DMF - what's it like with a solid one?

[Kozy]

My Mondeo TDDI had a SMF conversion, I didn't have any issues with it, neither did the previous 3 owners of it.

Can't comment on what difference it makes, as I never tried one with a DMF, plus my example was touching 200k and generally felt a bit st to drive. There was no judder, vibration or anything else to note though.

Max Torque, where do you work? I've tried emailing you before but got no response.

[Mr2Mike]

MX7 said:

Yes, but I didn't mention the clutch! I meant the inherent judder that all diesel engines have,

So you definitely didn't mention clutch in your opening post?

MX7 said:

Personally I think they are great for people who can't drive. If you have reasonable clutch control, then a solid one is fine.

"Judder" is used when describing a clutch related issue that Max_Torque has explained. The fact that you mention clutch control and then judder means the majority of people would assume you are talking about clutch judder.

Since the NVH problems and stress on the transmission from torque ripple only occurs when the clutch is fully engaged, how does reasonable clutch control resolve the problem?

[eltax91]

Wife has a VAG TDi 100 in her A3. It had done about 130k miles when the DMF went. After a lot of research we plumped for the SMF conversion kit from valeo.

Car now on 143k and feels no different. It's not fked anything else up yet.

[bonesX]

eltax91 said:

Wife has a VAG TDi 100 in her A3. It had done about 130k miles when the DMF went. After a lot of research we plumped for the SMF conversion kit from valeo.

Car now on 143k and feels no different. It's not fked anything else up yet.

Hmmm... what difference to the DMF does it make between your A3 and a 'mildly mapped' 400Nm?

[MX7]

Mr2Mike said:

"Judder" is used when describing a clutch related issue that Max_Torque has explained. The fact that you mention clutch control and then judder means the majority of people would assume you are talking about clutch judder.

Then they are wrong, and I think that anyone with the most basic of comprehension skills would understand what I meant.

[underphil]

Surely depends on the application in question, I'd never consider putting a SMF on. A four cylinder turbo diesel, but swapped the 15kg DMF on my old GTV V6 for the 8kg SMF from the GTA and it was all the better for it

[MX7]

underphil said:

Surely depends on the application in question, I'd never consider putting a SMF on. A four cylinder turbo diesel, but swapped the 15kg DMF on my old GTV V6 for the 8kg SMF from the GTA and it was all the better for it

I agree, some cars are more suited than others, but I know of a Mondeo turbo diesel that's absolutely fine.

The videos posted earlier in this thread show the 4-pot SNF engines in a very bad light, but they are using lightened Helix SMFs, so are hardly typical of an SMF conversion.

[Mark34bn]

Do you guys reckon a SMF would be OK in a BMW straight 6? ECP are doing a conversion for £450
http://www.eurocarparts.com/ecp/c/BMW_3+Series_2.8...
My clutch is showing it's age and knowing my luck the DMF will be on it's way out!

[Mr2Mike]

MX7 said:

Then they are wrong, and I think that anyone with the most basic of comprehension skills would understand what I meant.

In which case please explain how "reasonable clutch control" can prevent the NVH problems that DMFs were designed to resolve?

[MX7]

Mr2Mike said:

In which case please explain how "reasonable clutch control" can prevent the NVH problems that DMFs were designed to resolve?

I thought I already had.

"It is a matter of clutch control. In my opinion the problem is that DMFs mask bad driving practices. I've been in taxis that have pulled away on tickover."

If the DMF acts a damper, and you remove it, why would you think that you would be able to drive in exactly the same way as before?

[underphil]

Mark34bn said:

Do you guys reckon a SMF would be OK in a BMW straight 6? ECP are doing a conversion for £450
http://www.eurocarparts.com/ecp/c/BMW_3+Series_2.8...
My clutch is showing it's age and knowing my luck the DMF will be on it's way out!

possibly, but not sure - part of the reason I went from the DMF to SMF, is that the SMF was an OEM part from another Alfa that used the stroked 3.2 engine from the GTA rather than the 3.0 in mine, so pretty much a guarantee of sucess

[Mr2Mike]

MX7 said:

I thought I already had.

"It is a matter of clutch control. In my opinion the problem is that DMFs mask bad driving practices. I've been in taxis that have pulled away on tickover."

If the DMF acts a damper, and you remove it, why would you think that you would be able to drive in exactly the same way as before?

And the point you keep missing (deliberately I suspect) is that the DMF is only useful with the clutch fully engaged i.e. the point at which torque ripple can be transmitted through to the rest of the drivetrain. No matter how carefully you let the clutch out you can't possibly prevent this happening, so suggesting that careful clutch control is an alternative solution is simply wrong.

[Dift]

You have a mild remap on a fabia and your considering getting a SMF?

