Looming DMF Failure

Retrogamer

I always dip the clutch when starting the car to take the load off the starter and battery, but going forward i'll do the same when switching the engine off. Thanks

atrixblue.-MFR-.

Ultrasonic wrote: »

One common bit of advice to prolong the life of a DMF is to have the clutch pedal depressed when starting and stopping the engine. (There was some detailed study showing that significant DMF wear occured at these time without depressing the clutch, but I can't find the link quickly, sorry.)

As for SMF conversions, my concern would be whether this would be more likely to lead to a gearbox failure? Isn't part of the point of a DMF to protect the gearbox?

nope, SMF conversions dont harm the box at all, the DMF acts as a buffer taking load off the engine when pulling off giving a smoother more refined less juddery feel and take load of the friction plate, trouble with SMF conversions is that it can potentially wear out a OEM clutch quicker, as that dampening buffer is no longer present, and the clutch friction plates tend to have smaller springs in it because the manufacturer is relying on the DMF buffer aswell, remove the DMF and more load goes to the friction plate.

many clutch manufacturers have their own "KIT" like LUK, they will have the friction plate modified with a heavier duty friction plate and pressure plate to go with the SMF they developed.

downside to SMF convertions if people report that they feel more vibration through changing gear and at idle.

some kits you cant mix n match like sachs, they do a SMF and a clutch kit that will only fit their kit on some applications, so you cant use a luk clucth kit on a SMF flywheel for eg.

OP i didnt notice my DMF had worn past its life, 1.8 petrol engine, only noticed that uphill was getting to be a struggle and "pinking" from the clucth on engagement of gears and clutch slippage. i replaced everything there after when i went do the clutch as most was either failed or the hydraulic system was knaffed aswell (sealed system run dry of hydraulic fluid).

forgotmyname

Alias_Omega wrote: »

Apparently £320 from here for the whole kit for a Mondeo ST 2.2 TDCI, but google reviews said to stay well clear of them. Instead we looked at LUK parts from genuine part sellers (GSF etc). The labour was 7-8hours to get it out and back in... nice eh..

Single Flywheel... Maybe in a Ford Transit Van. Never drove one, so cant comment.

OH GOD NO.... Dont buy anything from Techniclutch... Make a complaint and they will change the company name AGAIN... and ignore you.

Melt some chocolate and make yourself a new clutch kit. Use the leftover chocloate from your teapot making .

A clutch from them and chocolate teapots have something in common. Have a guess.

Ultrasonic

atrixblue.-MFR-. wrote: »

nope, SMF conversions dont harm the box at all,...

Surely a DMF must reduce the vibration transmitted to the gearbox, and so removing this must at least increase the risk of gearbox damage? Sites like this certainly seem to think this is the case:

http://www.torquecars.com/tuning/dmf-solid-flywheel.php

forgotmyname

If the SMF kit is lighter than the DMF kit then your putting the engine out of balance.
The heavy crank damper will no longer be the correct weight to balance and dampen out vibrations.

The clutch plates will need to have springs to dampen vibrations when taking up drive but will do nothing when actually on the move.

Personally i wouldnt bother with an SMF unless building the engine and balancing it from scratch with a lighter crank pulley also.

atrixblue.-MFR-.

Ultrasonic wrote: »

Surely a DMF must reduce the vibration transmitted to the gearbox, and so removing this must at least increase the risk of gearbox damage? Sites like this certainly seem to think this is the case:

http://www.torquecars.com/tuning/dmf-solid-flywheel.php

have a think about it.

how many cars with solid flywheels do you know that have been the main cause to gearbox failure without a manufacturing fault or high heat damage produce by tuning?

do you believe everything that the interweb says?

out the many my ex works sold, we had none cause gearbox damage, engine damage, only reports we had back was it was noticeably different to gearchanges and vibration (and im not talking teath chattering vibration just low rev bogging out vibration when crawling wich you dont notice with DMF).

tuning your car, if you get BHP up considerably its recomended you remove the DMF for a solid one, as the power retention can actually blow up the cogs in the DMF and destroy the gearbox casting (bell housing) and also fit a fast road or competition paddle clutch.

there really is no need to fit a DMF to a car, other than refinement and a dmf will hold your revs rather than let them drop off allowing for you to keep the car in gear at lower revs and make the diesel engine that little bit more quiet and less juddery at idle. honestly, reverting your car back to a SMF, is nothing to be concerned about in terms of causing other damage such as broken gearbox's and damaged engine

the vibration transmitted around the SMF is noticeably more but not enough to juddger the internal gear cogs to skip a tooth, or dislodge the bearings or snap the lay shaft or selector problems or disturb synchro's so much everything crunches on gears selection.


more so now these generation of SMF's are balanced and wieghted, where as the first revertion kits werent they allowed throw out of the crank etc wich i never experienced in selling these kits BTW, is what you maybe getting at, but now these SMF have been made to a degree that you hardly notice the difference from DMF to SMF.

