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Old 4th November 2021, 00:07   #1
alanaslan
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Default To DMF or not to DMF on a M47R engine.

In another thread I stated that a DMF was not an essential part of the overall drive train in the M47R engine. I also stated that a solid flywheel was a suitable replacement.

If I understand the comments of my statements on this correctly. The reasoning for fitting a DMF flywheel is to protect the drive train.

When talking about the drivetrain are we referring to the big end bearings and crankshaft?
Are we talking about the shafts and bearings and gear train within the gear box?
Are we talking about the differential inner pod joints and external CV joints including the splines the torque is being sent through.

Remembering that the M47R engine has a BHP range of between 112 and 176. Making it the perfect candidate for a Front wheel drive motor car.

It is generally accepted that the maximum BHP where the advantages of front wheel drive begins to wane is somewhere between 180 and 190. Cars developing more than 190 BHP tend to handle better when the drive is through the rear wheels..

A Flywheel is a balanced disk of metal to ensure the smooth and constant rotational motion of a shaft that is being rotated by a series of impact forces.

A solid flywheel is a lump of metal bolted on to the end of the crank shaft the mass of the unit is measured Kg or grams and has a fixed external diameter thus creates a balanced and more constant rotational motion.

A dual mass flywheel is a fixed mass of material which is not mounted on a solid centre mount. The mount has a degree of flexibility. This flexibility allows the flywheel to smooth out the constant banging of the con rods on the crankshaft. This flexible mount also allows the outside diameter of the fly wheel to increase slightly as centrifugal forces increase.

With the above I think I have started the thread requested.

Alan


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Old 4th November 2021, 01:20   #2
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Just from my own personal thoughts and experience,

Dual mass flywheels were brought into to reduce vibration that is emitted from the crankshaft and and general running of the engine, this vibration especially on larger diesel engines, can sometimes be transmitted through the gearbox and in some cases the clutch pedal.

Car manufacturers I believe began fitting dmf's to reduce the likelihood of premature wear to components caused by vibration/torque and to perhaps gain a more refined and composed driving experience.

I'm guessing at this point but I do wonder if car manufacturers have considered the fact that many vehicles over the past 20 years.or.so are racking up more miles than they used to and one vehicle could go go through two or three or more clutches, each time the driver having little mechanical knowledge may continue to drive the car with the clutch slipping, steadily getting worse, damaging the flywheel, so.when the car goes into main dealer and find the tech finds the clutch is slipping, then advises the customer, and then the find the surface of the flywheel is badly damaged by the rivets of the friction plate coming into contact with flywheel, a new solid mass flywheel that could be out of balance with an engine that has already seen over 200k miles.. could cause a vibration issue due to being out of balance with the crank? As far as I'm aware when engine builders build an engine the crank and flywheel, pistons etc are all balanced as one? Or the flywheel and crank are.

A dmf, has springs to act as a damper and reduce any vibration, and because they all come with weights attached, I'm guessing that dmf manufacturers take into account the overall weight of the crankshaft so when the dmf is installed on any engine regardless, it shouldn't cause any undue additional vibration by being out of balance.

The above, I did have when I bought a 306 cabriolet years ago and some backstreet cowboys had fitted a clutch kit for the previous owners and to cut a long story short, transmech kits are to be avoided, the flywheel was badly scored and heated spotted and I had to source a new flywheel (only second hand available) and had to get a local engineering company to machine the surface of the flywheel and when fitted and everything was back in etc.. there was vibration from around 1200-1600rpm. Without any other obvious and less obvious causes, we could only put it down to the skimmed flywheel and the crank not being balanced together.

In terms of the m47r, afaik, all 75s with a manual gearbox came a dmf, to not have a dmf is unknown maybe risky? territory and to have one, is how it left the factory. My final thoughts are to just fit one, and a good quality one and if the clutch ever needs changing, check the flywheel surface, and the tolerance and spring resistance.
Just my thoughts

Last edited by biffa75; 4th November 2021 at 01:28..
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Old 4th November 2021, 06:15   #3
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I know a chap who fits clutches all the time for people who need a DMF but do not want to pay the price so opt for a non DMF kit. The clutch is very heavy and all generally fail within 10 months at most!
He warns them, they take no notice thinking they know better than the manufacturer and come back to him 6 months later with a knackered clutch asking why its failed. My clutch went on my ZT190 years ago and at 120 k miles. Andy on here fitted a new clutch and said the DMF was ok to use. All worked fine just a minor irritation was if I went up a very steep hill or up a high story car park I would smell clutch burning for a moment.
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Old 4th November 2021, 07:13   #4
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My thoughts are to always fit one. Manufacturers didn't go to the trouble of designing and making the DMF for no reason. Surely, if they thought it would be ok, and cheaper to fit a solid one then the project drive team would have done it.
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Old 4th November 2021, 08:11   #5
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Here is what one clutch manufacturer here says:

https://www.mbtautomotive.co.za/prod...lacement-kits/
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Old 4th November 2021, 08:19   #6
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Quote:
Originally Posted by kaiser View Post
Here is what one clutch manufacturer here says:

https://www.mbtautomotive.co.za/prod...lacement-kits/

i seem to be blocked by the site and need to log in

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Old 4th November 2021, 08:57   #7
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https://www.mbtautomotive.co.za/prod...lacement-kits/

here is the link again, I'll try to copy and paste:


