How Light is Your Flywheel+Clutch?

[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"...…………..

[Lew]

This is what I remember reading regarding a broken crankshaft referring to a light flywheel. I certainly would take the author's advise in what he is saying in the last paragraph of this article.


WOW, this is one of the more extreme failures I have ever witnessed from any engine.... Its not too often that a crankshaft shears on the track on an engine that has 7 main bearings, but this one damn sure did!

The engine has the 3.6 X-51 package and was making 325 RWHP and had seen TWELVE THOUSAND track miles prior to this failure. We had initially thought the engine had broken a rod due to the material that came from the oil sump, but as soon as the engine arrived at our facility a 5 minute inspection found the crankshaft to be in two pieces!

The material these cranks are made from is powdered metal, it's what most modern engines use for crankshaft and connecting rod materials and I am less than impressed with it thus far. I can't believe that a component with such mass could break so extremely.

I feel that this failure was attributed to by a couple of things-

1- The engine was "upgraded" to a lightened flywheel. This new flywheel was installed onto the existing stock engine without being balanced to that assembly. This created an imbalance in the rotating mass AND it did away with the factory dual mass flywheel.

2- The dual mass flywheel was removed to alow the single mass lightened unit to be installed. This eliminated ALL MEANS OF HARMONIC DAMPENING!! The crankshaft was forced to absorb ALL harmonics from the engine and transaxle when the dual mass unit was removed..

So- adding the light weight flywheel was a double negative, not only did it create imbalance, it also eliminated the harmonic dampening of the dual mass arrangement.

Due to this I feel that adding a lightweight flywheel to any existing engine is not a wise decision, and that they should only be added when the entire rotating mass can be balanced and indexed to accomodate the lightweight unit. This means engine disassembly, so I'd only add one of these when doing one of our performance upgrades so the entire assembly can be precisely balanced.


Jake Raby

[maytag]

Originally Posted by Lew

This is what I remember reading regarding a broken crankshaft referring to a light flywheel. I certainly would take the author's advise in what he is saying in the last paragraph of this article.


WOW, this is one of the more extreme failures I have ever witnessed from any engine.... Its not too often that a crankshaft shears on the track on an engine that has 7 main bearings, but this one damn sure did!

The engine has the 3.6 X-51 package and was making 325 RWHP and had seen TWELVE THOUSAND track miles prior to this failure. We had initially thought the engine had broken a rod due to the material that came from the oil sump, but as soon as the engine arrived at our facility a 5 minute inspection found the crankshaft to be in two pieces!

The material these cranks are made from is powdered metal, it's what most modern engines use for crankshaft and connecting rod materials and I am less than impressed with it thus far. I can't believe that a component with such mass could break so extremely.

I feel that this failure was attributed to by a couple of things-

1- The engine was "upgraded" to a lightened flywheel. This new flywheel was installed onto the existing stock engine without being balanced to that assembly. This created an imbalance in the rotating mass AND it did away with the factory dual mass flywheel.

2- The dual mass flywheel was removed to alow the single mass lightened unit to be installed. This eliminated ALL MEANS OF HARMONIC DAMPENING!! The crankshaft was forced to absorb ALL harmonics from the engine and transaxle when the dual mass unit was removed..

So- adding the light weight flywheel was a double negative, not only did it create imbalance, it also eliminated the harmonic dampening of the dual mass arrangement.

Due to this I feel that adding a lightweight flywheel to any existing engine is not a wise decision, and that they should only be added when the entire rotating mass can be balanced and indexed to accomodate the lightweight unit. This means engine disassembly, so I'd only add one of these when doing one of our performance upgrades so the entire assembly can be precisely balanced.


Jake Raby

Once again, we take the word of someone with an agenda (Jake raby) over hundreds of others with a successful record.

Look: if this were a widespread problem and everyone was trying to understand it, Jake's explanation would absolutely fit, and we could all put it to bed. But when his explanation is (as you showed us below) postulated to explain a single, specific failure, and then we ascribe it to ALL OTHER SITUATIONS ..... ignoring all of the rest of the successful uses, then we are fools.

Let's think like scientists for a moment, shall we?
We have hundreds of experiments, with as many variables. We have ONE failure (of the hundreds of tests). We blame ONE of the variables because it seems to make sense. We'd never get past peer review. Ever. If we published, we'd be laughed to shame.

All I'm asking for is more data. Not more requests that I just trust Jake.

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[MWS]

Originally Posted by maytag

Let's think like scientists for a moment, shall we?
We have hundreds of experiments, with as many variables. We have ONE failure (of the hundreds of tests). We blame ONE of the variables because it seems to make sense. We'd never get past peer review. Ever. If we published, we'd be laughed to shame.

I'm a big fan of the scientific method (as it relates to OTHER people, lol), but I'm just too darn risk adverse to experience failure after failure just to prove a hypothesis to myself. I previously mentioned the example of hitting myself with a hammer, once is enough...now Im picturing a room full of scientists whacking themselves in their heads with hammers to replicate results then moving to another peer review group poised with hammers in hand and heads on the tables. Lol.

Also, I'm not in the camp of trusting one person, as even an "expert" has to pass my mental review process. I guess what I'm asking is "what design seems better to you, at least from a common sense point of view?" Using that criteria, you'll always be right...or at least for a few minutes.

[maytag]

so now I'm looking at catalogs, and I'm forced to look at the cost:benefit as well. It looks like (just using Pelican as a source) I'm gonna spend most of $1000 MORE to do the LWFW and associated sprung-clutch, versus just replacing with stock-type components. (some of this is because of what looks to be a real bargain on a LUK clutch kit right now.)

is the increased performance, and the associated potential risk exposure, worth $1000 to me right now? (That's the question I'm posing to myself)

::sigh:: I hate it when I start to get pragmatic.

[WillH]

What is the difference in rotating mass?

[maytag]

Originally Posted by WillH

What is the difference in rotating mass?

From post #1 in this thread:

Lightweight Flywheel only - 13.0 lbs.
Lightweight Flywheel + New Sachs Clutch Assembly - 25.4 lbs. *
Stock Dual Mass Flywheel only - 26.5 lbs.
Stock Dual Mass Flywheel only + New Sachs Clutch Assembly - 38.8 lbs.
Lightweight Flywheel + New Sachs 4 Spring Clutch Assembly - 18.0 lbs.

[Lew]

Originally Posted by maytag

so now I'm looking at catalogs, and I'm forced to look at the cost:benefit as well. It looks like (just using Pelican as a source) I'm gonna spend most of $1000 MORE to do the LWFW and associated sprung-clutch, versus just replacing with stock-type components. (some of this is because of what looks to be a real bargain on a LUK clutch kit right now.)

is the increased performance, and the associated potential risk exposure, worth $1000 to me right now? (That's the question I'm posing to myself)

::sigh:: I hate it when I start to get pragmatic.

I just gotta laugh at this....The name Maytag fits you perfectly....Wishy Washey!

The Devil made me do it!

5 to 1 odds you don't do it! Anyone else think that?

[maytag]

Originally Posted by Lew

I just gotta laugh at this....The name Maytag fits you perfectly....Wishy Washey!

The Devil made me do it!

5 to 1 odds you don't do it! Anyone else think that?

ahhh, say what you will, Lew.... but when I make the decision, it will be a decision I've made after I have considered ALL of the risks, benefits, costs, etc. Not because I have joined the rest of the sheep. Your silly taunting aside.

If cost is of no importance to you, congratulations. But cost (value) is ALWAYS a consideration for me. It WILL always be so. I'd enjoy you explaining to me why it shouldn't be thus, but I assume you would merely quote someone else again, since so far I haven't seen you present any of your own original thinking to the matter. Again, your silly taunting aside.

For the record: "Maytag" comes from being the guy who can fix or build ANYTHING track-side. I'd stack that name up against "lew" all day, and twice on Sundays. Since you asked.

[BYprodriver]

Originally Posted by maytag

so now I'm looking at catalogs, and I'm forced to look at the cost:benefit as well. It looks like (just using Pelican as a source) I'm gonna spend most of $1000 MORE to do the LWFW and associated sprung-clutch, versus just replacing with stock-type components. (some of this is because of what looks to be a real bargain on a LUK clutch kit right now.)

is the increased performance, and the associated potential risk exposure, worth $1000 to me right now? (That's the question I'm posing to myself)

::sigh:: I hate it when I start to get pragmatic.

Don't forget the cost to have the flywheel balanced, they are often way out of balance.

[maytag]

Originally Posted by BYprodriver

Don't forget the cost to have the flywheel balanced, they are often way out of balance.

Yup. My machine shop is on standby. :-)

[maytag]

Originally Posted by JFP in PA

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"...…………..

Thanks JFP. to be clear, I'm not suggesting the problem is nebulous, but rather that the citations and references used when describing crank failures are. They almost NEVER come with pertinent details, with only one exception, and that being the sole, lone, single verifiable instance of a crank failure being attributed to a LWFW.

And lew just made the point. He cited "MANY", yet when pressed, he came back to the same one. ONE.

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