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understanding flywheels smf dmf and planetary dmf

4043 Views 9 Replies 2 Participants Last post by  totalguy
after some research i have found some information on flywheels some of which is in video's

3D image of a dual mass flywheel

and an explanation of one type of dual mass flywheel

and here we have an explanation of smf dmf and planetery dmf

What is a Standard Flywheel

The flywheel is effectively a weight which is fastened to the end of the crankshaft of the engine. The power from the pistons tends to be created in "pulses" and the weight of the flywheel smoothes out these pulses by providing inertia to the rotating engine, (smoother on tick over), As well as providing a weight the flywheel has a gear around its circumference on which the starter motor operates and is a convenient means of attaching the clutch which provides a variable connection to the transmission. Taking your foot away from the clutch between gear changes makes the clutch last longer, hovering on the pedal is the single most cause of premature clutch wear.

Then what is Dual Mass flywheel

Modern diesel engines generate high torque and as a result they need extra smoothing out or "damping". To help with this process a DMF (Dual Mass Flywheel) is fitted. This is effectively two flywheels that transmit the drive through a number of springs which cushion the drive to the transmission 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 transmission. Along with their continued use in such applications, Dual Mass Flywheels are now also being fitted to high proportion of standard passenger vehicles (Cars MPV's etc) their primary purpose being to provide a vibration dampening action in the drive train at lower speeds.

The benefits of the Dual Mass Flywheel. ( the technical bit) To eliminate excessive transmission gear rattle, making driving comfortable at any speed, reduce gear change/shift effort, and Increased fuel economy. Mass Flywheel's 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 start-up and shutdown.

There are two basic types of Dual Mass Flywheel 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 petrol 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.

the above taken from a document here here http://www.aceautose...k/flywheel.html
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here we have a diagram of a dual mass flywheel im sure you dont need to see a single mass flywheel considering its straightforward.

Here pictured is a planetery dual mass flywheel

i couldnt find a video for explaining planetary flywheels but i found this video explaining about planetary gears.

and another one showing different ways planetary gears can work

obviously the planetary flywheel is the best option however everyone has their opinion on flywheels.

this thread i put together from several sources and should be used as a guide to flywheels. this is probably more related to diesels but it also relates to petrols too and i hope you find my research useful.

any additions to this thread would be good if anyone has anything to add.

would be good to make this a sticky i think
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Nice job TG, i agree the planetary dmf is gonna be a better option but how do prices compare to ordinary dmfs.

looking at
"Mass Flywheel's 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 start-up and shutdown."

It sounds like the dmfs are made for lower revs, so, will economical driving a little above tick over, say 1200-1400 be fine rather than what several people say about having to keep the revs above 1500?
well for mine (bit cheaper for other mk3 diesels) 200 for a luk one which is standard or a sachs one £330. you can however pick up a smf and full clutch kit for under 200 quid which is the main reason most will go for that.

im keeping mine so im considering a sachs.

i see what your saying about the rpm and my understanding of going for a planetary would mean..............

smoother at low rpm's thus you can keep it in gears at low rpm's without the car strugling thus giving you better ecconomy. unfortunately this would mostly benefit 6 speed owners especially on motorways at 70mph it would likely give 6 speed cars even better ecconomy than before. its been said a few times people get better ecconomy in 5th than 6th on 6 speed cars and from this research i can see why, as keeping it in fifth would give you higher rpm's and less vibration.

i also think with a planetary dmf it should make your engine quieter and make the clutch easier to use and smoother. its well known that these mk3 diesels can be stalled easy and you need to use your own methods to pull away where as most diesels you can lift the clutch quick and off you go.

i noticed a considerable difference with clutch useage comparing my mk2 to my mk3 that followed. the mk2 you could pull off easier and lift the clutch quicker especially so pulling off. me and many others no doubt have stalled their mk3 diesel at some point or other, some of us several times.

slightly off topic here but i find with aircon not quite 100% pulling away you have to slip the clutch a bit when the aircon is on, would be interesting to see the difference with a planetary dmf.

its a shame i couldnt find a planetary dmf video as that would be very interesting to see.
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I know the smf is cheaper and i know there are some who it has worked fine for but for others and myself is it worth taking the chance. If and or when mine goes ill be sticking with dmf, but the planetary one looks like it will be on my list even if it costs slightly more, i have seen a few sachs on ebay, two for about £290 and others for around £324ish.

With the lower revs i was thinking about driving at 30 mph. Mine is either about 1900revs in 3rd or 1300 in 4th give or take a bit, to get it to 1500 in 4th i am looking at doing a little over 35 which, considering the amount of speed cameras round here isnt worth taking the risk.

Regarding stalling easy, i have never noticed that with mine, when i get in and move off i can just lift the clutch without pressing the accelerator and it will go out the garage and up a gentle slope drive. When i then set off after closing the garage, yes i do have to give it a little rev to set it off the first time on the road but after that theres no problems. Its great when i get to traffic lights and hill starts, i can hold it on the clutch pedal just as im taking the handbrake off then give it some gas and off it goes. The trouble starts everytime i get in a petrol car i stall the buggers because i dont give them enough gas
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yes they will all pull off with no throttle and they will drive themselvees in 1st 5mph 2nd 10mph and about 18 in third. thats the anti stall feature.

the stalling happens usually when you use throttle to pull away but dont get it right an d keep the throttle too low it can stall.

i think the best option is planetary and im all for cheap but sometimes you are better paying more. yes a clutch kit dmf and starter is a big job and its not cheap either but you cant be tight when it comes to what you really want. sometimes you have to do what it takes to get what you will be happy with.

as an example i know a local guy 1.8 petrol with a dmf and he only changed the clutch! daft if you ask me but then its only a 1.8 petrol so it may be fine for that.

because modern diesels have a lot more bhp than they used to have and tons of torque even on our small engined mondeo's (comparing to the likes of v6 diesels) theres going to be vibration we see damaged caused by the vibration when the following parts fail

crankshaft pulley
aux belt tensioner
rear lower engine mount

to name the most common ones.

i think a planetary one would be best as it does a better job than a dmf, ive seen pictures of a dmf taken apart and the springs as pictured above on the dmf have been broken into several pieces so theyve been battered bad. i think the planetary dmf would spread the load more so it should last longer than a standard dmf.
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Sounds good, planetary it is, youll have to start a group buy offer

I agree sometimes its better to pay that bit more for quality and yes even if the parts arent knackered yet it seems sensible to change everything while the gearbox is off.

That bleeding anti stall thing scares the hell out of me sometimes, when i am slowing down i change down into third and suddenly the car starts going faster, definately a clenched moment
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lol i just dip the clutch for a bit till i shift down.
lol i just dip the clutch for a bit till i shift down.
OHHH naughty, dipping the clutch mean extra wear on the pressure plate thingys
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didnt know that. but then what about the box and engine if u dont do it? hmmmm
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