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Dual Mass Flywheel

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Kestrel View Drop Down

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    Posted: 01 Apr 2012 at 9:16pm
I have read lots of comments in the motoring sections of various weekend newspapers about diesel engines which have Dual Mass Flywheels - although I don't know what these are. According to some reports, these can fail after a certain mileage and can cost an arm and a leg to have replaced. I have just bought a 59 plate Acenta 2l dci. Does this model have a Dual Mass Flywheel, and if so, is it likely to fail; at what mileage; and how much might it cost to replace?
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Fee View Drop Down
Mary Whitehouse

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fee Quote  Post ReplyReply Direct Link To This Post Posted: 01 Apr 2012 at 9:19pm
Taken from the web... not my fab knowledge!!!!!

In modern light-diesel technology we are seeing much greater horsepower and torque gains sometimes coupled to better fuel economy. Dual Mass Flywheels have been used in many light-duty diesel trucks since 1987 that are fitted with a standard manual transmissions . Along with their continued use in such applications, DMFs are now also being fitted to high performance vehicles such as BMW’s and other similar luxury vehicles their primary purpose being to provide a vibration dampening action in the drive train.


The benefits of Dual Mass Flywheels

To eliminate excessive transmission gear rattle, making driving comfortable at any speed,
reduce gear change/shift effort, and
increase fuel economy.
Why is a Dual Mass Flywheel needed?

Transmissions in light duty trucks diesel powered vehicles have a by default a heightened sensitivity to fluctuating torsional inputs. This results in a strong torsional resonance or vibration that occurs during operation of the vehicle within normal driving ranges.

By providing a vibration dampening action that is superior to the normal dampening actions in a normal clutch arrangement the vehicle can be operated for longer periods without long term damage.

The dual mass flywheel construction relocates the damper from the driven disc to the engine flywheel. This repositioning dampens engine torsional vibrations more than is possible with standard clutch disc dampening technology.


Function and Operation

The function of the Dual Mass Flywheels or DMF is to isolate torsion crankshaft spikes created by diesel engines with high compression ratios. By eliminating the torsion spikes, the system eliminates any potential damage to the transmission gear teeth. If the DMF was not used the torsional frequencies could damage to the transmission.

DMFs are designed to provide maximum isolation of the frequency below the engine’s operating RPM, usually between 200-400 RPM. The time that the DMF works hardest is during engine startup and shutdown.



There are two basic types of DMF The first type of dual mass flywheel, or DMF as it is more commonly known, is made up of a primary and secondary flywheel with a series of torsion springs and cushions.

There is a friction ring located between the inner and outer flywheel that allows the inner and outer flywheel to slip.

This feature is designed to alleviate any damage to the transmission when torque loads exceed the vehicle rating of the transmission. The friction ring is the weak spot in the system and can wear out if excessive engine torque loads are applied through it.

The system also has a center support bearing that carries the load between the inner and outer flywheel.

The system is also fitted with damper springs to absorb shocks.

The second is designed with planetary gearing (planetary DMF) is designed especially for engines with stronger vibrations in the lower rpm range. Although these are primarily diesel engines, this type of DMF provides a smooth engine output comparable to that of gasoline engines.

This type provides in addition to greater driving and shifting comfort, benefits for drivers include lower fuel consumption because the idling rpm is lower.


Edited by Fee - 01 Apr 2012 at 9:21pm
2.0 Visia 2007, 1.5 Dci Acenta 2008' 1.6 Acenta 2009 and 1.5dci N-Tec 2011....bye bye Qashqai!! hiya Juke 1.5dci NTEC
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Len Ash View Drop Down

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Len Ash Quote  Post ReplyReply Direct Link To This Post Posted: 01 Apr 2012 at 9:36pm
All modern diesels have a DMF.

Forget horror stories, failure used to occur on a few early applications and then only after starship mileages or hideous abuse. And taxis.
2012 1.6 DCi S/S Tekna in White
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2Fat2Bald View Drop Down

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Post Options Post Options   Thanks (0) Thanks(0)   Quote 2Fat2Bald Quote  Post ReplyReply Direct Link To This Post Posted: 01 Apr 2012 at 10:46pm
Anything *can* fail, at any time.

DMFs have proven to be a minimal failure risk when designed properly, maintained properly and treated with at least a modicum of respect. There may be a few designs out there that aren't as reliable as they should be, but the Qashqai isn't known to be one of them. Given how many have been sold to date I think someone would have noticed by now if there was.

I wouldn't worry. I remember as a kid people saying not to go for these newfangled overhead cam engines. Then it was not to go for this complex EFI nonsense. Then avoiding catalytic converters... etc etc...

Edited by 2Fat2Bald - 01 Apr 2012 at 10:48pm
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n-tec FLASH View Drop Down

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Post Options Post Options   Thanks (0) Thanks(0)   Quote n-tec FLASH Quote  Post ReplyReply Direct Link To This Post Posted: 02 Apr 2012 at 6:02am
i had a 2.0ltr tdci ford mondeo mk3 54 plate with 64k 2yrs old at time my DM flywheel went you can tell when its on its way out cos of the starter motor sticks and then fails to start the car, cost was £200 for Dual Mass flywheel but while it was out also got garage to fit new clutch £120 at same time its the labour that adds it up think all in was £900 that was from local garage main dealer would have been £2.500,hoping QQ does not have Dual Mass wheel (but it looks like it does)



Edited by n-tec FLASH - 02 Apr 2012 at 6:13am
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