Dual Mass Flywheels - Information

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vince
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Post by vince »

Am i in favour? ......well im of the school of thought that the car should be replaced with what it was designed to run with. Reason being is that millions were spent in the design process to achieve the best from the vehicle with the components fitted.

I guess its like the Xantia Matrix situation......the design is good and many last for ages, however if you neglect coolant changes as per outlined then it will prematurely fail.

know there are some advantages but i cant see why a normal clutch wouldnt be just as good and more reliable

This was discussed with the size of clutch and the limit in the number of springs able to be fitted within it. DMF's were apparently designed because in the testing process of the prototype vehicles the conventional clutches could not perform effectively enough or reliably enough.

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rabenson
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Post by rabenson »

There have been times, though in the development of modern cars, when innovations have been introduced before the technology was really adequate. I think that most people would agree that car based computer networks are now pretty stable and research has shown that they have improved reliability - (still a sod when they go wrong...), but they were a nightmare when they were first introduced (early comm2000 etc...). Early particulate filter systems have caused many problems but now seem to be reliable (or so I've heard). I wonder if many of the problems with premature failing of early DMF systems will become a thing of the past as devices are improved and modified in response to these problems.... This is a problem with being at the cutting edge, and PSA generally tend to use citroen as a test bed for technologies that later appear across the group...

Citroenmad
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Post by Citroenmad »

Yes that might be a good point, they might become more reliable. Though at a guess id say a lot of new cars will have them fitted now, and most diesels will have them. So they cant be too bad if so many cars use them.

My opinion is still id rather not have one, if a car i had with a DMF needed the flywheel replacing i would look to see if there is a solid flywheel option. Though you have made me think that these might not be 100% reliable either. Though the C5 one seems fine, its a good quality kit, and was fitted way before i bought the car.

Still if this is progress, then so be it ....

Sid_the_Squid
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Joined: 21 Apr 2009, 15:35

Post by Sid_the_Squid »

Chris I think your point about the C5 engine and drive train being originally designed with a solid flywheel, then having a DMF fitter later, might be why its absolutely fine going back to a solid fly wheel. I suspect problems with engines & drive train as a result of replacing a DMF with a solid conversion would really effect cars designed from the ground up to have a DMF and the reduced level of vibrations that accompany this tech. I also think rabenson has a very good point about the early revisions of any technology feature sometimes being less than reliable, happens quite a lot, many things happen in real every day use, which manufactures simply cannot predict nor test for, the result seemingly unreliable tech, until improvements are made in subsequent revision, hopefully the product image is not to badly tarnished in the mean time.
Also bear in mind Vinces point about garage ignorance fueling the rumors that DMF's are flawed, consider our beloved hydraulics suspension system, how many garages don't understand, and thus the general view is Citroens with that wacky suspension, oh their daft and unreliable don't touch em*.

I would assume we are now past the 'beta testing' period, of DMF as a product, life cycle, going forward maybe DMF's will be just as relyable as conventional flywheels, time will tell.


*some advice I was once given :roll:


Vince thank you very much for the insights, keep sharing this kind of invaluable information with us :)

xmexclusive
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Joined: 18 Dec 2008, 23:50

Post by xmexclusive »

Hi All

Car manufacturers control vibration levels for two reasons; for driver/passenger comfort in the vehicle and for component working life.
It is the component working life that interests me. Pass a vibration threshold and we are into fatigue crack growth problems. Manufacturers do extensive testing to avoid fatigue crack problems. There is an assumption in this thread that just because a particular engine type has previously been supplied fitted with an old type clutch that it is exactly the same engine with the same fatigue strength components as a much later produced engine supplied fitted with a DMF. It needs to be borne in mind that manufacturers continuously modify components to lower costs. Before deciding to modify the clutch from standard I would be inclined to spend a little time making comparision checks between the two engines, particularly crank shaft and drive train components for critical changes.

John

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rabenson
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Re: Dual Mass Flywheels - Information

Post by rabenson »

vince wrote: Although these are expensive assemblies, they are designed to last in the region of 200K miles on a vehicle driven in the correct gear for engine conditions, not ragged up and down kirbs and over speedbumps which add extra sudden vibrations to the drivetrain, and not driven off from rest in too high a gear which increases judder.
I wonder if there's any benefit in dipping the clutch as you drive over a speedbump? I only say this as my route to work on central Middlesbrough is turning into speedbump central......... :shock:

vince
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Post by vince »

Possibly? Im not sure.....

They said the biggest killer of DMF's was setting off in too high a gear for example starting from rest in second gear etc where the car literally shudders as it picks up speed and also bouncing up and down kerbs.

Just to clarify, on the DMC kits (aftermarket conversion kits) They didnt state that the kit itself was morte prone to failure, moreso that other components were prone to failure....driveshafts, engine mounts, gearboxes etc. But the biggest problem with them was / a parts place will not be able to match you a clutch up if the clutch part of the conversion kit wears out with routine use. They have a special size clutch for the kits which is not your vehicle's standard size....so you end up having to buy a complete kit again :wink:

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Kowalski
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Post by Kowalski »

vince wrote:so you end up having to buy a complete kit again :wink:
Just how many clutches are you planning on wearing your way through? :lol: