406oc.co.uk

Hi guys,

Clutch/flywheel need replacing in my '6, and I am very tempted to do a solid conversion. After the remap to 140hp/320nm there is a lot of judder and some clutch slip, so I wondered if it was wise to convert to a solid flywheel which will handle the extra power/torque better. However, I've heard terrible things about it killing cranks, which I'd hate to do ofcourse! Any advice? Those who have converted, hows it been?

Benjamin

The early Hdi's in the Xantia had a solid flywheel and seem to be fine. The only thing I have noticed about the Hdi in comparison with the XUD 2.1td is vibration at low revs, if you accelerate hard at less than about 1500 rpm it doesn't like it, the 2.1 would pull smoothly almost from tickover and I personally think its because the Hdi flywheel is to light. If the solid flywheel is any lighter than the DMF I would suspect it would make it worse.

Peter

The vibration is usually torque overload. A remapped diesel can produce enough torque to take up all the 'give' in the dmf so you effectively have a solid flywheel. Bear in mind the clutch on a car with a dmf has no springs to absorb driveline shocks and you have the worst of both worlds.
A better quality, more progressive map can overcome this, at a price. Realising the throttle is not an on/off switch does so more cost effectively while leaving you the option of exploiting massive mid range torque when the need arises.

Dmf or not? You'll find lots of people who swear there's no downside to fitting a solid flywheel. I've had the choice twice and opted to keep the dmf on both occasions. You're only going to do this once in the life of your car, so there's no likelihood of it being cheaper next time. Fitting a conversion to a 2.2 isn't any cheaper than a dmf+clutch replacement, plus there is credible evidence of increased harshness, vibration and at least a theoretical risk of snapping a crank if you do opt for solid.

All in all I couldn't see any good reason to change, but this is only my opinion.

DMF it is, I love the smoothness of the HDi and would hate to make it vibrate. Will the 140hp/320nm be an issue for a DMF? Also, I've heard that the DMFs dont like low revs, I try to keep it above 1500rpm all the time which is where the boost is, is that too low?

fattail95 wrote:DMF it is, I love the smoothness of the HDi and would hate to make it vibrate.

You obviously haven't driven a 2.1XUD then.

Peter

PeterN wrote:

fattail95 wrote:DMF it is, I love the smoothness of the HDi and would hate to make it vibrate.

You obviously haven't driven a 2.1XUD then.

Peter

I haven't I'd love to though, however I wouldn't say the HDi is rough, smooth power and torque delivery from 1000rpm with the dual mass, and no buzzing/vibrating unless its past it (which mine is now).

Doggy, which flywheel brand would you consider the best? I've heard a lot of good things about Luk, what's your thoughts?

Thanks!

I've just had the flylweel done on the 407 (which has a newer version of the 2.2 engine from the 406), and went for LUK DMF and matching (obviously) clutch. Every mechanic I asked told me, without hesitation, not to go solid. (It sounds like solid conversions cause a lot of trouble on VAG cars.)

As far as I understand it, the DMF is there to protect the gearbox from 'pulsing' from the engine -- not for your comfort and convenience! This problem is worst in engines with a low number of cylinders (i.e., 4) with high torque output (i.e., diesel). Engines with more cylinders traditionally have smaller flywheels.

My HDi 90 406 had a solid flywheel (as all 90s do) and I had no issues with it, and can't tell any difference in the 407 for having a DMF. The 406 pulled from 1200 without vibration (or at least it did when it was new, and again after I had the bottom mount replaced).

I believe jasper5 prefers LUK kits, so that's all you need to know about that!

Is it a bad idea to double de-clutch with a dmf or does it no matter?

Treated sensibly they will last, my 406 has its original as far as I know and that's on 230,000 miles.

Peter

LUK are the original manufacturer of Dual Mass Flywheels.

LUK clutch and flywheel matched as a set is the way to go.

Double de-clutching won't make any difference to A DMF, but why would you do that?

jasper5 wrote:LUK are the original manufacturer of Dual Mass Flywheels.

LUK clutch and flywheel matched as a set is the way to go.

Absolutely agree with that. Low revs aren't the real issue, your DMF works hardest when starting and stopping the engine.

Its not that I do lol just askin if it would have negative affects. Trying to improve my knowledge is all[WINKING FACE]

Just to throw my 10 penneth worth in,mine has a solid flywheel conversion and I've done over 30k miles with it some of which has been towing a caravan and I've had no problems at all,the car has had the 140 map for 20k miles of them.If were to be picky there is a slight tad of vibration at around 1200 rpm when decelerating but I wouldn't put it down conclusively to the flywheel.

^ same here, done now over 10k miles with solid fw and 435nm, when it was changed only difference noticed at idle slightly more vibrations but increase rpm from 750 to 850rpm sorted it, now is hard to tell that its diesel and no change of rpm when ac kicks in