Increasing the life of a dual mass flywheel

[VeeFource]

So it's looking like the dmf on my new Ibiza FR might be starting to fail despite the car having only done a mere 30k. I've recently noticed a rattling sound with the clutch roughly in it's biting position when in neutral and especially when the car's still cold.

I only bought the car 2 months ago so luckily it's still got a month left on the warranty which should hopefully cover this, but it's still pretty shocking given the car's just over 3 years old and with such low mileage. I can't speak for how it's been driven up till 1000 miles ago but this has still got me wondering about my driving style and whether it's likely to happen again with the next one.

Having done some reading up it seems there are two things that help kill dmfs, one is high torque at low revs and the other is heat build up. Given my commute features lots of lovely traffic lights, this has got me pondering the following:

1. Is it better to pull off with higher revs to reduce reduce the vibration spikes seen by the dmf or lower revs to reduce heat build up from slipping the clutch less?

2. I sometimes save fuel by increasing my slowing down distance and going into neutral between my down changes from 3rd to 2nd etc. But this increases the amount of time the engine is idling which means of course it spends more time at lower revs. But then it's not loaded like it would be if I were driving normally, so which is worse?

3. Does blipping the engine on the down change cause dmf killing vibes or does it help given it reduces clutch heat build up?

There's really not a lot of point in going diesel if I'm going to have to get a new dmf every 2 effing years!

Thanks in advance :-)

Edited by VeeFource on Sunday 15th December 11:16

[VeeFource]

Mr GrimNasty said:

I've done a 100K without giving the DMF a single thought, it's been faultless, and I do every thing 'wrong'. Either yours was sub-standard from new, thrashed to death, or massively clocked. Whatever, it is just bad luck/unavoidable. Like any other random car problem, there is no reason why a replacement will need any special driving consideration or not last 100K+. Loads of petrol cars have DMFs these days (although they seem to lead an easier life).

What car have you got? They seem to fair better on less powerful diesels, though it's not like mine's a leon FR. This car has only had one lady owner (which I believe given all the shopping receipts I've discovered) but may well have been laboured at low revs. It hasn't been clocked which I can tell from the finish on the controls let alone the history. As you say, it may just be bad luck, but if I can make my own luck i'd be more optimistic

Edited by VeeFource on Sunday 15th December 11:33

[VeeFource]

motco said:

Many say that it's more economical to use the over-run to decelerate - and I see the logic. However consider this: if you drop into neutral to slow the car naturally you do it earlier than if you use a trailing throttle. Whilst this does mean fuel is being used at a tickover rate, it is also true to say that you have been on power longer if you use any form of braking albeit engine or friction. Do you use less driving fuel by dropping into neutral early and idling, or by driving longer and 'braking' more by engine retardation? It would need either more data than we have from the engine designers, or a series of trials under controlled conditions to gain the answer.

Bang on! The amount of fuel used to idle the engine is so little compared to maintaining a higher speed for longer. Cars with high enough mpg meters will show 999mpg when coasting at higher speeds. The rate of decelleration when coasting is also so low that you've normally only lost 5-10 mph over 200 yards so if you use the engine braking in addition to this (manually braking as little as possible) then you'll have saved more fuel overall.

Thanks for all the other posts guys, feeling a bit better about the new car as I love it in every other way. Any thoughts on rev matching though?

[VeeFource]

Condi said:

Anyway, what I dont get about these DMF's is that they are there to protect the engine/gearbox from shocks through the transmission. How come then they dont have them on tractors and plant gear? A 400hp, 12 litre, tractor will send massive shocks through the transmission when pulling hard, and yet they dont have a DMF? Okay, the whole unit is bigger, but proportionally not massive.

Have you ever used one of those gearboxes though? They're not exactly slick and a car equivalent would undoubtedly be a big heavy thing, so would probably get slated in the new car reviews

ohtari said:

That's probably your answer. Most "one lady owner" cars I've experienced have been treated with no mechanical sympathy or care.

I really don't know why it's still considered a selling point!

Quite right, it did put me off in some ways, but then at least I knew it was unlikely to have been chipped.

I doubt the ridiculous eco gear change indicator helped either. Anyone following that idiotic advice would be idiling in 6th in a 50 zone..

Edited by VeeFource on Sunday 15th December 13:05

[VeeFource]

dfen5 said:

Just my 5p worth but the warranty won't cover that DMF - or I'll be amazed if it does..

Why wouldn't it? It has occured to me they might try and say it's normal seeing as it still drives ok, but it's not a serviceable item and it's clearly not right from the noises it's making.

Disco You said:

Is is possible/ what are the consequences of fitting a normal flywheel to an engine that comes with one as standard? I'm talking about the fiat 1.9 Diesel engine as fitted to Vauxhalls and Saabs in particular.

It's not recommended unfortunately. It's partly there to protect the gearbox from high torque spikes generated by modern engines so you can ruin your box and sometimes end up with bad drivetrain rattles

Edited by VeeFource on Sunday 15th December 13:25

[VeeFource]

ohtari said:

Unfortunately a DMF is usually regarded as a "wear and tear" item, just the same as a clutch, brakes or tyres.

It will depend on the dealer though.

Best of luck!

I'm sure they'll probably try that argument and if the car were higher mileage it might be understandable, but certainly not at 30k. They're designed to last the design life of the car which is definitely over 100k and if you google dmf and warranty it brings up loads of cases where the dmf is covered. So I can't really see how they'll get around that but even if not for the warranty I'm sure they're liable under the sales of goods act given I only bought it two months ago.

Thanks, I may need it!

Edited by VeeFource on Sunday 15th December 14:12