Mine has done 139k miles, still on the original clutch too.
It does seem though that clever control of injector timing (as per the new Fiesta) can reduce the need for a DMF.
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The more I think about the reasons for these things, the more I become convinced it's partly laziness in engine design and partly being able to give better performance figures because the overall mass of the flywheel is lower.
As an engineer, just looking at the thing, I know instinctively that it's wrong....not the way something should be. it may work, it may improve certain performance metrics (but at what cost), it may make up for other engineering shortcomings, but it doesn't make it right. I also hate unnecessary engineering complexity.
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As an engineer just looking at the thing I know instinctively that it's wrong....
Intriguing. Could you say more as to why? I can't see anything wrong with the idea, as such, just the way it seems to have been executed.
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I should have been clearer....of course the way it's executed and current designs I have seen don't look great. I am not even sure it would be economically possible to make a really good one.
The idea is a nice one make up for poor engineering and additionally lighten the flywheel assembly, whilst achieving a similar result to a high mass flywheel....but if that is poorly executed.....or costs so much to execute properly that it's a law of diminishing returns......then it's not worth making.
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125,000 on my 03 Passat with DMF and no problems, still on original clutch too.
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>>The idea is a nice one make up for poor engineering
No.
>>additionally lighten the flywheel assembly
No.
>>, whilst achieving a similar result to a high mass flywheel
No.
What branch of engineering do you work in?
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One thing I wondered; does the user manual for a DMF equipped car actually mention that there is a right way and a wrong way to operate the clutch in the vehicle?
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One thing I wondered; does the user manual for a DMF equipped car actually mention that there is a right way and a wrong way to operate the clutch in the vehicle?
Erm, there's a right way and a wrong way?
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SQ
Erm there's a right way and a wrong way?
Presumably, otherwise there wouldn't be so many 'I've been driving for years and years and never had a clutch problem before ' type posts on motoring forums.
Edited by Dynamic Dave on 28/09/2009 at 01:05
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What branch of engineering do you work in?
No
About as useful an answer as yours....why don't you enlighten us rather than just saying no?
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Its perhaps the opposite of telescopic forks on a motorbike, they are a bad idea that we are very good at making (ref BIKE current issue, article on hub centre steering) where as DMFs seem to be a very good idea that we are bad at making.
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Thing is, by and large they don't fail. I know plenty of people including myself who have run several DMF equipped vehicles to huge mileages without problems. The only reason they get such a bad press is that they are expensive to fix when they do go wrong. If it only cost £50 to fix one you'd never hear about it.
As for driving technique, no mysteries or black magic here either. As has always been the case, before or after the introduction of modern technology, if you want a car to last, treat it with respect. Don't strain the thing or jerk it around especially when the moving parts are cold, keep the vehicle properly maintained and by and large it won't let you down. ( Except Espaces that is....)
Short journeys where nothing gets up to temperature is what kills cars more than anything else.
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>>One thing I wondered; does the user manual for a DMF equipped car actually mention that there is a right way and a wrong way to operate the clutch in the vehicle? >>
Start and stop the engine with the clutch pedal depressed.
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Start and stop the engine with the clutch pedal depressed.
So all cars with DMF should also have 'stop start' fitted?
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As I mentioned in another thread regarding this topic, Mercedes has fitted Dual Mass Flywheels to all rear wheel drive cars whether petrol or diesel since the early 1980s. So they clearly can be made long lived.
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Start and stop the engine with the clutch pedal depressed.
>>
But that's common sense. Anyone who starts a manual car without their foot on the clutch is a moron.
Edited by David Horn on 27/09/2009 at 22:19
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>>Anyone who starts a manual car without their foot on the clutch is a moron.
Good grief. Heaven help anyone who does something really stupid when you're around!
As a thinking sort of moron, I don't bother making a point of this other than when it's very cold, or when starting the 30 year old Land Rover, which needs all the help it can get.
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Manatee - having seen someone very nearly get mashed between two cars when the driver accidentally started it in gear, I stand by my comment. Reducing the load on a cold engine is purely coincidental.
You cannot guarantee that a car is out of gear. The starter motor can easily overpower the handbrake in 1st or 2nd gear.
My brother's Megane (which had push-button start) used to insist that either the clutch or the brake pedal was firmly depressed before the engine would turn over.
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I'm with David Horn.
Moreover, why put unnecessary wear on an engine when you don't have to.
Unless of course you enjoy large, unnecessary repair bills.
Not very clever, is it?
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Depends on the car. Those of us brought up on vehicles with graphite clutch release bearings learned very rapidly that touching the clutch pedal at any time other than was strictly necessary in such was a short route to, er, "large, unnecessary repair bills". Therefore this is a horses for courses thing.
Also I'm not convinced as to the unnecessary wear aspect either. The flywheel and the majority of the clutch assembly still has to be rotated and I'm not sure that adding the gearbox input shaft and friction plate to this collection of weighty components makes any odds. If there were a significant difference here I'd expect to see automatics (where the T/C and transmission primary shaft are always coupled) blowing engines earlier than manuals, which doesn't appear to be the case.
The safety advantages cannot be discounted though.
