Dual mass flywheel balancing

[spongebob]

I have the really irritating vibration at 3000 rpm which many boxsters are suffering from.
Motor mount replacement,new flywheel etc are some of the steps taken to fix this.
But maybe the flywheels are not perfectly balanced when new as there are a lot of springs and grease inside this construction.
Could it be an idea to have it balanced in a good workshop? I sometimes doubt the standards Porsche used to build our engines.
Or any other ideas to solve this without going the Raby way with a total rebuild engine?

[Cloudsurfer]

Well, in an ideal world, you would balance the rotating assembly, which includes the flywheel, which can only be done while building an engine. Supposedly Porsche does this to every new motor that leaves the factory.

You can balance the flywheel and clutch setup off the motor. As to the engine internals, most any German build motor is pretty damn good on tolerances. Not perfect, and you can do better, but pretty damn good.

Any good flywheel that you would buy should come balanced. As to your dual mass unit, it is entirely plausible that it is worn. The two masses are held together with an elastomeric coupling, which can weaken or fail over time. If you're doing a clutch job, you'll want to change the flywheel anyway, as you can't reliably re-surface a dual mass unit.

If it were my car, and you have enough miles to warrant a clutch and/or just want to get in there and remedy your IMS bearing, I would pull the gearbox, update your IMS bearing, change the RMS seal, and do a clutch job with a new flywheel, balancing the clutch/ flywheel assembly before installing it.

[spongebob]

I did my clutch/flywheel three years ago and thought that it should cure the imbalance or resonace. But I never balanced the clutch together with the DMF.
Maybe that could make it better.
When I took the old DMF apart there where a lot of long springs and also grease that I guess can move around and cause vibrations. No elastomer which I thought there should be.
Another idea is to go lightweight but there seems to be many negative effects if I chose that way

[Cloudsurfer]

Eh, plenty of us are running light flywheels, I love mine. Some would argue that you should only run a LWF if it is balanced to the engine, and on a track car I would agree. What is critical, is that you change the rigid clutch disc for a sprung unit.

You should also be able to retrofit the 3.8 engine's harmonic balancer to the pulley side of the motor to further smooth things out.

[spongebob]

Hmm, harmonic balancer.
Is that a direct bolt on?
Also, how much more gear clatter do you have with a lwf?

[spongebob]

[Cloudsurfer]

Cool pic. As far as I know, the harmonic balancer from a 3.8 is a direct bolt on to any M96 motor, but I have not tried this yet.

[rob76turbo]

Originally Posted by bmwm750

Eh, plenty of us are running light flywheels, I love mine. Some would argue that you should only run a LWF if it is balanced to the engine, and on a track car I would agree. What is critical, is that you change the rigid clutch disc for a sprung unit.

You should also be able to retrofit the 3.8 engine's harmonic balancer to the pulley side of the motor to further smooth things out.

How do you balance the LWFW to the engine? I am thinking of going this route, but will be doing the R&R myself (along with IMS, RMS, trany mounts, ETC).

[jaykay]

Just curious as to whether anybody knows whether a light fly wheel could mitigate crankshaft and RMS damage by reducing the overhung weight at the back of the crankshaft. I would think the DMFW at 40 lbs, slightly unbalanced, on a slightly untrue crank could cause undue crank shaft deflection resulting in RMS damage and leaks. I would think by the time you have an RMS leak you already have engine damage.

I was thinking of a LWFW just to prevent this scenario but I am just learning about all the negatives associated with it. I have a very low mileage engine (m96) that I would like to make reliable.

What flywheel would I use to be safe? Do I need a clutch to go along with it? It is not a race car so I would like to keep it as streetable as possible. What are the risks? Will a dynamic balance problem be caused?

Thanks,

jaykay

[Cloudsurfer]

Unfortunately, to balance the flywheel to the rotating assembly the motor needs to be torn down, so that's only an option during an engine build.

Hypothetically, some argue that the use of a LWF will make the RMS seal more reliable. Others contend that the LWF has it's own set of downsides.

If it's a stock, street car, you can get a stock equivalent sprung centered clutch. Always use a new new pressure plate.

[BYprodriver]

Originally Posted by bmwm750

Unfortunately, to balance the flywheel to the rotating assembly the motor needs to be torn down, so that's only an option during an engine build.

Hypothetically, some argue that the use of a LWF will make the RMS seal more reliable. Others contend that the LWF has it's own set of downsides.

If it's a stock, street car, you can get a stock equivalent sprung centered clutch. Always use a new new pressure plate.

I would think the besy solution would be a lightweight aluminum pressure plate. I have never seen one advertised or even discussed. Anyone else heard anything??

[Jake Raby]

A LW pressure plate is being tested now with 3 different stages of aggressiveness.

[BYprodriver]

Nice to hear, I look forward to that!

[Cloudsurfer]

Now that sounds interesting...

What vendor have you sourced a LW pressure plate from?