Dual Mass Flywheels - Your views?

[Volvo2002]

Originally Posted by LJD

If i changed anyones good condition DMF tonight without you knowing . And left you with a single mass , you would know in seconds

I likely would yes

[Daim]

Originally Posted by coughlanc

When it breaks weld, it skim it and balance it. FIXED !

Yeah, and then destroy the gearbox. Gearboxes will cope with the back and forth of the torque peaks but remember: the mechanicals don't care. They can be thrown back and forth. What does care, is the customer or owner driving a car constantly juddering. People complain about a slightly out of balance wheel effecting the comfort. They complain about a ticking noise of the engine. Don't you think they would then complain about the engine not powering the car smoothly? I would! Years ago (RWD) it only worked because there was enough rubber in the drive train!

Originally Posted by coughlanc

DMF = expensive bill when they fail. Most cars they're fitted in to don't produce torque spikes that would do any damage to a well made g'box.

Many car manufacturers offer a SMF options. Same engine, g'boxes. Last just as long.

First time I have ever heard of a company offering DMF AND SMF with the same boxes... Like said, a first time and I've had a lot of price lists and options in my hands... Volvo doesn't even make SMF anymore!

[Chris_C]

Not being someone who believes in modern cars... I'm not sure the industry is approaching this in the right way and maybe a different tack is needed.

DMF's, if I am to go from the previous posts in this forum, are to help out balance the unbalancedness (?! ) of 4 pots and of diseasals.

So.... rather than invent a better flywheel to try and redress the problem, we should be investing in removing the problem all together and in perfectly balanced engines (straight 6's or V12's I believe with the correct crank pattern are near perfectly in balance) and using petrol rather than diseasal?

Wooohoo, problem fixed!

[Shadeyman]

Originally Posted by Chris_C

Not being someone who believes in modern cars... I'm not sure the industry is approaching this in the right way and maybe a different tack is needed.

DMF's, if I am to go from the previous posts in this forum, are to help out balance the unbalancedness (?! ) of 4 pots and of diseasals.

So.... rather than invent a better flywheel to try and redress the problem, we should be investing in removing the problem all together and in perfectly balanced engines (straight 6's or V12's I believe with the correct crank pattern are near perfectly in balance) and using petrol rather than diseasal?

Wooohoo, problem fixed!

Did you not read these two posts?

Originally Posted by popuptoaster

I'd rather go back to an internal balance shaft in the engine and a normal flywheel, both of which normally last the life of the engine..

Originally Posted by Daim

Only thing is, internal balace shafts DON'T interfere with the torque peaks. They just counterbalance the engine movements but not the torque... So that wouldn't work what so ever... A 2.3l Ford Duratec has an internal balance shaft. The engine though still has a DMF.

The DMF has nothing to do with the balance of engine parts.

[y2blade]

Originally Posted by owyn

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.

Yep.

[Steve940estate]

Just read the bitabout welding the flywheel up and while it's a bit of a bodge it would work and not cost the earth.
You would need to fit a clutch plate with springs in it to take the shock load when the clutch is engaged.

From what I understand the dual mass flywheel not only stops this shock and prevents any torsional vibration from the engine from being trasmitted to the clutch and gearbox it also works the other way. I noticed when towing I got a bit more driveline shunt when the trailer was pushing the car, there was even less when the car was auto.

[Daim]

*edited*

[Chris_C]

Originally Posted by Shadeyman

Did you not read these two posts?

Maybe misunderstood them, I'm now confusing myself thinking about it.

Originally Posted by Shadeyman

The DMF has nothing to do with the balance of engine parts.

Ok, having thought more about it, I am missing the point. Apologies!