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Old 11-08-2020, 05:54 PM   #1
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LWFW would love some pointers!

Iīm seriously considering putting on a lightweight flywheel.. As always I google like crazy first when trying things I havenīt done before ;-)

I know that it will be harder to use in daily traffic but this car is a bit track oriented.. Also know about the risk due to lack of harmonic damping. I plan to use a pulley with harmonic damper to mitigate somewhat. (Eg. RSS 608 - Harmonically Damped - Underdrive Performance Pulley Kit)

Sorry for my newbie questions..

1) How high do I really need to lift the car to get to remove the gearbox properly? I have a feeling I need to invest in a set of new, higher jacks..

2) I got an offer on a FW made in iron (4.5kg) whats the deal with a iron FW? Is it better/worse/other benefits related to the alu FW? is 4.5 unreasoneable light, am I better of with a little heavier?

3) The clutch.. Do I need a sprung clutch or can I use the oem? I guess my question is "should I" I understand that there will be some ratteling with the unsprung, but will it hurt the drivetrain?

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Old 11-09-2020, 02:51 AM   #2
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I will say 20 inches. 23 inches comfortable.
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Old 11-09-2020, 12:28 PM   #3
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I will say 20 inches. 23 inches comfortable.
Thanks man!
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Old 11-09-2020, 01:50 PM   #4
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Hello Robert,

There has been several documented crankshaft failures due to removing the DMFW as you will no longer have the harmonic balancer effect that is build into the DMFW..

However you may want to explore installing a front pulley that has a balancer build into it, I believe that some of the GT3's came this way from the factory, this should help you to counteract the bad harmonic vibrations that cannot be cancelled with a low weight flywheel.

Please note that by any means I am no expert on this subject.. but have been reading about for more than two decades ever since I installed a LWFW on my 1.5 Fiat X1/9 and then into a 3.0 Alfa V6, but somehow I chicken out on the 987CS ...LOL

One thing for sure is that you Will Love the way how quick the engine will rev up (and down..) after installing a LWFW..

Good luck with your project
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Last edited by Gilles; 11-09-2020 at 01:52 PM.
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Old 11-11-2020, 06:46 AM   #5
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I would skip the lwfw honestly. Even with the harmonic dampner, you still have the shock from the transmission if you aren't exact on your rev matching.

And yes you would want a sprung clutch disk.


Tranny out...20 inches is fine, but i agree around 2 feet makes working conditions more favorable.

I've got the job down to about an hour to remove, slightly longer to reinstall.
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Old 11-11-2020, 08:07 AM   #6
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I love my LWFW but in my situation everything was balanced as the engine was being built . I have no funny vibrations or issues other than at idle the transmission gear stack is noisy . It's just part of the process with this type of flywheel . If you or whoever is going to do the swap does NOT have the ability to balance I would hesitate going down this route .
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Old 11-11-2020, 09:41 AM   #7
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Not sure what lump the op has but I believe there is a thread on this forum where Jack Raby said the 2.5 is pretty much ok at handling the resulting harmonics from a lwfw, whereas the others required more balancing attention. Anyone have opinions about that?
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Old 11-11-2020, 10:48 AM   #8
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This might be worth perusing.
http://986forum.com/forums/boxster-racing-forum/75082-lightweight-flywheel-bad-idea.html
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Old 11-11-2020, 01:12 PM   #9
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Oh sorry for my late repsons, thanks all for the good input!

It looks like the flywheel I was offered has gone so I need to find something else. A lot of talk about the Aasco alu-wheel. I also realize that I want a sprung clutch, to mitigate the ratteling. This car is mainly a street car but I want it to be competetive at the track too.

So, if I would go with the Aasco, do anyone know a sprung clutch that would fit? My car is the 986s 2003.

Also a question to yoou gues who responded about lifting heigt, the 20", do you mean the total clearance so that 20" jacks would be enough? Or do I need to lift it 20" higher than how it stands with the wheels on? Stupid questions I guess.

I know that itīs an increased risk, but wtf..
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Old 11-11-2020, 02:30 PM   #10
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Quote:
Originally Posted by Robert986 View Post
Oh sorry for my late repsons, thanks all for the good input!

It looks like the flywheel I was offered has gone so I need to find something else. A lot of talk about the Aasco alu-wheel. I also realize that I want a sprung clutch, to mitigate the ratteling. This car is mainly a street car but I want it to be competetive at the track too.

So, if I would go with the Aasco, do anyone know a sprung clutch that would fit? My car is the 986s 2003.

Also a question to yoou gues who responded about lifting heigt, the 20", do you mean the total clearance so that 20" jacks would be enough? Or do I need to lift it 20" higher than how it stands with the wheels on? Stupid questions I guess.

I know that itīs an increased risk, but wtf..
Do your best to ignore anyone who says there are documented cases of failed crankshafts due to lwfw. Everyone always says this, but when pressed to provide said documentation, it invariably comes back to "Jake Raby says..... blah blah blah". He has "documented" ONE such case, with untold countless other extreme modifications done to the motor, yet le laid blame on the LWFW. Of course he did...

