C5 dual mass clutch v solid flywheel

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peterg
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C5 dual mass clutch v solid flywheel

Post by peterg »

Has anyone converted their clutch to a solid flywheel type? My dual mass flywheel has started knocking so it's time to replace it I guess.....I've so far found a clutch and dual mass flywheel for £261 but there are solid flywheel conversion kits for significantly less. I've seen people say that DMFs were introduced to provide some damping between engine and gearbox on modern diesel engines and my C5 HDI has been remapped to help with towing my race car.....but at the same time I am no boy racer and dont do traffic light grand prix. Is the DMF really critical? It is an old car now and not worth a huge amount of money.....at the same time I also don't want to destroy the gearbox in a week or 2!
Any advice appreciated. The conversion seems to be very straight forward if I do go for it.
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GiveMeABreak
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Re: C5 dual mass clutch v solid flywheel

Post by GiveMeABreak »

My advice is to replace it with the dual mass flywheel that it was intended to work with - especially as you have had it remapped! Yes, the idea is that with the extra power and torque of more modern diesel engines, a lot more stress is created and the DMF is designed to dampen the torsional stress created on the drive systems. All that stress has to go somewhere and I can't see how a solid flywheel can possibly dissipate / absorb those stresses.

You run the risk of damaging the drive systems over time which will be a lot more expensive to repair. Your choice of course.
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myglaren
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Re: C5 dual mass clutch v solid flywheel

Post by myglaren »

£261 for clutch and DMF sounds suspiciously cheap.
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white exec
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Re: C5 dual mass clutch v solid flywheel

Post by white exec »

myglaren wrote:
30 Dec 2019, 17:36
£261 for clutch and DMF sounds suspiciously cheap.
Agree with that.

SMF set-ups are also sprung, of course - in the friction plate. DMF friction plates are unsprung (solid).
I have one on our 2003 RAV4 D4D, and it has done 150,000km without issue, after two DMF failures.
It has restored proper clutch control, and made hill-starts (fwd and rev) routine.
The brand of the 4-part SMF kit was Blueprint.
I cannot make a recommendation for "modern" Citroen use, because I haven't done it.
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Re: C5 dual mass clutch v solid flywheel

Post by peterg »

myglaren wrote:
30 Dec 2019, 17:36
£261 for clutch and DMF sounds suspiciously cheap.
By scouring the net and looking at various offers there are quite a few places with them around this mark - the make is LUK which is a fairly main stream brand.

before this C5 the other car I had with a DMF set up was a VW Eos and it had to be replaced at 60k miles which I didn't think was great I have no problem with clutch control on the DMF set up but I do worry that they aren't very durable and expensive for what they are. I probably won't keep the C5 more than another year or 2 (at most) - but I also don't want a load of vibrations coming through the cabin and the gearbox destroying itself - however I can't imagine a DMF provides loads of damping....I always thought they were brought in for smoothness not damping.
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bobins
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Re: C5 dual mass clutch v solid flywheel

Post by bobins »

I have heard that reversing a trailer - especially uphill - can lead to the early demise of DMFs.
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Hell Razor5543
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Re: C5 dual mass clutch v solid flywheel

Post by Hell Razor5543 »

bobins wrote:
30 Dec 2019, 18:31
I have heard that reversing a trailer - especially uphill - can lead to the early demise of DMFs.
And if it is a braked trailer it will eat the DMF for breakfast, and want another for lunch and one for supper!
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Paul-R
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Re: C5 dual mass clutch v solid flywheel

Post by Paul-R »

white exec wrote:
30 Dec 2019, 17:47
SMF set-ups are also sprung, of course - in the friction plate.
I've not held one in my hand but photographs I've seen look like the springs are much longer than in conventional sprung SMF friction plates.
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white exec
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Re: C5 dual mass clutch v solid flywheel

Post by white exec »

The problem with DMFs is that the flywheel is in two halves (like two heavy discs slotted together), with up to 45deg rotation possible one half relative to the other. One side takes the drive from the crankshaft, the other side transmits it to an unsprung clutch friction plate.

