Dual mass flywheels - signs of failure?

Dual mass flywheels - signs of failure?

Author
Discussion

Mark34bn

Original Poster:

826 posts

142 months

Wednesday 12th January 2011
quotequote all
I'm on the verge of having my E36 328i clutch replaced and I've heard rumours about flywheel failure. Obviously I'd rather a £350 job didn't turn into an £800 job, but can you tell if a DMF is on the way out?
My car drives smoothly enough and TBH I can't hear anything abnormal.

Cheers
Mark

Max_Torque

16,551 posts

182 months

Wednesday 12th January 2011
quotequote all
If the DMF is REALLY creamcrackered, you can get them to hit the end stops (and get a nasty metalic knock you can hear in the car) if you tip in and out of the throttle aggressively in a high gear. Generally, whilst the clutch is off it's easy to check the DMF for excessive run-out(or cracked / fatigued spring pack) at the same time.

powerstroke

10,267 posts

125 months

Wednesday 12th January 2011
quotequote all
Sometimes you can feel vibration though the clutch pedal ....

stevieturbo

15,394 posts

212 months

Wednesday 12th January 2011
quotequote all
Although they are pretty much considered replacement items, despite their ridiculous price.

Why manufacturers insist on using these pieces of crap is beyond me

Max_Torque

16,551 posts

182 months

Wednesday 12th January 2011
quotequote all
stevieturbo said:
Why manufacturers insist on using these pieces of crap is beyond me
er, maybe because of the MASSIVE powertrain NVH benefits.............. ;-)

mk2 24v

552 posts

129 months

Wednesday 12th January 2011
quotequote all
Max_Torque said:
stevieturbo said:
Why manufacturers insist on using these pieces of crap is beyond me
er, maybe because of the MASSIVE powertrain NVH benefits.............. ;-)
really? my mates 1.8t golf had a dmf. thats been converted to a g60 normal flywheel and clutch assembly without any increase in noise transmission through the car biggrin

to the OP, can you not retro fit a non-DMF from an earlier bimmer?

Old Merc

2,803 posts

132 months

Wednesday 12th January 2011
quotequote all
GSF & EURO do flywheel/clutch kits to replace DMF jobs.I agree,why do they fit these expensive DMF?? !! I`ve spent my time with Peugeot`s,in the old days never replaced a flywheel in my life and clutches could last 80-100K.Now clutches & DMF are replaced in under 50K at £1000 a time.!!

Mark34bn

Original Poster:

826 posts

142 months

Wednesday 12th January 2011
quotequote all
Funny you should say that....
I've been looking at single mass flywheels. I mean if it needs replacing then man-logic suggests an upgrade could be on the cards.. BUT I'm worried about the downsides. My car is a road car and I don't want to hear chattering (or whatever it is)
I drove an early E36 320i years ago and I believe these had solid flywheels. That car was really nice and certainly didn't have refinement problems.
If anyone has been in an E36 with a solid flywheel I'd love to hear your opinions.

Max_Torque

16,551 posts

182 months

Wednesday 12th January 2011
quotequote all
mk2 24v said:
Max_Torque said:
stevieturbo said:
Why manufacturers insist on using these pieces of crap is beyond me
er, maybe because of the MASSIVE powertrain NVH benefits.............. ;-)
really? my mates 1.8t golf had a dmf. thats been converted to a g60 normal flywheel and clutch assembly without any increase in noise transmission through the car biggrin
No, you must be right, VW obviously fitted a DMF to that car originally just for fun..........


stevieturbo

15,394 posts

212 months

Wednesday 12th January 2011
quotequote all
Max_Torque said:
stevieturbo said:
Why manufacturers insist on using these pieces of crap is beyond me
er, maybe because of the MASSIVE powertrain NVH benefits.............. ;-)
Cant say Ive ever had an issue in any car Ive ever driven with a solid reliable flywheel.

So...what exactly are these benefits that cost a clean fortune every time a clutch is replaced, or even more often ?

Modern cars arent any smoother or quieter than some 15-20 year old cars.

