I plan to run a lightweight aluminum flywheel ( after taking to a machinist to balance ) and a SPRUNG clutch disc.

Some yes, some no. Mine, no.

This is usually where someone calls me an idiot (or some equivalent) because I have the original IMS bearing AND an unbalanced LWFW! Its a timebomb!

http://i1114.photobucket.com/albums/...ps45fb9f1b.jpg

But it has 136,000 miles and 85 track days without a hitch. So far, so good.

http://2.bp.blogspot.com/-7tELCIzSja...tman66bomb.gif





http://x1.fjcdn.com/thumbnails/comme...08a309d51d.gif

I don't think this is an exercise in personal attacks, but a sharing of some hard learned information. You have had good luck, and that is a good thing. But others have not been so lucky, and some have experienced a disaster. Given the inconsistency in how these units seem to perform, I think it is a good idea that others be aware of it, particularly if they are paying someone to do the installation.

We do not do lightweight installations based upon our direct experience, that of other shops, and of course what Jake has seen. Porsche even released a dealer warning about the use of "single mass" flywheels, indicating that any damage would not be covered under warranty if the car still had one.

one person's 'luck' is another's 'caluclated risk'. folks have been taught to want black or white - it breaks or it doesn't. as soon as you get into 'it may break' you get conflict. people try to turn the grey into black or white. it 'may' break' turns into it 'won't' break or it 'will' break, and folks argue. 'i'm right' 'no i'm right'. you're both right. your both wrong. there are some that have broken, and some that have not. make a choice. try to base it on fact. ie, how may lw fw have broken vs how many are is use? ditto ims. ditto whatever. make your call based on risk vs reward - will a lw fw potentially fail sooner than a dual mass? perhaps. will it make driving more fun in the interim? perhaps. can you afford to deal with a failure if it happens? perhaps. ball it all up, make a decision and move on. all the feedback you get on the internet? worth what you paid for it. one failed flywheel with a sensational photo can morph into 'all lw flywheels fail' quite quickly out here in the ether. or a couple of success stories can send it the other direction (less frequently, however, as the interweb tends to attract the negative).

my personal story? i called the guys that made the dampened udps for gt3s and asked about an m96 application for use with lw fws and they told me that there was absolutely no need. i mean, is the oem flywheel dual mass in order to dampen harmonics, or is it heavier in order to allow use of a lighter unsprung clutch? it is a hairdressers car after all ...

Well played sir, well played

So what type of flywheel was on the batmobile? That is the way I'm going with my flywheel.

IIUC Porsche combined the effect of the front pulley harmonic balancer AND the springs in a traditional clutch disc in their dual mass flywheel. I suppose you could put on a single mass flywheel if you use a "sprung" clutch disc and a harmonic balancer belt pulley up front.

"Luck" also plays into it in a way very few even think about. By Porsche standards, the M96/97 engines are mass production items, and tend to have "broader" tolerances is several areas, including how well they are internally harmonically balanced. Unlike the Mezger lump that used to be used in the Turbo cars and is still in production in the cup cars, and which are refined to a very high standard, the M96/97's are not as closely held to the ideal specs. That is one of the many reasons the Metzger will set you back $50+K for a replacement, while an M96 is in the $15K range. Net result is that some M96/97's naturally produce more rotating assembly harmonics than others. And if "luck" has it that yours is one of the high harmonics engines, pulling the dual mass creates a lot more stress on the assembly. Plus, if your "luck" is really bad, and you get one of the lightweight units that is 10 or more grams out of balance on its own, it can become a recipe for a disaster.

When M96's are torn down and sent out to be internally balanced, some are pretty good, others not so much and require a lot more time in the machine shop to get them where they need to be. And it is a totally a matter of "luck" which one it will be......

THAT made my night. Thanks.....:cheers:

For the record..........I WAS going to go with a LWF but after researching it (beyond exploding motors, many guys had ongoing issues as a result of putting a LWF in) and coming to the conclusion it wouldn't be of any benefit to a street driven car I purchased a LUK Dual Mass unit off of Fleabay for significantly less than I could find anywhere else. I installed it along with a Sachs clutch kit in my 993 a couple of years ago, all is fine.

Lastly, I forgot to mention that if you do indeed test your DMF for in spec deflection and it passes with flying colors like mine did with ~35k miles on it (while I did the IMS bearing upgrade in my Box), you can simply clean it up with a palm sander since it cannot be resurfaced.

http://i46.photobucket.com/albums/f1...leanedFlyW.jpg

Dual mass actually can be resurfaced but the surface where the friction material touches must be clamped down in a fixture so it will not move. Here in OC there a couple guys who will do it, but shop around. the prices I found were as high as $450 and a low as $75.