The two DMF halves are linked by either rubber, or (more usually) one or more long springs. The idea is that engine vibrations, or shocks from roadway or drivetrain, are "absorbed" by the spring. In the main, this was felt to be a good idea (in the late '90s) to prevent the inherent harsh running of direct-injection diesels from sending their vibrations down the drivetrain. LUK and others promoted this heavily, and opened up the possibility of manufacturers reducing the weight of transmission components. At the time, few manufacturers actually did this, but it is possible that evolution has resulted in less heavy (i.e. sturdy) drivetrains.

There is a downside to the long springing in the DMF. When you ask the clutch to do some serious work - eg hill-start, reverse hill-start (Rev is a higher gear than 1st on many cars), or towing or trailer work, the torque involved simply winds up (compresses) the spring to near maximum, and as it releases its stored energy it makes decent clutch control more difficult. This gets worse with age, as any damping that was originally built into the DMF tends to disappear with age. Coupled with that, the long springs themselves deform (compress), and the DMF acquires "slop" (backlash). This produces even worse clutch control, and can result in serious driveline clonks, and accelerated wear - and often destruction - of the friction plate.

The manufacturers now class DMFs as 'consumable' service parts, and usually recommend that they are replaced at the same time as the clutch. In practice, the clutch friction plate may actually outlast the flywheel, but flywheel slop and break-up (the infamous "tinkling" noise) usually brings on rapid clutch plate wear.

DMFs in good working order do "absorb" driveline vibrations, but most of these actually stem from harsh-running DI diesel engines. Such problems used to be unknown - witness the quiet and smooth indirect-injection (IDI) Peugeot-Citroen XUD engines we all know and revere.

As we head towards an electric future, this sort of tomfoolery will surely vanish. There's a viewpoint I agree with that says the best (emissions aside, maybe) of modern diesels was probably the XUD era, and since then ICE engines have been increasingly hobbled by a whole gamut of three-letter tweaks, including EGR, DPF, and certainly DMF. A shame the final curtain will fall on a less-than-best performance.
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Paul-R
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Re: C5 dual mass clutch v solid flywheel

Post by Paul-R »

Paul-R wrote:
30 Dec 2019, 19:01
white exec wrote:
30 Dec 2019, 17:47
SMF set-ups are also sprung, of course - in the friction plate.
I've not held one in my hand but photographs I've seen look like the springs are much longer than in conventional sprung SMF friction plates.
Here's an example,

Image
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Paul-R
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Re: C5 dual mass clutch v solid flywheel

Post by Paul-R »

Valeo (an OEM supplier of clutches) seem very confidant that their SMF conversion kits are well up to the job. They specifically claim "full engine and gearbox protection".

https://www.valeoservice.co.uk/en-uk/ne ... -dmf-myths
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Re: C5 dual mass clutch v solid flywheel

Post by peterg »

I think I'm convinced to go solid! I take it the fitting does not require any more work than simply fitting a DMF kit?
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Michel
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Re: C5 dual mass clutch v solid flywheel

Post by Michel »

The last C5 I had (from Citroenmad Chris) was a 2.0HDi 8v which had been converted. I honestly couldn't tell the difference and it had 40,000 miles on that setup when I sold it to Rob also on here..
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white exec
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Re: C5 dual mass clutch v solid flywheel

Post by white exec »

Given the age of the car, and that Valeo themselves have produced an SMF kit, I would be going for it.
My inclination is to avoid LUK product.
I would have fitted a Valeo kit to the RAV4, but they didn't then produce them for any Toyota "for commercial reasons". Make of that what you will...
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Paul-R
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Re: C5 dual mass clutch v solid flywheel

Post by Paul-R »

white exec wrote:
31 Dec 2019, 09:52
... but they didn't then produce them for any Toyota "for commercial reasons".
Probably what I was just about to post a caution about.

I have read that Valeo don't produce SMF conversion kits for models where they are the OEM supplier of DMF clutches. I believe that it is something to do with not producing alternatives against the manufacturer's offerings.

In other words, you may not be able to source a Valeo SMF conversion kit and have to use another supplier's kit.