Max_Torque

16,551 posts

182 months

Wednesday 12th January 2011
quotequote all
stevieturbo said:
Modern cars arent any smoother or quieter than some 15-20 year old cars.
you cannot be serious.....................



lets see, 2011 series vs 1991 5 series

or

2011 ford focus vs 1991 ford escort

or


2011 nissian micra vs 1991 nissian micra


or

2011 peugeot 207 vs 1991 peugeot 205

or, or, or, or


in fact, the only car i think of where this isn't true is a 2011 Caterham, vs a 1991 caterham, althought even then, with the current injected duratect it drives a lot smoother at low speed than the carb'd XE in the '91 car!!!

laugh

Pigeon

18,535 posts

211 months

Thursday 13th January 2011
quotequote all
I have seen innumerable posts on here from people who have replaced them with standard solid flywheels and not had a problem. So I don't buy the argument that they are necessary for NVH. I think that's just an excuse, and the actual reason is that they mean the manufacturers can make more money, firstly from selling replacements and secondly because the horrendous cost means the cars don't last so long on the second hand market and more people buy new ones.

stevieturbo

15,394 posts

212 months

Thursday 13th January 2011
quotequote all
Max_Torque said:
stevieturbo said:
Modern cars arent any smoother or quieter than some 15-20 year old cars.
you cannot be serious.....................



lets see, 2011 series vs 1991 5 series

or

2011 ford focus vs 1991 ford escort

or


2011 nissian micra vs 1991 nissian micra


or

2011 peugeot 207 vs 1991 peugeot 205

or, or, or, or


in fact, the only car i think of where this isn't true is a 2011 Caterham, vs a 1991 caterham, althought even then, with the current injected duratect it drives a lot smoother at low speed than the carb'd XE in the '91 car!!!

laugh
I'm very serious. Yopur comparison isnt valid. You are comparing a complete car. So are you saying if you fitted a DMF to a 1991 Escort, it would suddenly transform the car into a Rolls Royce ? Or same fitting a DMF into a 1991 Micra ?
No, so get real.

Do you really think that any of the drivers of those cars, which are at the lower end of the price scale care about a minute difference in smoothness, at some point when driving, compared to the hideous cost of having to replace a complete clutch and flywheel costing maybe 10% or more of the value of the car, usually at an incredibly low mileage ?

I'd imagine if you placed 2 cars side by side and let people drive them, identical cars albeit one with a DMF, an one with a normal flywheel. They wouldnt be able to tell the difference.
Which is probably why so many people DO replace them with solid flwyheels and drive away with no noticeable difference inside the car, other than peace of mind in their wallet.

Pumaracing

2,089 posts

172 months

Thursday 13th January 2011
quotequote all
stevieturbo said:
Although they are pretty much considered replacement items, despite their ridiculous price.

Why manufacturers insist on using these pieces of crap is beyond me
Seconded.

AcidReflux

3,010 posts

219 months

Thursday 13th January 2011
quotequote all
I thought DMFs were important for modern ultra-high-compression diesels, to smooth out the massive stop/start rotational forces imposed on the crankshaft by every compression-combustion stroke. I don't know why they're important on a petrol, where the compression ratio has a much lower limit and compression-cycle forces are lower.

Replacing a DMF with a traditional flywheel on a modern diesel would presumably shift those rotational vibrations and forces to other parts of the drivetrain.

Mr2Mike

20,143 posts

220 months

Thursday 13th January 2011
quotequote all
Pigeon said:
I have seen innumerable posts on here from people who have replaced them with standard solid flywheels and not had a problem. So I don't buy the argument that they are necessary for NVH. I think that's just an excuse, and the actual reason is that they mean the manufacturers can make more money, firstly from selling replacements and secondly because the horrendous cost means the cars don't last so long on the second hand market and more people buy new ones.
You honestly believe a manufacturer would install a component that is heavier, more complex and considerably expensive purely to build in obsolescence? There are much cheaper ways this could be done if their design goal was simply to give their cars a bad reputation.

Besides NVH issues, a DMF protects the drivetrain. With the amount of torque developed by modern common rail turbo diesels, the gearbox is already under a lot of stress, but the torsional vibration developed by high CR and high combustion pressures adds to this and can reach damaging levels. They also allow a given engine to idle at a lower RPM, giving fuel savings.

stevieturbo

15,394 posts

212 months

Thursday 13th January 2011
quotequote all
Mr2Mike said:
Pigeon said:
I have seen innumerable posts on here from people who have replaced them with standard solid flywheels and not had a problem. So I don't buy the argument that they are necessary for NVH. I think that's just an excuse, and the actual reason is that they mean the manufacturers can make more money, firstly from selling replacements and secondly because the horrendous cost means the cars don't last so long on the second hand market and more people buy new ones.
You honestly believe a manufacturer would install a component that is heavier, more complex and considerably expensive purely to build in obsolescence? There are much cheaper ways this could be done if their design goal was simply to give their cars a bad reputation.