I wouldn't bother. Wait till it starts to slip and put in an uprated Sachs clutch.

There are lots of people running hybrid turbos with an uprated DMF, I don't think a mild map on a fabia requires anything as drastic as a SMF.

I ran a Sachs clutch and DMF on my old Ibiza (it wasn't standard )

[MX7]

Mr2Mike said:

And the point you keep missing (deliberately I suspect) is that the DMF is only useful with the clutch fully engaged i.e. the point at which torque ripple can be transmitted through to the rest of the drivetrain. No matter how carefully you let the clutch out you can't possibly prevent this happening, so suggesting that careful clutch control is an alternative solution is simply wrong.

You need to increase the revs as you pull off. As Max_Torque said, "Modern engines that make very high BMEP at low engine speeds ask very taxing questions of drivetrain stiffness". The problem with DMFs is that they give the uninformed driver the impression that their car can move off on tickover, but in reality the DMF is working it's nuts off to provide a smooth ride.

Have you had any experience of a car that's had a SMF conversion?

[MGJohn]

Rover fitted DMFs to their 1.8 Petrol 75s. Overkill or what? I can understand why they are a nicer driving experience in compression ignition engines [ Diesels ] but in petrol ... surely no need.

Conventional clutches are fitted to the smaller Rover 45s and MG ZSs using that same 1.8 litre engine.

With my 2 litre Rover 620ti, which idles at an indicated 750 rpm, I can pull away in first gear without touching the throttle. Same with the 1.8 MG ZS. Yes, you require careful clutch control to avoid stalling the engine.

Here's a DMF I removed from a Rover 75 1.8 engine. It's massive and heavy :~



Removal demonstrated how much the mass would deflect compared to a conventional clutch and flywheel. About twice as much at a guesstimate :~





I'm convinced it's overkill in some cars. It will also disguise poor clutch control but, poor clutch control means accelerated wear.

[anonymous-user]

MGJohn said:

It will also disguise poor clutch control

I'm not sure how many more times i can say this without loosing the will to live, but DMF's have NOTHING to do with "clutch control" or "smooth pullaways" or anything at all like that.

[MGJohn]

Max_Torque said:

MGJohn said:

It will also disguise poor clutch control

I'm not sure how many more times i can say this without loosing the will to live, but DMF's have NOTHING to do with "clutch control" or "smooth pullaways" or anything at all like that.

Calm down, you'll blow a gasket. By the way, how many times, I'm not counting ...

[B'stard Child]

Max_Torque said:

I'm not sure how many more times i can say this without loosing the will to live, but DMF's have NOTHING to do with "clutch control" or "smooth pullaways" or anything at all like that.

Agreed - unless you make them dinner plate light it shoudl't make much difference at all

What you should do if you are replacing DMF with SMF is ensure you put some shock protection in the system (unless you are doing it for a track/race car)

DMF has some shock absorbancy due to it's design and is normally used with an unsprung friction plate

SMF has no shock absorbancy (obviously) and should normally be used with a sprung friction plate

So this is 16 kgs of DMF without the friction disc or pressure plate



This is the corresponding friction disc



Replaced with a lighweight SMF (weighing 4.5 kgs)



And a friction plate with some shock absorbancy

[MX7]

Max_Torque said:

I'm not sure how many more times i can say this without loosing the will to live, but DMF's have NOTHING to do with "clutch control" or "smooth pullaways" or anything at all like that.

Yet when I was looking into SMFs for a friend I frequently saw comments similar to the one below.

"I find that the car now needs a little more gas to move off/reverse smoothly. However, this is a bonus for me as I had a few lazy pupils who just wanted to use the clutch, despite me trying to convince them that they should get used to using the gas too as if they buy a petrol car, they'll never get it to move. Now I have the SMF, the car will judder unless you use a bit of gas, so it feels like it might be going to stall... they use the gas, all is fine and bad habits are gone!"

[B'stard Child]

MX7 said:

Max_Torque said:

I'm not sure how many more times i can say this without loosing the will to live, but DMF's have NOTHING to do with "clutch control" or "smooth pullaways" or anything at all like that.

Yet when I was looking into SMFs for a friend I frequently saw comments similar to the one below.

"I find that the car now needs a little more gas to move off/reverse smoothly. However, this is a bonus for me as I had a few lazy pupils who just wanted to use the clutch, despite me trying to convince them that they should get used to using the gas too as if they buy a petrol car, they'll never get it to move. Now I have the SMF, the car will judder unless you use a bit of gas, so it feels like it might be going to stall... they use the gas, all is fine and bad habits are gone!"

SMF's are normally lighter - that would give rise to the comments you've seen - lighter = less flywheel effect

IF the weight is identical then the result should be very similar - but if you are replacing a DMF then SMF is normally by consequence lighter