JFP on this forum has also said he's seen several over his years. I respect JFP immensely, and so I believe him. but they aren't "documented" so that we can look at what the circumstances were surrounding the failure. At that point I have to chalk those up to the same ethereal whispers of something.

On the other hand, there are literally HUNDREDS of documented installations with nary a problem. Including my own.

FWIW: I did not bother with a damped pulley, as that negates to some extent the reduction of weight I just did on the flywheel. I'm running a lightweight alu underdrive pulley. I DID however have my new pressure-plate balanced with the Aasco flywheel. Both were "close" from the factory, but not exact.
Use the Sachs Stage 3 clutch. And expect to hear the gear-lash anyway, when the trans is warm.

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Old 11-12-2020, 12:02 PM   #11
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Now that I've got a little more time, I thought I'd give you a little more of a complete view on the LWFW.

Most of this debate centers around what the actual purpose of the flywheel is on this motor. On many motors, the flywheel acts as an external balancer. You balance it with the reciprocating assembly to offset the imbalance inherent in the reciprocating assembly. When the flywheel is replaced with a flexplate (in the case of an automatic trans, for instance) then a balancer is used on the front of the crank.

This is NOT the same as a harmonic damper. (By the way; we're damping harmonics with a damper; we are NOT dampening harmonics with a dampener. )

A harmonic damper is simply absorbing shocks which tend to become vibrations. A harmonic begins with an event and then it "oscillates" at a wavelength which tends to feed itself, increasing dynamically as it travels the length of the crankshaft. A damper absorbs that oscillation / vibration / harmonic. But here's the deal (Biden reference haha) an internally balanced motor like the M96 has very few opportunities for that harmonic to occur, and if it does, it's absorbed in the gear-pack pretty effectively. Maybe you could have an issue if you like sustained high-revs in neutral.... The Dual-Mass flywheel is neutrally-balanced (such as a dual-mass unit CAN be balanced). IF you neutral-balance your LWFW, then your motor remains balanced.

So everyone who tells you you need to "dampen" the motor if you remove the DMFW flywheel; hand them a spray-bottle and tell them to have at it.

Quote:
Originally Posted by Robert986 View Post
Oh sorry for my late repsons, thanks all for the good input!

It looks like the flywheel I was offered has gone so I need to find something else. A lot of talk about the Aasco alu-wheel. I also realize that I want a sprung clutch, to mitigate the ratteling. This car is mainly a street car but I want it to be competetive at the track too.

So, if I would go with the Aasco, do anyone know a sprung clutch that would fit? My car is the 986s 2003.

Also a question to yoou gues who responded about lifting heigt, the 20", do you mean the total clearance so that 20" jacks would be enough? Or do I need to lift it 20" higher than how it stands with the wheels on? Stupid questions I guess.

I know that itīs an increased risk, but wtf..

Last edited by maytag; 11-12-2020 at 12:04 PM.
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Old 11-12-2020, 05:24 PM   #12
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Maytag throws it down ... Don't believe the hype.

I'm just one data point with a seven year old Aasco flywheel/clutch combo in a 2.5 race car running 10 - 20 days a year.

No issues, except I think I now no why my seven year old clutch slips a bit when it gets hot. Age!

Glad I checked my notes.
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Old 11-17-2020, 09:05 AM   #13
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Originally Posted by Hasbro View Post
Not sure what lump the op has but I believe there is a thread on this forum where Jack Raby said the 2.5 is pretty much ok at handling the resulting harmonics from a lwfw, whereas the others required more balancing attention. Anyone have opinions about that?
The longer the engine stroke the more stress load on the engine parts, & greater need for the parts to be balanced.
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Old 11-17-2020, 11:03 AM   #14
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The longer the engine stroke the more stress load on the engine parts, & greater need for the parts to be balanced.
which balancing is done internally... not by a dual-mass-flywheel. how you gonna balance with a mass that isn't always in the same place relative to the crank??
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Old 09-22-2021, 02:46 PM   #15
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What independent information exists on the RSS damped underdrive pulley and its merits?
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Old 09-26-2021, 12:37 PM   #16
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What independent information exists on the RSS damped underdrive pulley and its merits?
I've never found any negative experience with the UDP.
DO IT. You'll be glad you did.
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Old 09-26-2021, 05:44 PM   #17
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I think he's asking about the dampening effect, used specifically in conjunction with light weight single mass flywheels. I don't know anyone who has specifically installed this in a 986, but but the theory is sound. Many engines use the crank pulley as the harmonic damper, I don't see any reason why this wouldn't be a good insurance policy if going that route.

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Old 10-03-2021, 02:01 PM   #18
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Yes, correct. I was after the damping function performance. The dual mass does some of this correct? Anyway it would seem this added protection....very pricey at that

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