What is the Difference between single mass and dual mass flywheels?

[Mertyvw]

Any advice on what is what and which is better.? thanx

[berg]

You need a response from someone more technical, but the "dual mass" was described to me as a "rubber doughnut" which stops noise, vibration etc. Many tuners have said that the DMF construction is at its limit at about 300bhp so if you have a KO4 and are going stage 2+ you need to swap to a SMF, the advantages being a more efficient design, the disadvantages being a knocking noise on idle and vibration into the cabin.

Stattlers did not concur with the DMF being knackered after 300bhp and put my original DMF back in with my Sachs and Wavetrac as there was nothing wrong with it. Certainly, 10,000 miles on and it is fine 

[alackofspeed]

Dual mass means simply that one part of the flywheel is bolted to the crankshaft, whilst another part of the flywheel has limited angular spring loaded freedom relative to the crank.

The output from a crank is not smooth, and the dual mass serves a sprung mass damper to reduce very transient torque spikes seen by the gearbox. To my knowledge Dual mass flywheels are used for noise and drivetrain preservation purposes. Some of the most modern diesels that would historically have requred a DMF for NVH reasons, now have SMFs having had the combustion cleverly tuned to minimise torque spikes.

There are some pretty good diagrams on the interweb: