How Light is Your Flywheel+Clutch?

[mikefocke]

Pray tell what benefit would Jake have re the dual mass versus lightweight flywheel choice. He makes neither so no financial incentive. And since he has been inside more failed engines than most posters here, he just might have some insight. That PCNA advises against it in a TSB also adds to the weight of the dual recommendation. Maybe if you have rebuilt your engine and balanced it to a micro ounce or if you just happened to get one balanced that way from the factory, you may be in the group that has a positive experience with the light weight flywheel. Or not...

Your car, your money, your choice.

[WillH]

Isn’t there a harmonic balancer pulley available for the M96?

[JFP in PA]

Originally Posted by WillH

Isn’t there a harmonic balancer pulley available for the M96?

Yes, but it is not equivalent to the action of the dual mass flywheel.

[particlewave]

It seems he's removed the post from his site, but here are the pictures that google has saved:

[j.fro]

I installed the LWFW at 142000. At 189000 no problem with that ( do have a cracked head). 9 years of competitive autocrossing and all of the beating that goes with it.

[thstone]

Originally Posted by particlewave

It seems he's removed the post from his site, but here are the pictures that google has saved:

Do you know if those photos are from a Boxster? My memory wants to say that is a 996 engine but ... I'm lucky to remember my home address these days.

[particlewave]

I don't recall, just that it was an M96 with a lightweight flywheel.

[Lew]

Porsche wanted the lightest crank they could have and those cranks cannot stand the huge torques both in Revs and downshifting loads. Many light weight flywheels installed have caused the cranks to fail.

[maytag]

Originally Posted by Lew

Many light weight flywheels installed have caused the cranks to fail.

Can you cite more than one?
In the WHOLE of the internet, I can find only one.
Please, show me "many".

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[JFP in PA]

Originally Posted by maytag

Can you cite more than one?
In the WHOLE of the internet, I can find only one.
Please, show me "many".

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We have seen a couple, but also do not post everything we see on the web.....

[Lew]

Which one are you talking about Maytag? I remember reading a couple of articles about the reason cranks broke, and others that spoke of hearing about broken cranks that were light flywheel related were in a public conversation. I somewhat remember the article I read, and if I can find it, I will post it up for you to read. If it's a different article that you mention, that's two of the many.

[maytag]

Originally Posted by Lew

Which one are you talking about Maytag? I remember reading a couple of articles about the reason cranks broke, and others that spoke of hearing about broken cranks that were light flywheel related were in a public conversation. I somewhat remember the article I read, and if I can find it, I will post it up for you to read. If it's a different article that you mention, that's two of the many.

belongs to "ltusler" over at renntech. this it "the one" that Jake Raby has posted about, including photos of it, and that everybody seems to always be referring to when they say that they know somebody whose crank broke because of a LWFW.

FWIW: it seems (as I read about it) that they were building a track motor, with a number of other modifications to the motor. It's also a 996 motor, so, more HP / torque being driven through that crank to begin with. Somehow the crank failure gets pinned on the LWFW, in spite of literally HUNDREDS of others that have used the LWFW without incident.

Here's the quandry I find myself in: I am not going to be able to do all of the testing myself.... and it would be foolish to do so anyway, when others have already done it. So I have to / get to rely on the findings of others. And frankly: the number of successes with a LWFW FAR outnumber the anecdotal evidence of failures. I say anecdotal, because, while I can (and have) talk with MANY, MANY who've had a success with the LWFW, I can find only ONE person who actually has a failure story.

JFP has just indicated that he has seen a few. I don't doubt he has. but this still resides in the somewhat nebulous territory of "I heard about", since I don't know any specifics (like mileage, other mods, usage, etc etc). On the other side: I can get all SORTS of details and specifics about the many people who have and are using a LWFW with success.

So as a newcomer, relying on what others have learned, what result SHOULD I come to?

[JFP in PA]

Originally Posted by maytag

belongs to "ltusler" over at renntech. this it "the one" that Jake Raby has posted about, including photos of it, and that everybody seems to always be referring to when they say that they know somebody whose crank broke because of a LWFW.

FWIW: it seems (as I read about it) that they were building a track motor, with a number of other modifications to the motor. It's also a 996 motor, so, more HP / torque being driven through that crank to begin with. Somehow the crank failure gets pinned on the LWFW, in spite of literally HUNDREDS of others that have used the LWFW without incident.

Here's the quandry I find myself in: I am not going to be able to do all of the testing myself.... and it would be foolish to do so anyway, when others have already done it. So I have to / get to rely on the findings of others. And frankly: the number of successes with a LWFW FAR outnumber the anecdotal evidence of failures. I say anecdotal, because, while I can (and have) talk with MANY, MANY who've had a success with the LWFW, I can find only ONE person who actually has a failure story.

JFP has just indicated that he has seen a few. I don't doubt he has. but this still resides in the somewhat nebulous territory of "I heard about", since I don't know any specifics (like mileage, other mods, usage, etc etc). On the other side: I can get all SORTS of details and specifics about the many people who have and are using a LWFW with success.