GolfBravo

atrixblue.-MFR-. wrote: »

how many cars with solid flywheels do you know that have been the main cause to gearbox failure without a manufacturing fault or high heat damage produce by tuning?

You have to remember that most modern cars feature DMF as standard, and therefore most modern transmissions these days are designed to work with DMF only.

Since DMF offers lower transmission loading, manufacturers can now build smaller transmissions - they are smaller and lighter at the cost of durability. If you are to fit a SMF to a car that is designed for DMF only you are likely to experience gear rattle and droning, especially that most diesels are driven below 2000rpm (this is where you get the most engine irregularity).

Also, modern engines have crankshafts designed to work with DMF - the DMF reduces crankshaft vibrations, both torsion and bending. No DMF = more vibrations.

GolfBravo

Retrogamer wrote: »

I always dip the clutch when starting the car to take the load off the starter and battery, but going forward i'll do the same when switching the engine off. Thanks

You should also keep an eye on the starter and battery - make sure they are in good condition.

One of the major things killing DMFs is resonance amplitude - when you start a diesel engine it briefly goes through a resonance (vibration) sequence. The weaker the battery/starter the longer and stronger the resonance. To minimise resonance you need as much torque from the starter as possible.

atrixblue.-MFR-.

GolfBravo wrote: »

You have to remember that most modern cars feature DMF as standard, and therefore most modern transmissions these days are designed to work with DMF only.

Since DMF offers lower transmission loading, manufacturers can now build smaller transmissions - they are smaller and lighter at the cost of durability. If you are to fit a SMF to a car that is designed for DMF only you are likely to experience gear rattle and droning, especially that most diesels are driven below 2000rpm (this is where you get the most engine irregularity).

Also, modern engines have crankshafts designed to work with DMF - the DMF reduces crankshaft vibrations, both torsion and bending. No DMF = more vibrations.

i sold over a 3 year period probably about 2000 SMF kits to replace a DMF, we sold national, LUK and sachs, i have never, not im my 3 year period had a warranty issue or heared of catastrophic failure of crank and gearbox or clutch as a direct result of excess vibration or excess loading on a gearbox or crank.

i heared stories of the earlier development of SMF kits could cause crank throw, this was when the SMF kits were relatively new not balanced or weighted to mimic DMF weight and balance specs.

kits are have now been produced with such precision that you barely notice any vibration at all my BIL golf has a SMF conversion in it and you cant tell it has been converted.

my BIL was my ex employer at motor factors, he has never had a SMF or DMF come back that has caused a malfunction to engine parts or gearbox parts, he sold 1000's up untill his redundancy 2 month ago.

once in gear the DMF is engaged, if you have engine irregularity at 2000rpm there is something wrong with that engine, besides the SMF, and lets face it if you tumbling along in 3rd 4th or 5th gear at 2000rpm doing -15MPH what engine wouldnt struggle.

anything can cause vibration broken mounts or a missfire etc that can cause more violent vibration to the engine, than a SMF, theoretically by your post that should cause imediate failure, but ive never heared of a engine or gearbox explode as a result of a mount or misfire.

GolfBravo

atrixblue.-MFR-. wrote: »

once in gear the DMF is engaged, if you have engine irregularity at 2000rpm there is something wrong with that engine, besides the SMF, and lets face it if you tumbling along in 3rd 4th or 5th gear at 2000rpm doing -15MPH what engine wouldnt struggle.

Figure 5 illustrates the wide open throttle characteristic curve of a typical diesel engine. For a conventional drive train, the additional dynamic torques as a result of the irregularity are superimposed. Depending on the speed, they can generate more than 10 % additional load.

Source: Schaeffler

atrixblue.-MFR-. wrote: »

anything can cause vibration broken mounts or a missfire etc that can cause more violent vibration to the engine, than a SMF, theoretically by your post that should cause imediate failure, but ive never heared of a engine or gearbox explode as a result of a mount or misfire.

By my post? Immediate failure? Where does it say that?

Further reading:

... a worrying trend taking place with the incorrect replacement of original equipment specification dual mass flywheels with lower cost and incompatible solid flywheels.
...
While the difference is not noticeable on some vehicles, the finely tuned variation in harmonics balance between the engine and gearbox is completely lost by this practice. This leads to the eventual wearing of gears to more expensive major drivetrain problems over the long term.
...
There is no advantage to fitting a solid flywheel in the place of a dual mass flywheel which was invented by LuK for the very purpose of achieving total balance between the engine and gearbox harmonics. While more expensive than solid flywheels, the long term cost of replacing the correct component far outweighs the labour and component costs of returned customers along with the greater problems that this practice can cause down the track.
...
One of the biggest problems with replacing a dual mass flywheel incorrectly with a lower cost solid flywheel is that in most cases there is no audible difference or vibration change. The harmonics involved cannot be sensed by the driver.

Source: Schaeffler