Dual mass flywheel ?

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Sun 1 Jan 2006 17:26
Dual mass flywheel ? - robert
Can anyone explain exactly what a dual mass flywheel is please.

An ordinary flywheel is nice and easy to understand - so why exactly is a DMF needed and what advantages does it offer?

Thanks in anticipation.
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Sun 1 Jan 2006 17:43
Dual mass flywheel ? - bell boy
makes lots of money for the people that makes them?
gets cars/vans in for work more often?
keeps the economy buyuont?

helps with modern cars/vans transfer power to the gearbox more smoothly as it is a flywheel/ rubber donut/ another flywheel all glued together with horse glue and take up is smoother (alledgedly)
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Sun 1 Jan 2006 18:10
Dual mass flywheel ? - Xileno {P}
Used on a lot of modern diesels to smooth the power delivery out.
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Sun 1 Jan 2006 18:18
Dual mass flywheel ? - jc
And gasolines!!
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Sun 1 Jan 2006 18:46
Dual mass flywheel ? - Aprilia
Basic idea is two masses coupled by a spring - theoretically better at smoothing the impulses from each power stroke. This may be true (although I have never noticed great differences). The problem is that they tend to come apart (listen for the characteristic 'squeak' of a dodgy DMF when you turn the motor off).
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Mon 2 Jan 2006 09:02
Dual mass flywheel ? - jc
Do they still have springs in clutch plates to do this as well?
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Mon 2 Jan 2006 09:45
Dual mass flywheel ? - Frogeye
Hello Aprilia.
Your mention of the squeak when you turn off has got me worried. I have a Pug 406Hdi 110, which I believe has one of these. Around the time the alternator was replaced, at vast cost, there has been a very loud squeak on starting and stopping the engine. This was believed to be the auxilary belt tensioner but after reading your comment, I am not so sure. The car has done nearly 90k miles and been squeaking for the last 10k. Should I be worried??
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Mon 2 Jan 2006 10:53
Dual mass flywheel ? - Aprilia
Hello Aprilia.
Your mention of the squeak when you turn off has got
me worried. I have a Pug 406Hdi 110, which I believe
has one of these. Around the time the alternator was replaced,
at vast cost, there has been a very loud squeak on
starting and stopping the engine. This was believed to be the
auxilary belt tensioner but after reading your comment, I am not
so sure. The car has done nearly 90k miles and been
squeaking for the last 10k. Should I be worried??


DMF's 'on the way out' do make a squeak on starting/stopping the engine. Wihtout hearing yours its impossible to say what is squeaking. I would take the belt off and start/stop the engine to see if the squeak is still there. Pug HDi's are known for DMF failure & I think factors now sell the flywheels for about half the dealer price, also I have heard you can put a standard flywheel on - not sure if this is true though.
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Mon 2 Jan 2006 11:16
Dual mass flywheel ? - ric22
has my mazda 6 ts diesel got one of these my mates ford mondeo diesel had one and it fell apart and now just the parts for the repair are over 500 quid let alone the normal lets slap his backside labour costs
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Mon 2 Jan 2006 12:15
Dual mass flywheel ? - Screwloose
Frogeye

There's an over-run clutch built-into the pulley on an HDi's alternator; well known for squealing.

Where did this replacement alternator come from? Still under warranty?
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Mon 2 Jan 2006 12:54
Dual mass flywheel ? - Frogeye
Hello Screwloose.
I assume the pulley came with the new alternator and is not the original. It was fitted last May by a local independent garage. I believe it came from a factors and cost £221 +VAT for the part alone. I have just looked at the bill and noticed that they advised a squeal from the belt idler pully. Your idea of the clutch in the new alternator makes sense.
Thanks
John

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Mon 2 Jan 2006 15:23
Dual mass flywheel ? - Roly93
Can anyone explain exactly what a dual mass flywheel is please.
An ordinary flywheel is nice and easy to understand - so
why exactly is a DMF needed and what advantages does it
offer?

The idea of a DMF is to provide the weight and thus the inertia of a 'solid' flywheel while damping out vibration spikes from the engine, especially where a diesel engine is involved. Roughly speaking they are 2 flywheels with a rubber buffer sandwich affair between them. If modern diesel cars didn't have a DMF they would have great difficulty getting the driving experience as refined as it is now.
I believe the clutch assembly isn't really any different to the way it has always been, but a lot of manufacturers are recommending that the DMF is replaced when a clutch assy is replaced, at obviously great cost.
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Mon 2 Jan 2006 16:26
Dual mass flywheel ? - robert
Thanks all - makes sense now ............
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