Non-DMF in 1.6hdi 16v

[xsara92]

Would anyone have an idea how much of an issue is having a simple rather than a dual mass flywheel in a Xsara Picasso, 1.6hdi with 109bhp from 2005?

Clutch replaced along with a non-DMF at 95.3k miles....now up to 114.3k miles.

I'm wondering if there are any steps I could take to help my gearbox...I know next to nothing about gearboxes in general

When the clutch job was done (a pig job), they had to weld the gear linkage/pivot arm, in case that detail is relevant.

[MattBLancs]

So my understanding is that the benefit of the DMF is that it lessens the jolting of the gearbox that, particularly a modern diesel, engine imparts in it.

It's easy to think of an engine running at a constant speed (e.g 700 rpm idling) but the reality is this is in effect an average: the crankshaft accelerates on each power stroke (when one of the four cylinders goes, well "bang" to borrow the Suck-Squeeze-Bang-Blow terminology commonly used to describe the four strokes of each full cycle)

In between the power stroke acceleration, the crankshaft is slowing down again, old to be jerked faster when the next power stroke arrives.

Now this constant acceleration / deceleration / acceleration cycle is more severe in a diesel engine when the short sharp "bang" is more pronounced relative to the decelerating periods (I guess driven by the high compression of a diesel engine, it slows more readily)

The torque pulses are particularly damaging at low revs where they can be close to the resonant frequency of a typical gearbox's internals.
My understanding is the DMF in effect adds mass to the gearbox rotating components and so gives the assembly a lower resonant frequency.

There'th ends the lecture!

Translation:

Don't move the car on the engine's idle speed as, to a small extent, it's shaking the gearbox to bits!

[mickthemaverick]

As I understand it, the primary purpose of the DMF technology is to ease the angular momentum transfer between the engine and the gearbox. That being the case it would imply that fitting a traditional clutch will return that transfer to the traditional format, which will only have an effect if the gearbox has been designed to be more fragile expecting a DMF to soften the transfer of rotational energy. That is my thinking for what it's worth but it leaves the question Was the gearbox made less robust?

[MattBLancs]

I don't think it's particularly gearboxes are being made (cheaper and) weaker, more that we're getting more output from diesels than days of old, e.g. peak torque for:
1.9 litre XUD9TE = 201 Nm at 2250 rpm (source Haynes Citroen ZX manual)

Versus

1.6 HDi DV6 110 = 245 Nm at 2000 rpm (Haynes 307 manual)

So the corresponding acceleration / deceleration or angular momentum transfer pulses are bigger than they used to be.


Just to contradict myself: it is worth noting that the 110 bhp DV6 is bolted to a BE4 gearbox, whereas the 110 bhp variant of the older DW10 HDi would have the chunkier ML5 gearbox (the 90 bhp of both DV6 and DW10 both use the "weaker" BE gearbox)