Dual Mass Flywheels - Information

This is the place for posts that don't fit into any other category.

Moderator: RichardW

Post Reply
vince
Posts: 1409
Joined: 22 May 2008, 22:29
Location: oldham
My Cars:
x 13

Dual Mass Flywheels - Information

Post by vince »

Ok guys, for anyone mystified by the DMF's fitted to later model vehicles, here is what they are all about and also information about aftermarket solid flywheel conversion kits.

Firstly. the below information was aquired after a full day site visit and product information seminar at LUK headquarters yesterday. It is not my personal statement and therefore should only be viewed as an informational source.
What is a dual mass's purpose? = An extension of the shock absorbing springs found in the clutch friction plate. - An extra shock absorber in effect.

Why technology has changed to DMF's from solid flywheels......
Due to the demands of customers and the global marketplace on car manufacture, everyone now demands a car that can do everything.....it must be good on fuel, have strong power levels, be smooth and quiet, have longevity, and have a high equipment spec, A/C, P/S, SatNav, etc....all at a price thats right. Also vehicle demand has taken off in the diesel direction.

As such cars are now bigger than before (to provide the space and comfort of market demand, and also to be able to fit all the equipment into them that people want). This has increased vehicle weight and oils have been made thinner to comply with smaller engine tolerances in the drive towards increased fuel efficiency.

To achieve this, powertrains have had to be made lighter using less dense metals....As the basic induction compression power and exhaust cycle hasnt changed, the same vibrational forces are generated in the engine's internals as have always been the case. These then travel through the crank into the box, through the drive train and into the passenger cabin. Manufacturers found that as vehicles progressed they required a bigger clutch plate to stop increased vibration transfer through the drivetrain and into the cabin. As there is only so much room underneath a vehicle to increase the size of a bellhousing to accomodate a bigger clutch assembly, and as you can only fit so many springs into a conventional clutch plate, the DMF was born via LUK. It is, a solid flywheel with an inbuilt slider mechanism that rotates between 29% and 130% with springs built into its circumference to absorbe the extra shock put through the drivetrain....This then solved the problem of space restrictions, and provided the solution of increased damping.

Due to the complexity of the product, productions costs are not cheap, hence the units are not cheap..... Other vehicle manufacturers had no choice but to fit these if they wanted to compete with others fitting them.

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.

A few companies have tried to pioneer DMF recon'ing but have realised that it cannot be done at a cheaper cost than a new DMF replacement.

As LUK pioneered the technology and production of the DMF worldwide, other conventional clutch manufacturers faced the future of decreased global sales as vehicles got older and newer vehicles moved to DMF set ups which they could not offer replacement parts on. As such deliberate slander campaigns were designed and set off to try to draw manufacturers and customers back to the old technology conventional clutch set ups. This would then secure future business for these other companies.

As a way back into the marketplace, the DMC kits were born. Dual Mass Conversion Kits.

These are frankenstein kits that replace the DMF clutch assembly with a solid flywheel set up...however these are pre assembled kits, and not conventional clutch set ups like on older vehicles.

The attraction of these kits are that they are cheaper than replacing a clutch and DMF assembly. There are however things to know about them....

When the friction surface wears out it is very difficult to obtain a new friction plate for it unless the make of the replacement kit is known and the manufacturer can id which type was fitted into that kit and supply it. If the vehicle was bought second hand with the conversion fitted, often a complete new conversion kit needs to be fitted again.

At this point again i reiterate that i dont work for LUK and this info is meant to be just that...an information source, not my personal account of DMF's and DMC's

Irrespective of common market gossip (see the above slander campaigns by non DMF equipped companies) Conversion kits cannot eliminate the vibrations caused by the above changes to vehicle design and manufacture and yes other things can suffer. Firstly on transits...more fleet companies are finding premature crank pulley failure and first motion shaft bearing failure due to the decreased damping offered. And also highlighted are Skoda Octavias being known to sever driveshafts as often as every 12K miles, and 1.9TDI VAG models such as the mark 4 Golf experiencing gearbox failures........

End
As Dave was it said, he hasnt noticed much of a change on his HDI C5's with the DMF and DMC fitted. Perhaps this is because they are a vehicle primarily designed for optimum comfort levels as most french cars are? Who knows...?