Anyhow, back to the topic in hand. Looking at what a DMF does for you (ironing out the torque pulses from the engine) I'd have thought that the obvious, simpler and completely bulletproof answer to the problem would be a dual plane crankshaft as seen on the new Yamaha R1. Here the big end journals are in a cruciform arrangement as seen from one end of the crank rather than in a single plane so each decelerative compression stroke is exactly balanced by an accelerative combustion stroke and firing occurs at regular intervals (making your inline four pot feel suspiciously like a V4).
A fairly easy retrofit to an existing lump too. Fit dual plane crank, remap injection and ignition for two cylinders by 90 degrees. This would be a far better solution as it actually smoothes the torque delivery rather than "papering over the cracks".
A bonus is that with the smoother delivery of torque and power throughout the engine's rotation it should be possible to reduce the flywheel mass significantly too.
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>>firing occurs at regular intervals
It doesn't.
A four cylinder 2 stroke with a dual plane crank would have even firing intervals, but, not a four stroke. The R1 with a dual plane crank does not have even firing intervals.
It would make the problem worse.
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NC,
A conventional inline four has even firing intervals, each cylinder fires every 720 deg, there are four cylinders so a cylinder fires every 180 deg. 180 / 180 / 180 / 180.
A cross plane crank R1 fires at 270 / 180 / 90 / 180.
A four cylinder 2 stroke with a cross plane crank would also not have even firing intervals it would just fore twice as many times per revolution.
Edited by cheddar on 28/09/2009 at 17:37
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I think our wires have been crossed Cheddar. I hope this clarifies what I was trying to say.
An inline four cylinder four stroke with a conventional single plane crank has even firing, as you say, every 180 degrees.
An inline four cylinder four stroke with a dual plane crank does not have even firing.
An inline four cylinder two stroke with a dual plane crank generally does have even firing, every 90 degrees.
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Thanks for the clarification NC
An inline four cylinder two stroke with a dual plane crank generally does have even firing every 90 degrees.
It would have uneven firing:
2 cyls would fire together then another 90 deg later, another 90 deg later, then a 180 deg gap before the first 2 fire together again.
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>>2 cyls would fire together
Only if the apprentice under-draftsman's assistant laid out the crank! There's nothing to stop each crankpin being 90 degrees away from the nearest one - no need to have two firing together.
Edited by Number_Cruncher on 28/09/2009 at 17:52
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There's nothing to stop each crankpin being 90 degrees away from the nearest one - no need to have two firing together.
Then it would not be a cross plane crank, like wise a four stroke with 90 deg crank pins would have even firing intervals at 180 deg intervals.
Only if the apprentice under-draftsman's assistant laid out the crank! >>
As per the R1 270 / 180 / 90 / 180 four stroke (also the M1 MotoGP bike) the same principal was used on 500cc 2 stroke GP bikes.
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>>like wise a four stroke with 90 deg crank pins would have even firing intervals at 180 deg intervals.
No it wouldn't.
1 and 4 might mutually be 180 apart
2 and 3 might mutually be 180 apart
but there's no way of making, say 1 and 3 180 apart becasue the crankpin is now bent.
>>Then it would not be a cross plane crank
Erm,.... yes, it would.
>>As per the R1 270 / 180 / 90 / 180 four stroke
Yes, they're trying to achieve that non-even firing.
If they had laid the crank out like that in an attempt to get even firing, then, it would have been a lamentable failure.
Edited by Number_Cruncher on 28/09/2009 at 18:05
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1 and 4 might mutually be 180 apart 2 and 3 might mutually be 180 apart but there's no way of making say 1 and 3 180 apart becasue the crankpin is now bent.
I see what you mean NC re 90 deg crank pins.
A cross plane crank:
Cyl 4 fires, 270 deg later cyl 2 fires, 180 deg later cyl 3 fires, 90 deg later cyl 1 fires, 180 deg later cyl 4 fires again and so on.
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>>A cross plane crank:
Yes, there's probably some mix up with terminology too.
I'm taking cross plane, or dual plane to mean simply distinct from single plane crankshafts, I wasn't thinking of the exact layout of crankpins on the crank.
To wrap up, I would say that the at flywheel torque fluctuations from the firing strokes of modern diesel engines are much larger than they are from accelerating and decelerating the reciprocating masses, and using a cross plane (or whatever!) crank wouldn't be helpful.
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>>Not very clever, is it?
Scarcely moronic.
I wouldn't say anything to dissuade you and David from your belief that you are preserving your engines and keeping the world safe ;-)
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Humph B said "Short journeys where nothing gets up to temperature is what kills cars more than anything else. "
I disagree.
If you had added: " with normal maintenance".
I would agree. Most car handbooks tell you to change the oil and filter more frequently on short journeys. I bet few do,
Our Peugeot 106 diesel has an average journey length of 0.9miles. Owned from new, serviced annually and 17 years old and engine as new...
