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M2 Technical Topics > N55 Engine / Drivetrain / Exhaust / Bolt-ons / Tuning > Clutch Delay Valve Removal DIY

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      08-26-2019, 03:54 PM   #23
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Quote:
Originally Posted by jkoral View Post
From https://www.zeckhausen.com/catalog/index.php?cPath=6562

"Due to this factory device, the clutch engages the flywheel slowly, regardless of how quickly you lift off the clutch pedal. In theory, it reduces driveline shock, if an inexperienced driver dumps the clutch. In practice, it prematurely wears the clutch disc and transforms experienced drivers into novices, who cannot shift smoothly."

(I did this on my E46s and E82 and plan to do the same for my new to me OG M2).
I don't think the difference on the F-series cars is as pronounced as it was on the E-series. Not having driven an E-series before and after though, I don't have any basis for comparison.

As I said before, I also think there is a difference between an F-Series M car and an F-Series non-M car. There was absolutely no slipping with my M2 with the CDV in place, and I could easily get the wheels to chirrup changing 1st to 2nd.

Although now I've done it, I'd class this mod as a 'must have / do', there must be a reason that hardly anyone complained or found a solution until relatively recently...
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      09-01-2019, 01:05 AM   #24
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Wow, I was wondering what was going on. The revs drop SO quickly no matter what i did and I could not figure out what I was doing wrong. Ive had 8 manual transmission cars back to back over the past 20 years(most not fancy) and I was beginning to wonder why I could not consistently shift this car smoothly. This feels more pronounced than on the e90 m3 but it could be my imagination.

Last edited by srmast1; 09-01-2019 at 01:29 AM..
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      09-03-2019, 11:01 AM   #25
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Thank you so much for taking the time to write this up.

This utter POS CDV makes normal driving with the 6MT needlessly jerky and clunky. I've been driving manuals for three decades now and this is by far the most difficult manual to drive smoothly. The CDV really makes you have to think about clutch modulation and it can make the catch point move around a bit. It's as if BMW intentionally added this device to push people towards buying automatics. I've owned this car for 3.5 years now and it is by far my biggest complaint with my M235 6MT (same tranny as the M2).

The intended purpose of the CDV is to reduce hard shift shock and drivetrain damage on hard shifts. Oddly, when driven in anger, I find that the 6MT is exceptional. I can slam gears hard with a nice firm and direct shift and engagement. I can tell the clutch is robust and sometimes a strong clutch can make engagement difficult, but the CDV is the main culprit for the issues I have.

I've learned that the smoothest way to shift is to delay the 1-2 and 2-3 until ~3,500rpms. Shifting earlier than that makes it difficult to execute smoothly. Shifts 3-4 and above aren't a problem.

The CDV delete is high on my list. I do worry about the bleeding though. Seems like a pain.
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      09-15-2019, 02:12 PM   #26
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Thanks for this topic
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      09-16-2019, 03:59 PM   #27
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Quote:
Originally Posted by XutvJet View Post
Thank you so much for taking the time to write this up.

This utter POS CDV makes normal driving with the 6MT needlessly jerky and clunky. I've been driving manuals for three decades now and this is by far the most difficult manual to drive smoothly. The CDV really makes you have to think about clutch modulation and it can make the catch point move around a bit. It's as if BMW intentionally added this device to push people towards buying automatics. I've owned this car for 3.5 years now and it is by far my biggest complaint with my M235 6MT (same tranny as the M2).

The intended purpose of the CDV is to reduce hard shift shock and drivetrain damage on hard shifts. Oddly, when driven in anger, I find that the 6MT is exceptional. I can slam gears hard with a nice firm and direct shift and engagement. I can tell the clutch is robust and sometimes a strong clutch can make engagement difficult, but the CDV is the main culprit for the issues I have.

I've learned that the smoothest way to shift is to delay the 1-2 and 2-3 until ~3,500rpms. Shifting earlier than that makes it difficult to execute smoothly. Shifts 3-4 and above aren't a problem.

The CDV delete is high on my list. I do worry about the bleeding though. Seems like a pain.
I've found short-shifting at ~1.5k RPM 1st to 2nd is pretty smooth. Anywhere between 2k-3k RPM is extremely jerky unless I wait a good 1-2 seconds for the revs to come down (which causes the car behind me to end up right on my bumper because they don't expect me to stop accelerating for that long).
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      09-16-2019, 05:49 PM   #28
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Man, I knew something was weird with the clutch release on this car. Makes total sense now!
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      09-16-2019, 10:11 PM   #29
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Quote:
Originally Posted by XutvJet View Post
Thank you so much for taking the time to write this up.

This utter POS CDV makes normal driving with the 6MT needlessly jerky and clunky. I've been driving manuals for three decades now and this is by far the most difficult manual to drive smoothly. The CDV really makes you have to think about clutch modulation and it can make the catch point move around a bit. It's as if BMW intentionally added this device to push people towards buying automatics. I've owned this car for 3.5 years now and it is by far my biggest complaint with my M235 6MT (same tranny as the M2).

The intended purpose of the CDV is to reduce hard shift shock and drivetrain damage on hard shifts. Oddly, when driven in anger, I find that the 6MT is exceptional. I can slam gears hard with a nice firm and direct shift and engagement. I can tell the clutch is robust and sometimes a strong clutch can make engagement difficult, but the CDV is the main culprit for the issues I have.

I've learned that the smoothest way to shift is to delay the 1-2 and 2-3 until ~3,500rpms. Shifting earlier than that makes it difficult to execute smoothly. Shifts 3-4 and above aren't a problem.

The CDV delete is high on my list. I do worry about the bleeding though. Seems like a pain.
I am interested to see when you remove it if it has the effect you think it will have. My experience with CDV on Z4M is that it did not really make the shifts any smoother or change the catch point, but did improve modulation from a stop and in reverse. The catch point moving is a different problem, I think. I didn't have any movement of the catch point on the Z4M even with CDV. I have noticed this on newer cars like my Mazda 3 6MT, though. I think it's just the self adjusting clutch.
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      10-04-2019, 12:55 PM   #30
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Great write-up, although I'm still not sure how to remove the CDV itself from the slave, I may be a spare slave so that I can do it all on the bench and take my time...

Thanks for the effort!
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      10-10-2019, 12:31 PM   #31
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Thanks for the write-up. Surprised to see CDVs on M cars! Added to my list of to-dos.
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      11-19-2019, 04:49 PM   #32
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Quote:
Originally Posted by LuvMyE92 View Post
Great write-up, although I'm still not sure how to remove the CDV itself from the slave, I may be a spare slave so that I can do it all on the bench and take my time...

Thanks for the effort!
This may be an option for you: https://f30.bimmerpost.com/forums/sh....php?t=1666477
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      11-20-2019, 07:16 AM   #33
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Quote:
Originally Posted by Daytona_550 View Post
Yeah, I also found that thread and it seems like a much easier and "cleaner" way to go. I was driving the car yesterday and it seemed like every time I used the clutch I was thinking "this could be better". I need to get off of my lazy butt and just do it.

I wish I had a lift.
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