This perhaps will prompt some discussion....... :P

P.s. I didnt know that LUK clutches can incorporate Valeo friction surfaces inside them. Apparently there is a good alliance between the two companies as they share the same equal passion for optimum OE standard components.
Last edited by vince on 23 Oct 2009, 21:54, edited 2 times in total.
1993 Citroen xm 2.1td, silver/grey, bowling ball wheel trims, 210k and climbing...
Citroenmad
Posts: 8125
Joined: 04 Dec 2008, 22:08
Location: Northeast
My Cars: 07 Citroen C6 V6 HDi Exclusive - Red
07 Citroen C5 HDi VTR - Red
09 Citroen C3 1.4i VTR - Silver
01 Citroen Saxo 1.1i Forte - Mango Orange
93 Ford Mondeo 2.0i GLX
19 Hyundai i10
x 110

Post by Citroenmad »

I know you have not finished your post yet ... hope your feeling better soon! ... and your info will be far more factual than my opinions, however:

I had thought cars with DMFs didnt have the conventional springs inside the clutch friction plate, they rely mainly on the spring mounts inside the DMF? This is the bit which usually fails (i believe rubber mounts are often used?) and shortens the clutch life even though the friction plate is still good.

I also believe that some car manuafacturers are now moving away from DMF again as they are become very unreliable.

This is a very common thing to fail on new cars, especially as a lot of people abuse the clutch and use it as a brake at junctions to hold the car. Though the DMF can fail without this punishment.

My C5s DMF failed at 60ishK miles, even though its owner from new is an IAM instructor and didnt abuse the clutch. It now has a solid flywheel fitted, thank goodness!

It was interesting to see how our old C5 Estates clutch compared to the one in my hatch, both had the same engines but one with a DMF and the other without. The one with had a lower bite point and was a little more forgiving if a poor gear change happened. Though it lacked a bit of feel and felt slightly num in its operation (This DMF clutch was replaced just befor our purchase, so it was as it should be). The one in the 206 HDi also feels the same, a little num compared to conventional clutches. The one with a solid flywheel has much more feel but can have a sudden change if your not careful. Though i much prefer the one without, not to mention its going to be reliable!

I really dont like DMF and dont see the point of them, cars never needed these before now and cars which have had a solid flywheel fitted after a DMF are no different in operation and there is certainly no vibrations, somehting which the DMF aims to prevent.

Infact we have had two cars which the DMF has had a slight vibration, so it can be even worse!

It seems to be a popular failing on modern cars now, which makes clutch replacement very expensive too. Transits are a nighmare if the DMF wheel fails, so im told.

I just hope these things die out quickly ....

My 2p worth! :lol:
Chris
07 Citroen C6 V6 HDi Exclusive - Red
07 Citroen C5 HDi VTR - Red
09 Citroen C3 1.4i VTR - Silver
01 Citroen Saxo 1.1i Forte - Mango Orange
.
93 Ford Mondeo 2.0i GLX
19 Hyundai i10
Sid_the_Squid
Posts: 590
Joined: 21 Apr 2009, 15:35
Location: Hemel Hempstead (unfortunately)
My Cars:
x 2

Post by Sid_the_Squid »

Feel better soon Vince :).
Expanding a bit on what Vince said about vibration absorption, not so long ago I did a wee bit of research into the DMF situation, so far dug up these useful links.

http://www.zf.com/corporate/en/products ... wheel.html
See the vid on the right under ’more details’.

A nice 3d animation, similar to the vid above.
http://www.youtube.com/watch?v=YnaXB8q3uzQ

I can see why manufactures fit them, judging by the extra expense they create I can see why people have them removed and replaced with conventional flywheels. The million £ question is; Are DMF's necessary in a modern car designed to be fitted with one?
Or to put it another way, does removing a DMF have any negative long term implications for your engine and drive train?

Very interested to hear your insights Vince, post back soon.
Gone to the dark side.