Besides NVH issues, a DMF protects the drivetrain. With the amount of torque developed by modern common rail turbo diesels, the gearbox is already under a lot of stress, but the torsional vibration developed by high CR and high combustion pressures adds to this and can reach damaging levels. They also allow a given engine to idle at a lower RPM, giving fuel savings.
In short, it's cheaper to fit a DMF and have the customer pay for replacements, than it is to build a strong reliable transmission instead.

And as someone else said, the diesel argument doesnt hold weight, when they fit these flywheels to low powered petrol cars too.

oakdale

1,159 posts

167 months

Thursday 13th January 2011
quotequote all
The argument that these reduce stress on the transmission may apply when the flywheel is brand new, but as soon as they are just a bit worn, they must put more strain on the transmission with all the movement and rattling about.

I remember years ago when Ford were having trouble with these on Transits at quite low mileages, their official repair proceedure was to fit a solid flywheel.

The DMF flywheel is a piss poor idea to try and reduce vibration, but they don't last long enough to be of any use.

stevieturbo

15,394 posts

212 months

Thursday 13th January 2011
quotequote all
oakdale said:
The argument that these reduce stress on the transmission may apply when the flywheel is brand new, but as soon as they are just a bit worn, they must put more strain on the transmission with all the movement and rattling about.

I remember years ago when Ford were having trouble with these on Transits at quite low mileages, their official repair proceedure was to fit a solid flywheel.

The DMF flywheel is a piss poor idea to try and reduce vibration, but they don't last long enough to be of any use.
But as we know....all manufacturers care about, is them lasting long enough to get out of warranty !

Max_Torque

16,551 posts

182 months

Thursday 13th January 2011
quotequote all
Jeez, i love the "blinkers" on this site! It makes me laugh that people (genuinely,as far as i can tell) believe that a car manufacture would use the "lets make some money on parts sales" as a reason to use or not use any particular component when developing a new model!.


I have been developing powertrains for over 15 years now, and i have worked with every OEM in the game. The reason modern cars are so much better than say 20yo cars is that everybit of the car has been improved (it's called evolution). So no, just fitting a DMF to a 1990 5 series isn't going to make it into a 2011 5 series) BUT, each and every part is a little bit better, and when you add that up it makes a HUGE difference.

If you come on here and say "i have fitted a solid flywheel and there is no difference" what you really mean is "you can't tell the difference".

Well here's news for you, I CAN tell the difference.

Now, be my guest, go right ahead and swap out your DMF for a solid flywheel, it's your car afterall, and if you can't tell the difference, thats fine with me. BUT to suggest that the OEM (who most certainly can tell the difference) should stop fitting these devices because you don't think they work, well, that's rather different!!

Modern engines now have the ability to generate very high BMEP values at low rpm's (with accurate fuel and ignition control, higher CR's, varriable cam timing, varriable intale tuning etc etc) and to handle these higher BMEPs, powertrain stiffness is now an order of magnitude higher than any car built in 1990 (and i don't just mean revolving parts, think engine /trans / diff mounts, suspension bushes, dampers, bodyshell, everything!). if you couple a modern engine (be it petrol or diesel) to such a powertrain, at low rpm and high throttle openings (where you now need to run to make the fuel economy targets) the drivetrain NVH without a DMF is unacceptable. Hence, suprise suprise, just about all OEM's now fit DMF's as std to their cars.

If you can invent a better way of doing it, that costs less, and is more reliable than a DMF, then please, for God's sake, get it patented and sold to the oem's because you'd be a millionaire over night!!!!!


I use my car for towing my rally car, so it works pretty hard for its living. And at 105kmiles the clutch started to be a bit juddery, so i had the clutch changed as a preventative measure. While that was being done we found the DMF was just outside the runout tollerance. so i changed that too. It cost me over £400 to have a genuine BMW part fitted, but you know what, my now £130k mile car drives just like a new one. Now i could spend ages raving on the internet at how BMW deliberately built my car to fail, and how they are making such a huge amount of money out of selling me parts that i didn't need. But, you know what, i like my car (that's why i brought it) and it's lovely to drive, and i wanted to keep it that way. So, rather than cry like a baby, i "man'd up" paid the cost to fix it and moved on with my life ;-)