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.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.
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