Past Citroens
'99 Xantia HDi Exclusive
'99 Xantia 3.0 V6 Exclusive (Green Goblin)
'02 C5 Hdi 110 LX Estate
'98 Xantia 1.8 sx auto with LPG
'00 Xantia Hdi (110) forte
'97 Xantia 1.9D sx
'93 Xantia 1.9D lx (my first) R.I.P
Citroenmad
Posts: 8125
Joined: 04 Dec 2008, 22:08
Location: Northeast
My Cars: 07 Citroen C6 V6 HDi Exclusive - Red
07 Citroen C5 HDi VTR - Red
09 Citroen C3 1.4i VTR - Silver
01 Citroen Saxo 1.1i Forte - Mango Orange
93 Ford Mondeo 2.0i GLX
19 Hyundai i10
x 110

Post by Citroenmad »

Sid_the_Squid wrote:The million £ question is; Are DMF's necessary in a modern car designed to be fitted with one?
Or to put it another way, does removing a DMF have any negative long term implications for your engine and drive train?
Well using my C5 as an example again, it was fitted with a solid flywheel at around 60K miles if i remember correctly. Its now done almost 118K miles and its been no trouble since it was fitted.

Only differences:
- Bite point slightly higher than DMF, but not really noticable
- Slighty sharper bite point compared to DMF

I cant see why either of those would be an issue, just feels like a conventional clutch, as you would expect.

There is certainly no vibrations which that video says the DMF stops, its just as smooth as the estate with a DMF.

So almost 60K miles on with a solid flywheel and no problems, cant see it causing any either. Where as if it had a DMF i might be getting ready for it to be changed again!

Apart from the expensive, its totally inconvenient to have a vehicle with a broken clutch. Xantia HDis dont have a DMF, but have the same engine as my C5, so its not going to cause any problems not having one fitted. Though it might be different for other makes of cars.
Chris
07 Citroen C6 V6 HDi Exclusive - Red
07 Citroen C5 HDi VTR - Red
09 Citroen C3 1.4i VTR - Silver
01 Citroen Saxo 1.1i Forte - Mango Orange
.
93 Ford Mondeo 2.0i GLX
19 Hyundai i10
wheeler
Posts: 6848
Joined: 21 Sep 2002, 19:07
Location: United Kingdom
My Cars:
x 717

Post by wheeler »

Citroenmad wrote:It seems to be a popular failing on modern cars now, which makes clutch replacement very expensive too. Transits are a nighmare if the DMF wheel fails, so im told.
Even Ford do a genuine solid replacement kit for the transit now. What does that say ?
User avatar
rabenson
Posts: 328
Joined: 15 Jul 2002, 15:14
Location: Northallerton, N Yorks. UK
My Cars:

Post by rabenson »

My understanding is that the main reason for a DMF is to allow the engine to drive in a higher gear at low RPM thus achieving better economy. I know that my C5 is much happier at 30 mph in 4th than my previous xsara hdi (solid flywheel) which didn't like going into 4th until at least 35 mph. I know that they aren't directly comparable but the C5 in general seems happier at low engine rpm thatn the xsara in all high gears.

Just a thought...

Ron
2007 C6 2,7 HDI exclusive 95k
2004 C5 VTR HDI 103k
User avatar
myglaren
Forum Admin Team
Posts: 25366
Joined: 02 Mar 2008, 13:30
Location: Washington
My Cars: Mazda 6
Ooops.
Previously:
2009 Honda Civic :(
C5, C5, Xantia, BX, GS, Visa.
R4, R11TXE, R14, R30TX
x 4889

Post by myglaren »

rabenson wrote:My understanding is that the main reason for a DMF is to allow the engine to drive in a higher gear at low RPM thus achieving better economy. I know that my C5 is much happier at 30 mph in 4th than my previous xsara hdi (solid flywheel) which didn't like going into 4th until at least 35 mph. I know that they aren't directly comparable but the C5 in general seems happier at low engine rpm thatn the xsara in all high gears.

Just a thought...

Ron
I would agree with that.
I had my DMF and clutch changed last year and opted for a new (Valeo) DMF and clutch, although slightly more expensive than a solid flywheel.
The reason being that there are unconfirmed reports that where the DMF has been replaced with a solid unit, gearboxes seem to be failing prematurely.
As said, unconfirmed but the DMF is a cheaper option than a new gearbox.
Citroenmad
Posts: 8125
Joined: 04 Dec 2008, 22:08
Location: Northeast
My Cars: 07 Citroen C6 V6 HDi Exclusive - Red
07 Citroen C5 HDi VTR - Red
09 Citroen C3 1.4i VTR - Silver
01 Citroen Saxo 1.1i Forte - Mango Orange
93 Ford Mondeo 2.0i GLX
19 Hyundai i10
x 110

Post by Citroenmad »

Cant see why it would do anything with the gearbox? The solid flywheel still has absorbing srpings in the clutch plate.