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To get back to the earlier points:
In Andrew English's review of the new Fiesta, which does not have a DMF, he implied that using the diesel's ability to trickle along at tickover was a contributory factor in DMF failure:
www.telegraph.co.uk/motoring/carreviews/2754322/Fo...l
Which cars have DMFs? See HJ's FAQ on this site
As an owner of a dmf equipped Golf 1.9Tdi, I've been watching the dmf saga: it seems to me that a combination of of driving insensitivity plus the susceptibility of certain engines to dmf problems leads to trouble.
JohnM
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Quote from Andrew English's Ford Fiesta road test:
I asked whether this would mean that owners would be encouraged to trickle their cars along at extremely low revs in traffic, which can be a source of premature dual-mass flywheel failure. Project manager Darren Palmer said that careful control of the pilot fuel injection together with sound insulation under the bonnet meant that noise and vibration were considered sufficiently reduced to delete the dual-mass flywheel. "We want to get rid of those things," he said. "They're expensive, heavy and they go wrong."
Sufficient evidence to claim repair costs if a Ford DMF fails?
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>>Sufficient evidence to claim repair costs if a Ford DMF fails?
No, I don't think so.
Expensive - yes, they must be more expensive than a solid metal disk, any manufacturer who wants to stay in business is always looking to be rid of expensive parts
Heavy - yes, for stress and thermal reasons, you can't make two small flywheels as light as one solid one
Go wrong - yes, any component which contains moving parts has the possibility of going wrong, DMFs can and do fail.
I don't think there's anything contentious or revelatory there which opens Ford up claims of repair costs.
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A Luddite take on this.
I had a Peugeot 205 diesel. It was a really excellent car spoiled only by its non-power steering and in that particualr example faultily assembled n/s rear brake. I crashed it quite hard into a screaming twit of a salesman on the A24 and had it repaired - good as new or damn nearly - by the insurance. It cruised quietly and comfortably at 80 or 90 and did 45-55 mpg driven like that. Eventually stolen, eheu!
No dmf, no turbo, parts you could get cheaper from a diesel specialist than a Peugeot dealer.
OK, all right, they have turbo by right and common rail now and very nice they are. But are they going to be so much worse with a good old iron flywheel? I can't help doubting it. I wish someone here would say what it's like having an aftermarket non-dmf (allegedly available for some Ford Mondeos).
No engine is perfect at all speeds anyway. If they seem to be - Rolls Royce, Lexus - it is at great cost. Dmfs sound like rubbish to me unless there's one that doesn't fail even when abused by clutch-slipping apes as all clutch assemblies are sooner or later.
To put it another way, NVH is part of motoring, unavoidable in the final analysis. I can live with that, so what's the matter with all these idiots in my way all over the roads? Hardly any of them could tell the difference.
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>>NVH is part of motoring
Yes!
It's a very important way that manufacturers try to make their cars better than the opposition. It's taken very seriously, and, in my opinion, rightly so.
With very few excetions, cars are extremely reliable, via tax regimes and expensive fuel, they are converging upon having good economy, via aerodynamics, their shapes and styles are converging. NVH is one area where manufacturers have a relatively free hand to innovate, within the limits of pass by noise legislation.
I can't see any sensible manufacturer beginning to ignore NVH.
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I can't see any sensible manufacturer beginning to ignore NVH.
Quite so. But the dmf may be a bit of a blind alley in the quest for that magic carpet feeling. Hats off to Ford if they are triyng to do away with the thing.
I quite like a car that sounds subdued most of the time, but I like to be able to hear what it's doing. I'm old-fashioned like that.
After all, your equanimity is going to be a bit shaken if the magic carpet suddenly makes some sort of vulgar noise. Better to hear the original slight change in tone really.
Edited by Lud on 29/09/2009 at 00:46
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Oddly, the seriousness with which NVH was being taken by some manufacturers was one thing that put me off going to work for a vehicle manufacturer.
I went to a seminar given as part of the institute of acoustics technical program, and was dismayed to listen to some engineers from a prominent luxury car maker waxing lyrical about how they were measuring and optimising door shut noise - how to make a satisfying thunk for the toffs to hear without making the door heavy or expensive.
To me, it represented a waste of resources, people, talent, time and effort, and I simply could not get excited about "sound quality engineering"
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a waste of resources, people, talent, time and effort, and I simply could not get excited about "sound quality engineering"
Not the important stuff, granted, but interesting in its way if people want to pay you for it I would think. For a while anyway. But no doubt you had another direction in mind.
Any decently original bit of engineeering makes its own noises including door clangs anyway.
I think what was putting you off was gigantist capitalism NC. I did some time on market research for the tobacco industry in the sixties. Tobacco advertising is pretty interesting for a while if people want to pay you for it. But the whole huge-scale committee-led enterprise is so damn dispiriting. No one sane can stand it for long.
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I asked whether this would mean that owners would be encouraged to trickle their cars along at extremely low revs in traffic which can be a source of premature dual-mass flywheel failure.
Why would this lead to failure? The Passat seems perfectly happy pootling along in 5th at 30mph and 900rpm. 65mpg too. :-)
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"Why would this lead to failure?" - due to the torque reversals the dmf has to absorb between tickover compression (diesel - high cr) and power stroke? (Must say that I've often used the VAG TDi ability to run on tickover - not so much now!)
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