To DMF or not to DMF on a M47R engine.

[trikey]

I don’t get how fitting a Kevlar clutch can prolong the life of all drivetrain components?

[MSS]

Originally Posted by trikey

I don’t get how fitting a Kevlar clutch can prolong the life of all drivetrain components?

In the same way that removing the DMF does, surely!

I have to say though that if you could cut a display window in the bell housing, a Kevlar lined clutch would look the part!

[Jamiewelch]

Originally Posted by alanaslan

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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176bhp is only achievable when there is a larger turbo fitted too. And with a larger turbo you need to make sure it is VNT which provides smooth boost. If you fit a larger turbo that is just wastegate controlled there will be a huge surge when it comes on boost, that sudden surge in power will put strain on everything.

Having driven a car with a single mass flywheel, I wouldn't recommend it. There were so many vibrations coming from the engine, you could really feel the engine inside the cabin. With a DMF and good engine mounts you shouldn't really feel a thing.

It is all personal preference as to which flywheel to fit. My belief is that if you don't want to spend £300ish on a flywheel if it becomes faulty then you don't maintain cars properly. I know these cars aren't worth a fortune and spending £600-£700 on a clutch and flywheel fitted sounds a lot, but it would cost the same on any moderately modern car. It really annoys me when cars get scrapped because someone doesn't want to spend £400 on cambelts, or £450 on a replacement clutch. If you don't want to spend money on maintaining a car, don't buy a car.

Also remember these are nearly 20 year old cars for the youngest one. People can't expect everything to last forever.

[Mike Noc]

Originally Posted by kaiser

Here is what one clutch manufacturer here says:

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

Judging from the title of the post I think the OP wants a discussion on fitting solid flywheels specifically to the M47R engine. Given that they are pretty robust and you don't need to replace them every time you do the clutch I can't see the point of doing away with the DMF.

I did replace my DMF at around 411k miles because it was outside the wear limits. Luckily I had a very good used DMF from a scrapper I bought for the bonnet.

Another point with the M47R is that, unlike its M47 sister engine, it has a cast crank instead of a drop forged one. Now there is nothing wrong with cast cranks generally, but there have been a few reports of broken cranks on the M47R, and a solid flywheel will put more strain on the crankshaft.

So for that reason, and for the most refined ride for a stone crusher I'd stick with having a DMF, but each to their own.

[alanaslan]

Goodness what have I started?

The DMF was born in the early nineties to smooth out the vibrations from reciprocal engines that passed through the Kinetic energy store ie the flywheel. This was done to improve the driving experience.

The clutch should not be affected by the type of flywheel as the friction plate should either be engaged with the flywheel or disengage from the flywheel. Anything else is is clutch slip which generates heat and will damage the flywheel whither DMF or solid.

DMF units are very complex and in my first statement I simplified the way in which they work. However the job that they do was correctly described.

I will attempt to upload some diagrams and some referenced material for those technical minded people who understand the physics behind the kinetic store we call a flywheel.

On the post, I was asked to start this debate on the person whom asked me to start it, if I understood their statement said that a DMF should last the life of the car.
I feel that I should quote the AA spokesperson who when was asked directly how long a DMF unit should last? Her reply was four to five years.

I don’t know about other 75&ZT owners feel, but I am expecting the Spice tourer to last me another fifteen years at least. By which time she will be in her thirty’s. I will probably not be anything other than a box of ash by that time. I would hope that someone who cares will be looking after her.

I know that some people from Canfield university where I gave my lecture on DMF units have kept the main part of my presentation up to date with source references. I should have a copy of the referenced material. I will check my PC and see if I can upload the important parts along with their references.

Please everybody don’t fight about this, it was not my intention to pit member against member I was only trying to do as asked to. I am more than happy to share the physics and the maths behind the job carried out by a flywheel.


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[MSS]

Originally Posted by alanaslan

Goodness what have I started?

..............

Please everybody don’t fight about this, it was not my intention to pit member against member I was only trying to do as asked to. I am more than happy to share the physics and the maths behind the job carried out by a flywheel.


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What have you started? A bit of fun and exploring of ideas in some depth. I don't think it's a fight in any shape or form.

Please - let's see the physics.

The AA man must have been thinking of some particular model with early DMF failures - I believe the Ford Modeo was one such car in its mid-life model. But then Ford also had serious issues with the Powershift transmission.

On our cars I would be surprised if a DMF did not last 200k Miles and 10+ years unless abused or an isolated failure. Personally, I am one for replacing the DMF at 10 to 15 years of age if there are any significant signs of wear. A bill of say £300 for a new DMF over 10+ years or 200k miles is quite insignificant in terms of whole life costs of motoring.

[bl52krz]

I would say, go and fit a normal clutch without the DMF. Do not then come on here telling us that it is a load of rubbish and expect any sympathy. You will not get any.

[DMGRS]

I drove a ZT with a single-mass conversion - my observations were some 'chatter' from the gearbox, and a fair bit more cabin vibration.
I wouldn't do it personally, but with the DMF being quite expensive I can see why it's tempting. I'd happily have it on a less 'luxurious' car, but it did seem to ruin the 75 / ZT experience a little.

[MSS]

Originally Posted by trikey

I don’t get how fitting a Kevlar clutch can prolong the life of all drivetrain components?

The paragraph Kaiser posted has Competition Mods written all over it in my view. I've read such sites recommend removal of the DMF in order to achieve a better engine/drivetrain response but then go onto recommend replacement of driveshafts with carbon fibre units, due to the material's better ability to absorb vibration than metal, in order to reduce vibration. For say a rally or a track car, I can see that a DMF would be a liability as opposed to a benefit.

The important point is that the company referenced in post #5 is a mods manufacturer as opposed to a mainstream clutch manufacturer. I would tend to believe the writing on ZF/Sachs websites about DMF benefits.

In my view these sorts of debates are useful in that they inform newcomers that there are strong views on both sides of the debate. The individual can make their own mind up based on the debate.

For sake of completeness, here is the original post where this thread was requested.

https://www.the75andztclub.co.uk/for...9&postcount=19

[alanaslan]

I promise I will post the physics and maths as soon as I manage to get the desk top on to the form so I can cut and paste. I have never mastered the clever bits in the IPad, I am sure it can be done, but it is beyond me. Bring back DOS, Basic, Forth, and fortran, I could get my head around them in the eighties. But then I was in my forty’s. The common programs were WordPerfect, Lotus 123 and Paradox, All of which I could get to do what I wanted for some of the Paradox reports I had to use Twist and shout to landscape the reports. A lifetime ago.


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