[oakgreen968]

Which setup would you choose and why?



968 Fidanza LW flywheel with stock solid clutch disk and stock pressure plate

advantages: lighter in weight (968 pressure plate is much lighter than the S2), retain 968 bellhousing.

disadvantages: gear noise?, unsprung clutch



OR



944S2 flywheel (lightened 2 lbs) with stock pressure plate and vertex clutch disk

Advantage: sprung clutch disk

Disadvantage: have to change torque tube (I do have the torque tube , PIA to change)



This is a street car, however it will be used in track events.



Question about the fidanza LW flywheel: I have had the engine dynamically balanced, and might run the S2 crank pulley for harmonic balancer (thoughts?) . Will this eliminate the 'gear noise' that everyone complains about when using fidnaza flywheel?

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[Dave]

There is another flywheel option from www.rsbarn.com to consider as well.



On the 968 development side...



In an August '92 article written by Mr. Herbert Ampferer, Chief of Engine Development at Weissach, he states: "torsional analysis of the crankshaft system with the lighter connecting rods and dual-mass flywheel showed that the fourth-order resonant frequency of the system fell outside of the engine's rpm range (figure 2.) Therefore the heavy and expensive torsional damper on the front end of the crankshaft could be deleted." This reduced rotating mass by some 2.5 kg.



Kind of interesting. I'd love to know what the graph looks like with motorsport flywheel...

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[flash]

i saw this same question posed on rennlist - the "resident authority" was very wrong when he said it had nothing to do with harmonics



it has everything to do with harmonics - it is the harmonics that cause the transaxle to rattle with a single mass flywheel - without them, it would be silent, and the loose tolerances of the gears would behave just as they do with the DMF



if it were only the transaxle, there would be no noise at a constant load - it is the pulsing that causes the brief unloading and deflection that results in rattle



saying it was the transaxle and not harmonics is like saying it's the soft skull and not the hammer smacking it that makes it hurt



i don't know if the harmonic balancer pulley would resolve it or not (the transaxle issue, not the soft skull- lol), but it works on other cars - every car i ever had (before the later german stuff) had one



as for dynamic balancing resolving the problem, this would be a very involved process, as you would also have to account for the balance shafts and their effect on the entire system



harmonics are very difficult things to play with, and require a lot of very expensive equipment to sort these kinds of things out - you could play with trial and error, but you would be risking failures of components along the way - absolutely balance a single mass flywheel and all such associated components, but don't expect it to be smooth as glass



all 3 of the single mass flywheels (porsche motorsport, rs barn, fidanza) result in similar noise - thus far there is no solution - i am working on one, but don't know how it will turn out yet - i should have a better idea in a few weeks



as for which way to go, the porsche motorsport unit is uber rare, and the S2 is a PITA - the fidanza is not approved for PCA racing (those that have it and are racing illegally will soon be getting into trouble), the rs barn unit is PCA approved - seems like a pretty easy choice to me



all that being said, i have the fidanza and am very used to the noise now, and barely hear it anymore - i do need a better clutch disk than stock though, as i have already fragged one - i do not plan to race this car

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[Renalicious]

So looks like it's either a DMF, or light weight flywheel + harmonic balancer to avoid transaxel noise? I'm getting the RS barn unit installed soon, so I guess I'll find out <img src="/forum/images/smilies/968/smile.gif" class="smilie" alt="" />

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[flash]

nobody has tried it yet, so i don't know if the balancer will solve the problem, or create new problems



as i said, i am working on a solution, but i don't know if i can get the part made or not, and how much it will resolve the problem - i might have a bead on it this week



i have noticed that my new exhaust has masked most of the noise, and yet is not much louder than stock - seems like more harmonics at play here, but acoustic ones

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[oakgreen968]

Thanks for all of the info guys!



I'm leaning towards going with the S2 flywheel and sprung clutch disk. I might try it without the S2 crank pulley - because that can be added in later.



Flash - why dont you post up your solution? I'm interested to hear it - custom work doesnt worry me as I've got access to a very large machine shop and a friend with years of experience (and hes also a mech-eng.)

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[flash]

well, as you are well aware, development of parts is a time consuming and expensive process - if it works, this one will be another part for the market - but, i'm not really looking to have somebody slip in underneath us and screw things up - there is already enough of that nonsense going on



so, while, i'm not really keeping it a secret, since i am working on this in tandem with pete, and he would be the retailer for it, i need to hold off until we have tested a prototype - i can say that if it works, it will work with his flywheel



it won't be too long - i need this worked out for myself too

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