In message , Jethro_uk
writes
On Wed, 03 Jul 2019 10:02:31 +0100, NY wrote:

"Bill" wrote in message
tairs...
With the first Octavia, I was planning to get the DMF changed to a
proper flywheel (Skoda do one for taxis), but other things went wrong,
so I traded it in. We still have the newer one and at just over 100k
miles, the "feature" is there, but liveable with.

What are the advantages and disadvantages of a dual mass flywheel?
https://en.wikipedia.org/wiki/Dual-mass_flywheel seems to imply that
with a high-torque-at-low-revs engine (a diesel) a DMF is highly
desirable to absorb some of the peaks in the torque as each cylinder
fires. Is the disadvantage mainly that it is more complex and therefore
more costly?

I think the idea is it acts like a light weight for when the velocity of
the flywheel needs to change quickly, but a heavy weight when it's needed
to keep the engine stable. There are springs and weights involved which
are slotted into a recess in the flywheel. I'm guessing there are metal
fatigue issues around having to much around with the single casting of
the flywheel.

I wonder if a system with two flywheels might be better ?

I sometimes look at the "Briskoda" Skoda forum, where the general view
seemed to be that the SMF was far superior to the DMF on the diesel
Octavia.
OTOH, I discussed it with the local (usually excellent) agent, who said
they had fitted a couple of SMF's to taxis, and they had both returned
and reverted to DMF's.

The forum advocates of SMF's mostly appeared to have used the same
manufacturer for their non-OEM flywheels. My guess was that these
flywheels were heavier than the others.

Where I suspected a resonant frequency of the DMF flywheel masses and
springs, the effect was - for example - when waiting to turn right
across traffic, a gap appears and you let the clutch in sharply, there
is a bang and the engine stops dead. I wonder if there is some damping
on the springs which can fail.

I like boat diesels with really heavy flywheels. I suspect the lighter
mass of the DMF makes for a much more lively engine in a car.

--
Bill