So as a newcomer, relying on what others have learned, what result SHOULD I come to?

You need to also remember that 90% of the single row cars never suffered an IMS failure either, but that 10% number is still very significant if it is you...…..

Porsche actually released a bulletin to dealers warning them not to warranty engine failures if the car has a single mass flywheel in it. The problem is somewhat more than "nebulous"...…………..

[MWS]

This discussion raises the "performance vs robustness" argument. As I always mention, to each their own, but I gravitate toward longevity as I personally abhor failure that could be avoided, but then again, performance isn't my primary goal. As such, my decisions are left primarily to engineering (or my common sense version of form, function and durability) and in this limited case, I personally vote for the heavier flywheel (more robust) versus a lighter option that has *maybe* a few failures attributed...as even one failure would lead me to believe that this isn't the best design option. Again, I'm not the type of person to require volumes of information to prove (even if I want to believe otherwise) a failure *could* be extrapolated across an entire sample. I don't need to hit myself in the head with a hammer multiple times just to prove that indeed the first one truely hurt.

Regarding your choice (and again, to each their own), perhaps weigh the tangible performance improvements versus possibly having to do this all again....and forgive me for saying so, but it seems like you are in the "want to believe" camp (which for me always leads to poor decisions and/or injury); try to remove any preconceptions and just perform a mental pro/con analysis.

Whatever you decide, I always salute your wrenching, tinkering and thinking outside the box. You are also prone to call "BS" on a Porsche hardliner (which always makes me secretly smile); apply that same challenging thought process to yourself and I'm sure you will find your answer.

Let us know, and as always, I look forward to being completely and totally wrong. Lol.

[maytag]

Originally Posted by MWS

This discussion raises the "performance vs robustness" argument. As I always mention, to each their own, but I gravitate toward longevity as I personally abhor failure that could be avoided, but then again, performance isn't my primary goal. As such, my decisions are left primarily to engineering (or my common sense version of form, function and durability) and in this limited case, I personally vote for the heavier flywheel (more robust) versus a lighter option that has *maybe* a few failures attributed...as even one failure would lead me to believe that this isn't the best design option. Again, I'm not the type of person to require volumes of information to prove (even if I want to believe otherwise) a failure *could* be extrapolated across an entire sample. I don't need to hit myself in the head with a hammer multiple times just to prove that indeed the first one truely hurt.

Regarding your choice (and again, to each their own), perhaps weigh the tangible performance improvements versus possibly having to do this all again....and forgive me for saying so, but it seems like you are in the "want to believe" camp (which for me always leads to poor decisions and/or injury); try to remove any preconceptions and just perform a mental pro/con analysis.

Whatever you decide, I always salute your wrenching, tinkering and thinking outside the box. You are also prone to call "BS" on a Porsche hardliner (which always makes me secretly smile); apply that same challenging thought process to yourself and I'm sure you will find your answer.

Let us know, and as always, I look forward to being completely and totally wrong. Lol.

MWS, dude.... what a GREAT post.

Yes.... I'm guilty, as charged, of being squarely in that "want to believe" camp. And I've used LWFW on dozens of engine builds (not Porsche) and feel like I have a pretty good knowledge base. This also moves the needle for me. So yes, I also have an "agenda".

But I'm truly open to being moved to another camp. Especially if it saves me a motor! Haha.
I like your comment about there being a trade between longevity and performance. For me, the needle swings further away from longevity, and towards performance than for some others. I don't think I'm anywhere near "devil be dammed" on the scale though; somebody sway my opinion with some hard data, I'm not going to ignore it. I understand the science behind the argument, but I just don't see the data backing it up. In fact, I see the data debunking it.

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[maytag]

I picked up my flywheel and pressure plate from my machinist, who was balancing them for me.
For what it's worth: the aasco flywheel was very close to balanced already: less than 1/2 gram out. The SACHS sport pressure plate was about 3 grams out. But now we're dialed-in.

[Robert986]

I guess I love old threads..

So, how did this end up? Happy times or crank in pieces???

[maytag]

Originally Posted by Robert986

I guess I love old threads..



So, how did this end up? Happy times or crank in pieces???

Happy times. Very happy times. Nothing but lots and lots of very happy times.

(Any awards for thread resurrection? )

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[nuvolari]

Originally Posted by maytag

Happy times. Very happy times. Nothing but lots and lots of very happy times.

(Any awards for thread resurrection? )

Enjoyed this thread but I have an unrelated question:

You mention installing your IMS bearing towards the end and curious which IMSB you used?

[ike84]

Lari, if you have an unrelated question, please post it in a new thread (or read the thousand imsb threads already published and make an educated decision for yourself). This is an exceptionally valuable thread and it should stay that way.

Yes, I'm an ****************************. No, I won't apologize. Since the moderators are now non-existent, someone has to say it.

On a related note, I'm curious to know if anyone has quantified the performance advantage of the lwfw with sprung clutch? Dyno results, track times, LTFT data, etc.

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