Ive not noticed a difference, my C5 pulls just as well in 4th at 30 than the one with the DMF. It doesnt struggle at 30mph in 4th gear either.
Chris
07 Citroen C6 V6 HDi Exclusive - Red
07 Citroen C5 HDi VTR - Red
09 Citroen C3 1.4i VTR - Silver
01 Citroen Saxo 1.1i Forte - Mango Orange
.
93 Ford Mondeo 2.0i GLX
19 Hyundai i10
User avatar
rabenson
Posts: 328
Joined: 15 Jul 2002, 15:14
Location: Northallerton, N Yorks. UK
My Cars:

Post by rabenson »

myglaren wrote: I had my DMF and clutch changed last year and opted for a new (Valeo) DMF and clutch, although slightly more expensive than a solid flywheel.
The reason being that there are unconfirmed reports that where the DMF has been replaced with a solid unit, gearboxes seem to be failing prematurely.
As said, unconfirmed but the DMF is a cheaper option than a new gearbox.
Yes, I think I'll do the same thing when mine comes up for renewal (ca't be long now, from what I've heard....)!
2007 C6 2,7 HDI exclusive 95k
2004 C5 VTR HDI 103k
User avatar
rabenson
Posts: 328
Joined: 15 Jul 2002, 15:14
Location: Northallerton, N Yorks. UK
My Cars:

Post by rabenson »

Citroenmad wrote:Cant see why it would do anything with the gearbox? The solid flywheel still has absorbing srpings in the clutch plate.

Ive not noticed a difference, my C5 pulls just as well in 4th at 30 than the one with the DMF. It doesnt struggle at 30mph in 4th gear either.
Fair point!

Hmm - I'm starting to fell like the indecisive guy in the pub off the fast show... :wink:
2007 C6 2,7 HDI exclusive 95k
2004 C5 VTR HDI 103k
vince
Posts: 1409
Joined: 22 May 2008, 22:29
Location: oldham
My Cars:
x 13

Post by vince »

Origional post now updated.....

If anyone has any particular questions i can always try to source an official answer through LUK.

I know of a friend of a friend whose mark 4 Golf ate its gearbox when the DMF failed, i have him the information when he bought the clutch, he decided to chance it.....it didnt work out.

That said....even LUK advise that you have your old DMF checked by a garage before changing it just becuase your clutch has worn out....they are designed to last longer than a clutch so unless they have experienced damage then they dont always need changing.....

Many garages i speak to however are still unclear on DMF technology and dont possess the correct tools to check them properly.
1993 Citroen xm 2.1td, silver/grey, bowling ball wheel trims, 210k and climbing...
Citroenmad
Posts: 8125
Joined: 04 Dec 2008, 22:08
Location: Northeast
My Cars: 07 Citroen C6 V6 HDi Exclusive - Red
07 Citroen C5 HDi VTR - Red
09 Citroen C3 1.4i VTR - Silver
01 Citroen Saxo 1.1i Forte - Mango Orange
93 Ford Mondeo 2.0i GLX
19 Hyundai i10
x 110

Post by Citroenmad »

Im possibly the most indecisive person there is :lol:

However, if manufacturers are starting to take them off their new cars, i wouldnt be fitting one to a used one ...
Chris
07 Citroen C6 V6 HDi Exclusive - Red
07 Citroen C5 HDi VTR - Red
09 Citroen C3 1.4i VTR - Silver
01 Citroen Saxo 1.1i Forte - Mango Orange
.
93 Ford Mondeo 2.0i GLX
19 Hyundai i10
vince
Posts: 1409
Joined: 22 May 2008, 22:29
Location: oldham
My Cars:
x 13

Post by vince »

Hi Chris, thats an interesting point that i have not heard of.....

I might drop them an email to ask them for more info on it? They did say that DMF's are the fastest growing sector of the transmission business so i cant see why if there was going to be a global shift away from them?

That said, perhaps another more cost effective technological solution has been found in the vehicle manufacturing process? I know some higher end vehicles are moving towards semi auto boxes....

