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I am looking for ways to improve the life of the dual mass flywheel (DMF) in my 2005 Ford Focus tdci. I have heard that they can wear out quite quickly on the Ford Focus if they are driven in city conditions a lot, i.e. running on low revs and lots of stop-start driving.

Like a lot of people I spend 15 minutes sitting still in traffic most days, so I am trying to think of ways to improve my driving style to reduce the wear on the DMF.

  1. I understand that at low revs a diesel engine puts a lot of strain on the DMF because it is running less smooth, however is there much wear on the DMF when you are sitting idle in neutral in traffic? Surely there wouldnt be much strain on the engine, so not much strain on the DMF also?

  2. When you're running at low speeds in traffic and the revs are down around 1000rpm and the engine seems to be under strain and so could be straining the DMF, would it be better to drive faster at say 1500 rpm and then coast in neutral and then go back to 1500rpm when you're slowing down? Or to just stay driving consistently at 1000rpm?

I suppose it just goes to show that diesels aren't meant for city driving!

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up vote 7 down vote accepted

Reading around a bit on the dual mass clutch the friction plate between the two masses is the component that will often wear out as it is designed to keep from too much torque being sent through to the transmission, taking the hit itself instead (choice between burning up a couple hundred dollar flywheel or a transmission in the thousands of dollars).

Sitting idle in neutral, you are not putting the system under load and so that should not be creating wear.

Any time you press and then release the clutch pedal, you are disengaging the clutch disc from the flywheel and then re-engaging it. This causes wear on the clutch disc and flywheel.

The time you are going to put the most strain on the friction plate is during acceleration (that is when the most force is exerted onto the drivetrain) so I would suggest keeping a steady speed over speeding up, coasting, speeding up, coasting.

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I'll try my best to lengthen the life of the DMF by driving as you mentioned and maybe avoiding traffic. Oren Mazors solution to use a single mass flywheel sounds good, but would probably not be a safe solution for the transmission for most cars? – snowstreams Jul 25 '11 at 10:23
    
Many people tuning VW diesel engines woudl find their DMF failed between 5k and 20k after a remap. They would typically fit a "single mass" V6 flywheel. Many cars then 20k to 40k later needed gearbox rebuilds. – Steve Matthews 3 hours ago

Dual mass flywheels are susceptible to high energy loads, heavy acceleration and deceleration , towing does not help either, smooth driving and avoid towing where possible , this driving style will add considerably to life of the dual mass.

The real reason for dual mass is simply to add additional revenue to manufacturer supported workshops, since the introduction, gearboxes have become lighter, with lighter components such as synchromesh hub assembly's and more important carrier bearings, gearboxes are now manufactured significantly weaker taking advantage of the torque and vibration damping effects of dual mass flywheels .

It IS POSSIBLE WITH SOME VEHICLES TO SWAP OUT THE DUAL MASS FOR A SINGLE FIXED MASS FLYWHEEL.

It depends on the gearbox strength in the main. Audi, VW, Nissan ,Volvo, BMW, Land Rover Alfa Romeo and maybe some others have strong gearboxes and are fine with single mass conversions. Vauxhall, Renault Peugeot Ford and perhaps others are not well made gearboxes and can suffer problems running single mass flywheels. Some dual mass flywheels can cost up to £1000 on their own, outrageous really. The biggest manufacturer of dual mass flywheels are LUK and are fitted to many new vehicles as original equipment. LUK advertise 5 year warranty on replacement dual mass flywheels yet they are fitted to many new vehicles which only have 3 year warranties, work that out!. Forgot to mention starting the vehicle is a big issue to dual mass flywheels under cranking as a engine is all out of balance until it starts, avoid laboring the engine at low idle speeds trying to save fuel as that,s a big no no too, if you have a stop start vehicle turn it off, it will cause substantial wear to not only the dual mass but also the battery,the starter motor and the alternator and gearbox first motion shaft bearings on manual gearboxes.

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Bio Mass Flywheels absorb the harmonic torsional vibration caused by low rpm in few cylinder engines ie 4 cyl at under 1500 rpm, worst under load. That is when the bio will be working and wearing most and at a time that you can reduce wear, but low rpm is where the economy is and this is why the bio is used, to take advantage of the low rpm economy without the shudder or chatter (petrol motors have the harmonic vibration also) most v8s are smooth right from the idle petrol or diesel it is the length of the crank coupled to the amount of cyls.

Nailing it at the lights and walking off the clutch has to work it hard, also burnouts with axle tramp, I think would top the list for life reduction in the bio.

Best mileage from the BMF will be achieved while in top gear cruising over 1500rpm. If you are in town, you are in town, maybe use 1 gear lower and less peddle at low rpm being the only thing I can suggest, it may be better for you to consider auto. These diesels are good, add up the $ in fuel saving for 1 year.

I have a pig 307 with the 6sp, I run start it regularly, I have done 200k+ and the bio is buggered (clangs at the idle and shudders during take of) but I am still driving. I have towed with it and it is good towing. I am told? that the starter drives to the trany end of the bio, if so starting alone will work the bio.

LuK have a good article on bios BMF or DMF same thing. youtube. LuK Dual-Mass Flywheel - design and function. https://www.youtube.com/watch?v=gZpTQW21_yc

On torsional vibration have a look at this and imagine it to be your crankshaft. youtube. Torsional Vibration https://www.youtube.com/watch?v=FH4i360esn8

Also I watched a good article on fluid harmonic balancers (HB), same deal but at the front of the crank.

The effect is like an impact wrench driving your car, the vibrational torque peaks are high and are hard on the trany and the crank. Smoothing this is the job of the DMF and HB. In a non DMF 4 cyl vehicle, you will know when these forces are active as the vibration comes through the whole vehicle even a 6cyl truck, but I have used vehicles for long durations while under severe torsional vibration and have never had a broken crank or trany as a result, it was the shudder that is most irritating and what often forces one to down change a gear.

I say "she'll be right" and "don't you worry about that" well too much anyway.

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Bio mass flywheel? What is this, a flywheel made of plants? – I have no idea what I'm doing 7 hours ago

I can't offer you an opportunity to improve your DMF's lifecycle, but to be honest, do you want to? I had a 2003 tdi jetta that had one, and replacing it with a single mass flywheel improved performance quite a bit (and reduced the noise from the work out DMF).

it's also expensive to replace, so if you have to, don't get a new DMF.

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Getting a normal single mass flywheel sounds like a good idea, but as ManiacZX says below, the single mass flywheel mightn't be good enough to reduce the strain on the transmission and hence cause damage to the more costly transmission. I suppose it does all depend on the make and age of the car too. – snowstreams Jul 25 '11 at 10:02
    
I did it on a 2002 tdi, and over the course of 4 years have had zero problems. In my opinion (having only owned 4 different standard cars), for the average person's average driving style, you'll be fine. – Oren Mazor Jul 25 '11 at 15:53
    
Thanks, I might give that a try when ever the DMF does fail. I dont drive the car very hard so it could should out as a reasonable option. – snowstreams Jul 26 '11 at 11:14
    
@OrenMazor On my 2001 1.8t Jetta, I replaced my Dual Mass 1.8T flywheel with a Single Mass VR6 flywheel. It was 1/4 of the price, but introduced a little bit of chatter due to the unbalanced mass.. but should also be able to handle more, since it's for a VR6. Going on 40,000 miles now (last clutch lasted 176k), and it's fine. – Lynn Crumbling Dec 6 '13 at 6:29
    
I'm aware of several Volkswagen TDI's which have been equipped with single mass conversions and subsequently suffered gearbox failure. – Steve Matthews Apr 7 at 10:56

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