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Dual Mass Flywheels - Your views?Views : 6701 Replies : 67Users Viewing This Thread : |
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Jul 16th, 2012, 14:34 | #1 |
Young Volvo driver
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Dual Mass Flywheels - Your views?
As someone who is relatively new to the inner workings of cars and have recently taking an interest thanks to my clutch symptoms, I wondered what some of the more experienced users have to say regarding DMFs (Dual mass flywheels)?
From what I gather this was a solution to a problem that didn't exist or didn't need fixed. From my own findings the benefits are as follows... To eliminate excessive transmission gear rattle, making driving comfortable at any speed, reduce gear change/shift effort, and increase fuel economy. From speaking with two different mechanics who have experience with both a single and dual mass flywheel, their own conclusion was that the DMF really doesn't offer much of a difference in the feel of the car when it's being driven. Of course that is just their opinion and I wanted to know other peoples views on this? My own car a 52 REG Volvo S40 1.8 petrol has a DMF and my worry is the pedal pulsation/judder/pedal weight changes is linked to a bad DMF. Also the failure of a DMF seems common in diesel motors. Anyway I'm new to all of this and would be interested to hear some of your thoughts
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Jul 16th, 2012, 14:46 | #2 |
Master Member
Last Online: Aug 2nd, 2018 19:03
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A pointless waste of money when it eventually goes wrong, which it will.
great idea by manufacturers, "Lets replace something which never breaks with something that will fail AND is expensive AND difficult to get out" Its bollocks about smoothness and easier gear changes anyway, anyone who cares about that buys an automatic and if you want better mpg stop fitting wide low profile tyres on the cars is what I reckon.
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Jul 16th, 2012, 14:47 | #3 |
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Whilst looking into the problems with my brothers audi 1.9 diesel engine it appears that they suffer with DMF's and most revert back to a solid.
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Jul 16th, 2012, 15:15 | #4 |
Brit in Germany
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A DMF is something, which will not really improve to much, other than comfort.
The problem being the following: A 4 cylinder engine doesn't run totally smooth. So it means a powerstroke doesn't straight away get followed by another one somewhere in the drive engine (a 6 cylinder does). So it will always be accelerating and decelerating. So, a car with 4 cylinders and a SMF will, if you leave it running at idle but in gear (all cars can do this), judder slightly, as the engine doesn't transfer a constant power to the gear box. In order to remove this (yes, people would complain about this, even in the old 700 and 900 series), the car and gearbox manufacturers came up with the DMF. This has enough "spring rate" inside to smoothen out the engine. The older 700 and 900 series had a little something behind the gearbox and infront of the prop - it is a little rubber disc with 6 screw holes. 3 for each side (prop and gear box). This acts as a damper between engine and drive wheels. It is constantly stretched and compressed whilst driving - no matter at what RPM. As a FWD car or rear engined car doesn't have enough space to fit some rubber dampers, the DMF was introduced. It reduces stress on the gearbox as well as drive shafts etc. and produces more comfort. So it isn't a "solution to a problem which doesn't exist". It is a solution to a problem to a long time issue which got more and more common as FWD and 4 (and 5) cylinder engines were getting more and more common.
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Jul 16th, 2012, 15:23 | #5 |
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I thought it was introduced thanks to modern diesels having such a choppy torque profile across the power stroke.
With the higher injection pressures and direct injection in modern diesels you get a great big power spike early in the expansion stroke, the DMF tries to smooth this out. Unfortunately adding more moving parts tends to make things less reliable.
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Jul 16th, 2012, 15:29 | #6 | |
Young Volvo driver
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Quote:
Such a good idea, shame about the execution.
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Jul 16th, 2012, 15:30 | #7 | |
Young Volvo driver
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Quote:
Interesting never knew that. Thanks for the informative post Daim
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Jul 16th, 2012, 15:32 | #8 | |
Young Volvo driver
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Quote:
This is not an option for every car as it seems some are designed around the DMF and it's not wise to convert back to a SMF.
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Jul 16th, 2012, 15:33 | #9 |
Rodney
Last Online: Aug 4th, 2016 05:02
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After reading up on DMF they appear to be for less noise vibration and harshness, better fuel consumption,for less stress on the gearbox/ transmission from high torque output engines.It appears they are more or less being seen in some instances as a 'consumable' like brake pads are..!!!
Apparently Ford and Mazda are looking at fitting some electronic trickery to limit torque output in first and second gear instead of using DMF. Thoroughly enjoyable research - off for a kip.... Regards |
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Jul 16th, 2012, 15:37 | #10 | |
Brit in Germany
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Quote:
Years ago you could get the over these DMFs by having clutch plate springs. But as the engines got more and more powerful (say 70 hp/liter of displacement instead of 30 hp like in the day), the forces got higher and the work on the clutch would simply kill it quicker than you think.
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clutch, dmf, dual mass flywheel, flywheel, smf |
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