer by hitting the brakes, but with oversteer they don't know to lift off the gas and not hit the brake. Perhaps another reason the ZHP has stiffer bars.

Same idea with the CDV. The CDV drops the bar to the lowest common denominator of people that actually drive the car. Uncoordinated people who use the clutch pedal as they do the throttle.

Can I change my username to CDVfree ;)
 

·
Registered
Joined
·
564 Posts
I've never asked about the CDV issue before, but I have read a lot on these pages. Would the CDV be responsible for that light clunk I feel when shifting from first to second quickly? Seems when I do the whole process slowly, it's all good.
 

·
Rest in peace, Coach
Joined
·
9,106 Posts
Jim H said:
I've never asked about the CDV issue before, but I have read a lot on these pages. Would the CDV be responsible for that light clunk I feel when shifting from first to second quickly? Seems when I do the whole process slowly, it's all good.
No.
 

·
Rest in peace, Coach
Joined
·
9,106 Posts
shizat63 said:
...but with oversteer they don't know to lift off the gas and not hit the brake. Perhaps another reason the ZHP has stiffer bars...
That will result in terminal oversteer. You do not EVER want to lift off the gas. In most cases, you actually need to apply more throttle and counter-steer, or EASE very slightly off the gas pedal. A "lift" will immediately snap the rear end around, especially if you have DSC turned off and the traction is low.

A fine line that they always teach at driving schools, is that all your pedal inputs needs to be "paper thin", especially at the edge of car's grip levels. "Lifting" is a dirty word to use. At 6,000 RPM, a mere 2mm movement in the pedal one way or another can dramatically alter the behavior of the car.
 

·
Registered
Joined
·
564 Posts
The HACK said:
OK, so am I just being brainless? I've driven manual transmissions since I first started driving, have NEVER worn out a clutch before 130k miles (and then only once), and before my e46 had never had trouble making nice and smooth 1-2 shifts very quickly. So what am I doing wrong?
 

·
takes the long way home..
Joined
·
1,080 Posts
Jim H said:
OK, so am I just being brainless? I've driven manual transmissions since I first started driving, have NEVER worn out a clutch before 130k miles (and then only once), and before my e46 had never had trouble making nice and smooth 1-2 shifts very quickly. So what am I doing wrong?
By 'clunk' are you referring to when you shift into 2nd? Or do you mean when you lift off the clutch and the car lurches? If it's the latter, then yes it's the CDV.
 

·
Rest in peace, Coach
Joined
·
9,106 Posts
Jim H said:
OK, so am I just being brainless? I've driven manual transmissions since I first started driving, have NEVER worn out a clutch before 130k miles (and then only once), and before my e46 had never had trouble making nice and smooth 1-2 shifts very quickly. So what am I doing wrong?
Is this your first BMW? And if so, what other manuals did you use to own?

If not, I don't know what to say. My Z3 used to clunk when I shift from first to second, mainly due to the slack in the drive-line and the mechanical shifter linkage. I've driven some cable based linkages, and most of them don't make that mechanical sound. My current ride has a mechanical linkage as well and it clunks between 1st and 2nd.
 

·
Registered
Joined
·
564 Posts
shizat63 said:
By 'clunk' are you referring to when you shift into 2nd? Or do you mean when you lift off the clutch and the car lurches? If it's the latter, then yes it's the CDV.
Well, I've noticed both symptoms not that I think of it. But I was referring to the shift into second. This has never been an issue for me before. Of course, the car is still relatively new, so I'm getting used to it. Just trying to figure out what I'm doing that's causing it. Never happened on my e30.
 

·
takes the long way home..
Joined
·
1,080 Posts
Jim H said:
Well, I've noticed both symptoms I guess. But I was referring to the shift into second. This has never been an issue for me before. Of course, the car is still relatively new, so I'm getting used to it. Just trying to figure out what I'm doing that's causing it. Never happened on my e30.
My post about the 2nd gear clunk: http://www.bimmerfest.com/forums/showpost.php?p=1117853&postcount=4
 

·
•••••••
Joined
·
16,117 Posts
Jim H said:
OK, so am I just being brainless? I've driven manual transmissions since I first started driving, have NEVER worn out a clutch before 130k miles (and then only once), and before my e46 had never had trouble making nice and smooth 1-2 shifts very quickly. So what am I doing wrong?
The E46s clutch is definitely more 'numb' than most I've driven... smooth shifts become more a matter of developing muscle memory than searching for the engagement point by feel.

I was pretty rough-shifting in mine for a few months... but I'm not any more.

Getting a clutch stop will help in establishing that muscle memory, too... less travel = easier to find (and "memorize") engagement point.
 
1 - 20 of 92 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top