The time has come and your vehicle is in the shop for a clutch replacement and the mechanic says your dual mass flywheel needs replacement. First of all it is recommended to replace the flywheel whenever replacing the clutch. This is even more important on vehicles with a dual mass flywheel, because they can fail and separate if overloaded which will damage the clutch. Additionally, dual mass flywheels are not skimmable and failure to skim a flywheel will result in premature clutch wear as well as shuddering and vibrations.

Our LMB Singlemass Flywheel Kits use Kevlar-Aramid compound clutches, when used in proper applications, can outlast other friction material clutches two to five times. Kevlar-Aramid provides the pulling capabilities of metallic button materials along with the smooth engagement properties of organic facing. This property of Kevlar-Aramid allows prolonged life of all drive train components as well as reduced downtime costs. In addition Kevlar-Aramid clutches can withstand more heat as well as increasing holding power over a typical clutch facing.

Converting from a dual mass flywheel to LMB Singlemass Flywheel Kit can be done on most vehicles if a kit is available.

The kits consist of a LMB flywheel, clutch disc, pressure plate and bearing. Most drivers will convert based on cost factors, while performance enthusiasts will convert to a single mass flywheel since it can handle increased engine torque and it gives direct feedback to the driver.

This, coupled with our class leading warranty, will leave you with peace of mind when you considering a clutch kit overhaul.

Please inquire with us if you are looking for a specific application.
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Old 4th November 2021, 09:23   #8
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Quote:
Originally Posted by Mike Trident View Post
My thoughts are to always fit one. Manufacturers didn't go to the trouble of designing and making the DMF for no reason. Surely, if they thought it would be ok, and cheaper to fit a solid one then the project drive team would have done it.
I would allow for individual choice and say that a person can omit the DMF if they so choose, in the same way that a person could choose to drive with a broken valve. However they should not recommend the practice to others unless tests have been carried out over a million+ miles on many cars in order to validate their decision as being robust.

I would always fit one and replace one with another DMF from the same manufacturer if the original was close to the manufacturer's specs or there was any doubt about its integrity e.g. worn bearing..

Quote:
Originally Posted by macafee2 View Post
i seem to be blocked by the site and need to log in

macafee2
Same here. I could not get into the site and having tried three times was blocked by login security!
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Old 4th November 2021, 10:07   #9
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Quote:
Originally Posted by MSS View Post
I would allow for individual choice and say that a person can omit the DMF if they so choose, in the same way that a person could choose to drive with a broken valve. However they should not recommend the practice to others unless tests have been carried out over a million+ miles on many cars in order to validate their decision as being robust.
This is clearly not a valid comparison and not even clever.
Fitting of standard classic clutches has been done to untold millions and millions of cars for about 100 years, and it has worked fine!
Driving with a broken valve is a fault, and cannot in any logical way be compared.
Don't try to make us out to be weak minded, if you don't agree. It is, still?? a free world, and a bit of thinking is never amiss.

And of course it is up to each to do what he sees fit.
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Old 4th November 2021, 10:14   #10
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Quote:
Originally Posted by kaiser View Post
https://www.mbtautomotive.co.za/prod...lacement-kits/

here is the link again, I'll try to copy and paste:


................First of all it is recommended to replace the flywheel whenever replacing the clutch. This is even more important on vehicles with a dual mass flywheel, because they can fail and separate if overloaded which will damage the clutch. Additionally, ..............


This, coupled with our class leading warranty, will leave you with peace of mind when you considering a clutch kit overhaul.

..........

The first paragraph copied above is complete rubbish. I have not seen car manufacturers or DMF manufacturers make such a recommendation. LUK - the manufacturers of DMF fitted to our cars - specify the tests to be undertaken in order to determine whether the DMF requires replacement.

With reference to the paragraph about 'class leading warranty' I wonder whether the warranty covers the loss of a car's refinement and lifetime longevity. Perhaps Kaiser can confirm?


Quote:
Originally Posted by kaiser View Post
.......

Most drivers will convert based on cost factors, while performance enthusiasts will convert to a single mass flywheel since it can handle increased engine torque and it gives direct feedback to the driver.
I would take the above to mean transmission of vibration and torque effects to the driver i.e. the feedback that most would wish to avoid in a reasonably refined car.


On my car I supplied a new clutch kit and a new DMF plus bolt set (in case needed) to trikey with the car at 151k miles and a heavy clutch. The DMF came back still in the boot with comment from Andy that it wasn't needed - the original was well within spec. The DMF are super reliable in our cars and not a way for the car manufacturers to brig additional work into their dealers' workshops as was stated in the original thread.

Last edited by MSS; 4th November 2021 at 11:56..
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