I'll see what i can find out :wink:
1993 Citroen xm 2.1td, silver/grey, bowling ball wheel trims, 210k and climbing...
User avatar
myglaren
Forum Admin Team
Posts: 25366
Joined: 02 Mar 2008, 13:30
Location: Washington
My Cars: Mazda 6
Ooops.
Previously:
2009 Honda Civic :(
C5, C5, Xantia, BX, GS, Visa.
R4, R11TXE, R14, R30TX
x 4889

Post by myglaren »

George, the mechanic who replaced the clutch and DMF, kept the old ones for me to see. They were pretty well shot at 120,000 miles.
Clutch still worked OK but it wouldn't have lasted much longer.
Tons of slogger in the DMF.
Citroenmad
Posts: 8125
Joined: 04 Dec 2008, 22:08
Location: Northeast
My Cars: 07 Citroen C6 V6 HDi Exclusive - Red
07 Citroen C5 HDi VTR - Red
09 Citroen C3 1.4i VTR - Silver
01 Citroen Saxo 1.1i Forte - Mango Orange
93 Ford Mondeo 2.0i GLX
19 Hyundai i10
x 110

Post by Citroenmad »

vince wrote:Hi Chris, thats an interesting point that i have not heard of.....

I might drop them an email to ask them for more info on it? They did say that DMF's are the fastest growing sector of the transmission business so i cant see why if there was going to be a global shift away from them?

That said, perhaps another more cost effective technological solution has been found in the vehicle manufacturing process? I know some higher end vehicles are moving towards semi auto boxes....

I'll see what i can find out :wink:
I can only say ive heard that some new cars are now not being fitted with DMFs from word of mouth.

However i have heard of many DMF not failing and doing hundreds of thousands of miles. For example a mag i subscribe to runs a Golf GTi as their test project. Its original DMF lasted until 200K miles!

But for peace of mind and ease of ownership id rather cars didnt have them. I know there are some advantages but i cant see why a normal clutch wouldnt be just as good and more reliable. However we have owned many cars with them fitted and still have one car with a DMF. We have not had to replace any, though i consider myself to be very light on clutches and would never expect to have to replace one through wear alone. However my thinking is a DMF might need replacing at some point.

We had a Stilo for a short time, the clutch was becoming awful to use and needed replacing. The fiat specialist said it was the dual mass flywheel breaking up and wouldnt last much longer. Didnt really want the hassle with that so i moved it on quite quickly. The car had not even done 40K miles. Our Scenic DCi was developing a groan from the clutch when setting off on hills, the Renault dealer put this down to the DMF, never caused a problem other than the noise but that car had not even done 20K miles. Which i dont understand, they seem to break up regardless of mileage or use, or some last and last.

Ive heard a lot of roumers of clutch replacements costing expensive amounts. Does a dealer not charge around £1000 for a Mondeos clutch replacement? Indies will do this cheaper i bet but thats still expensive, especially given that these Mundaneos are getting on now, it could be the cost of a car just to have a clutch replaced. I know our Freelander had a receipt for a clutch replacement for £1200, wow, you can buy a C5 for that amount!

Your information is very interesting, though with my expereince on the C5 it proves a DMF is not needed. However i believe this engine was developed at first with a normal, conventional clutch, only when it was put into the more modern cars did it get the DMF. So this might explain why the C5 is fine without a DMF. I can confirm that it is a Valeo replacement solid flywheel setup in the C5.

If we cant even drive over a speed bump without going at a snails pace then how are these things going to last when towing heavy loads?

Still, its something which you hope you will never have to think about and it does give a better, softer gearchange. Certainly wouldnt put me off buying another car with one, but its nice to have the peace of mind that my C5 hasnt got one. One less thing to go wrong i say! :roll:

Are you in favour of DMFs? seem more hassle than they are worth in some ways. Though i can see why some modern cars/engines might need them, though this seems a bit like an in built potential problem waiting to fail.
Chris
07 Citroen C6 V6 HDi Exclusive - Red
07 Citroen C5 HDi VTR - Red
09 Citroen C3 1.4i VTR - Silver
01 Citroen Saxo 1.1i Forte - Mango Orange
.
93 Ford Mondeo 2.0i GLX
19 Hyundai i10
Post Reply