Clutch Delay Valves - why?
Discussion
Google is your friend
zeckhausen.com said:
The Clutch Delay Valve (CDV) is a one-way restrictor installed by the factory between the clutch slave cylinder and clutch master cylinder, as shown in Figure 1. It "delays" the engagement of the clutch, much like old record players used a damped tone-arm to gently lower the needle onto the surface of a record.
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 driveline from shock, were an inexperienced (or immature) driver to dump the clutch at high RPM. But in practice, all it does is prematurely wear out the clutch and turn experienced drivers into people who, despite 20 years of practice, cannot shift gears smoothly. During parallel parking maneuvers, the delay can be infuriating, causing constant clutch slippage. And during hard acceleration, the large amount of clutch slippage can greatly shorten the life of your clutch.
more here: http://www.zeckhausen.com/CDV.htmBecause 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 driveline from shock, were an inexperienced (or immature) driver to dump the clutch at high RPM. But in practice, all it does is prematurely wear out the clutch and turn experienced drivers into people who, despite 20 years of practice, cannot shift gears smoothly. During parallel parking maneuvers, the delay can be infuriating, causing constant clutch slippage. And during hard acceleration, the large amount of clutch slippage can greatly shorten the life of your clutch.
Edited by Simbu on Tuesday 5th January 11:37
To stop you dumping the clutch and sending a shock load through the driveline that would break it, thus enabling you to spec a lighter/quieter/cheaper driveline that's adequately robust for normal road driving, but wouldn't survive a single drag spec launch.
We've done this before haven't we?
We've done this before haven't we?
RobM77 said:
Why do clutch delay valves exist on cars? The downside is that they make it harder to change gear smoothly; what's the upside?
The upside is earlier clutch failure for the manufacturers. These along with the utterly unnecessary DMF shows that no matter how much engineers learn they can still be fundamentally stupid.reg_slr said:
RobM77 said:
Why do clutch delay valves exist on cars? The downside is that they make it harder to change gear smoothly; what's the upside?
The upside is earlier clutch failure for the manufacturers. These along with the utterly unnecessary DMF shows that no matter how much engineers learn they can still be fundamentally stupid.TheRoadWarrior said:
Probably less to do with the engineers and more to do with management!
No more than any other feature of any car. It's an engineering compromise. Some would see it as a get out of jail free card for a lighter and smoother driveline without increasing risk of warranty claims from muppets who lunch diffs while launching their cars.
The vast majority of drivers wont even know it's there, but might notice if their car has a lot of shunt or transmission whine.
I personally think it's a short cut cost cutting method, but it's only an opinion, and everyone has their own.
Blame the market research that defines the decision making process of the engineers, not the engineers themselves. I've worked on some utterly ridiculous projects in the past that were plainly never going to be viable, but if the client wants it through some peculiarity of internal politics (*cough* germans) or outcome of a customer survey, then the client gets it.
Edited by The Wookie on Tuesday 5th January 12:29
Thanks for your responses, and sorry if google could have answered the question. I was keen on hearing the PH opinion and a bit of insight.
My car's under warranty so I don't want to remove it, and it doesn't wind me up that much. I was just driving my car for the first time in a few weeks and I wondered why the damm thing existed in the first place! In my Lotus I could drive a sleeping baby holding a hot cup of coffee without a problem; no way in the BMW. It just seems to me that BMW have deliberately made their car harder to drive for 90% of people so that 10% of people who are rubbish drivers can cope (and are probably driving Micras anyway).
My car's under warranty so I don't want to remove it, and it doesn't wind me up that much. I was just driving my car for the first time in a few weeks and I wondered why the damm thing existed in the first place! In my Lotus I could drive a sleeping baby holding a hot cup of coffee without a problem; no way in the BMW. It just seems to me that BMW have deliberately made their car harder to drive for 90% of people so that 10% of people who are rubbish drivers can cope (and are probably driving Micras anyway).
Gaygle said:
I have it on me 330i Sport and it can make low speed town driving a bit more "shunty". I would like to take it off but i really can't be bothered.
I removed it from my 330i Sport and it makes the gearchange so much smoother. I couldn't get on with the gear change prior to doing this.A pretty easy job, I put some new fluid through mine along with putting new fluid through the brakes just to be sure.
I've just been reading through the information at http://www.zeckhausen.com/CDV.htm and I'm really tempted to do replace my CDV. It seems simpler than I'd thought, and I like the fact that the car doesn't look modified in any way.
minghis said:
I'm staggered these things exist.
What is happening to modern cars - dual mass flywheels, significant delays on fly by wire throttles, can't brake and use the throttle at the same time and now clutch delay valves.
Racing cars are fine, but road cars are becoming a nightmare. Manufacturers accept that Joe Bloggs wants to get to work safely and cheaply, and that Jenson Button wants to win races and not crash. Road car enthusiasts have been left in the middle somewhat, stuck trying to get some enjoyment out of cars designed for Joe Bloggs.What is happening to modern cars - dual mass flywheels, significant delays on fly by wire throttles, can't brake and use the throttle at the same time and now clutch delay valves.
There's some hope though. I've driven a lot of modern performance cars and Caterham (cable throttles and normal clutches) and Lotus (carefully designed DBW and normal clutches) are still ok. It's a shame we've "lost" BMW (CDV, DBW, DMF) and Porsche (DBW, and that awful non linear steering), because they make cars we can drive every day in comfort, but maybe one day things will improve. DBW has also come on leaps and bounds since it was first introduced. For instance the latest BMW 330 is in a different league of driveability to the MY 2000 330, which introduced all these gizmos.
RobM77 said:
I've just been reading through the information at http://www.zeckhausen.com/CDV.htm and I'm really tempted to do replace my CDV. It seems simpler than I'd thought, and I like the fact that the car doesn't look modified in any way.
You don't even need to do that, just remove it. The end of the existing clutch pipe connects up just fine without a replacement. 20 minute job by a decent garage (need to run the fluid through/bleed).99.9% of people won't even know to look for the valve - and unless you have a BMW warranty just removing it is a non-issue. I bet when you come to sell that any test drivers comment on how slick your drivetrain feels compared to other (CDV equipped) cars they have test driven.
Edited by Targarama on Tuesday 5th January 14:31
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