[850CSi]

So it's that CDV...

It's bothering the hell out of me.

[MTMnet]

I think it is just an issue of speed matching. The new, tight engine drops its rpms so fast its hard to get the clucth out fast enough before the RPMs drop too far down.

Of course, if you wind the RPMs up nice and high before shifting, you have much better chance of getting it right and having a nice smooth shift......I hope that makes sense.

Once I get past the break-in period and can wind the engine out a bit, the smoother shifts will come easier!

[850CSi]

"Because of this valve, no matter how quickly you lift your foot off the clutch pedal, the clutch engages the flywheel at a constant (slow) rate. In theory, it can save the drive train from shock, were an inexperienced (or teenage) driver to dump the clutch at high RPM."

Does it really work that way?

It's not that bad if it does, because the delay won't be long, I'm sure, and it means you don't have to bother with making a smooth clutch disengagement.

Could that be why the few times during the break in period when I really had to floor it and execute a quick redline shift they actually turned out to be smooth?

I'm gonna try it tommorrow.

[JamieA]

I have been getting into the rhythm of it, and I must say that the short shifting you have to do during run in makes the problem worse. When I shift at higher RPM it is easy to get them smooth as silk.

I have to say, the engine is VERY responsive, almost like it has no flywheel because the revs drop real quick. I have been compensating for this during run in shifting by leaving my foot on the accelerator a bit while the clutch is out to moderate the rate the RPMs fall.

[visor]

From trial and error, I have found shifting to be much smoother and faster if I apply just a little bit of pressure on the shifter (in the direction of the throw) just before I clutch and then complete the shift.

By doing this, there is less hang time for the engine revs to fall, and I don't need to hang on to the gas pedal at all.

[JamieA]

Thanks Visor, I will give that a go!

[Xens]

Rev-matching, that's it.

On other manual cars I've driven/practiced on, you only need to rev-match when downshifting, but E90 MT requires me to rev-match when upshifting as well.

This is my first manual, have about 2000 miles on it now and I rarely jerk anymore. It was a lot for a newbie to learn but I liked the challenge.

[850CSi]

Originally Posted by JamieA

I have been compensating for this during run in shifting by leaving my foot on the accelerator a bit while the clutch is out to moderate the rate the RPMs fall.

Isn't that going to wear down your clutch in record time?

[850CSi]

Originally Posted by Xens

Rev-matching, that's it.

... And it's making it hard to drive the E90 economically...

[petesamprs]

Originally Posted by RichReg

The CDV prevents the novice from screwing up the transmission by accidentally shifting into the wrong gear or shifting improperly. It also prolongs clutch life.

I'd still like to try out Zeckhausen's CDV though.....

Rich -
This is not correct. The CDV SHORTERNS clutch life, in order to protect the drivetrain, due to slower clutch engagement and therefore extra clutch wear.

My car arrived yesterday and I've already contacted Dave to get my CDV replaced. Unfortunately he's not able to work on the e90 due to the extensive underside body panels, but he gave me the name of someone who could.

[850CSi]

Originally Posted by petesamprs

Rich -
This is not correct. The CDV SHORTERNS clutch life, in order to protect the drivetrain, due to slower clutch engagement and therefore extra clutch wear.

That's what I'm thinking. Certainly makes a lot more sense to me.

[vladinecko]

a quote from zeckhousen:

In theory, it can save the drive train from shock, were an inexperienced (or teenage) driver to dump the clutch at high RPM. But in practice, all it does is accelerate wear on the clutch and turn experienced drivers into people who, despite 20 years of practice, cannot shift gears smoothly.

i especially like the part about 20 years of practice. so what the hell are people with 0 years of practice suppose to do?

[850CSi]

It comes more natural to those who are learning. People like us are used to the control we get from a manual and how to make smooth, fast shifts. They don't know what it's like to drive a normal clutch and they get used to a CDV-infested one.

[850CSi]

You know what...


I don't know if this'll get me anywhere, but...

I'm going to try writing a letter to BMW NA complaining about this thing.

Honestly, all I want is my 'valve taken out by a dealership without any warranty trouble.

[ben1364]

We should give BMW a bit of credit for even making manual transmissions available throughout most of their product range. Most manufacturers and importers of luxury and near luxury (priced) vehicles have discontinued the manual option. Having said that, the CDV is in my opinion another case of BMW designing a solution to a problem that doesn't really exist.

[JamieA]

Originally Posted by 850CSi

Isn't that going to wear down your clutch in record time?

No, it is rev-matching not flat shifting. It is the oposite to the heel toe method to blip the throttle on downshifts... same thing, just the oposite direction to what I do when shifting up.

The engine is spinning with the clutch disengaged, does not cause wear, the crucial moments are disengagement and engagement. Obviously I don't rev it as I disengage, I feather the throttle then hold the revs after the clutch is in.

Conversely rev matching is better for clutch wear when engaging, because you don't have the driveline snatching at the clutch so much.

[Will L.]

I don't really know much about rev matching, flywheels etc. All I know is I've never owned an automatic, and after 24 years, this is the smoothest, easiest shifting manual I've ever driven.

I've had a few rough 1-2 shifts under hard acceleration, and if you're unfamiliar with the car and/or hesitant, that could cause problems, but if you're considering not buying the manual because you're afraid the transmission is inherently rough, I don't think you need to worry.

Good luck!

[JamieA]

I have to say that shift quality is much better than I expected after reading previous threads on this while I was waiting for my car.

If I think about it too much it isn't as good as if I just stop thinking about it and shift subconsciously. I have never owned an auto, and don't plan to in the near future.

Drive a Hyundai manual and then you will know bad shift quality, the one I drove in the mid 90's (it was a partner's, not mine BTW) was like trying to change gears with a blow up banana.

[silverado]

Originally Posted by JamieA

Drive a Hyundai manual and then you will know bad shift quality, the one I drove in the mid 90's (it was a partner's, not mine BTW) was like trying to change gears with a blow up banana.

VERY funny!

[silverado]

Two points:

First, I think this car's fine characterists of being so smooth and quiet yet delivering such crisp feel to the driver about everything that's going on results in the slightest imperfection of shift timing to be felt by the driver. In other words, feeling an imprefect shift every now and then is more a testament to the excellence of the car than difficulty of shifting. I bet in most other cars, such imperfect shifts would be impreciptible to the driver and passengers because they would be diluted into the "slop" in feedback.

Second, in addition to different levels of eperience, people obviously vary in expectations and sharpness of perception, which could account for some of the different opinions we see here.