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Lightweight flywheel (RPM Technik - CSR)

I had a go in the car with the flywheel.

The good: didn't make it any more difficult to drive. In fact, the free-spinning nature made it easy to blip the throttle on a downchange (if so inclined) and drive quite smoothly.

The bad: the noise. It sounds awful. Like something is about to rattle itself loose and fall out of the car when it's sitting at idle. It's fine when the clutch is in though.

Question: it's also noisy at times when underway. It's hard to describe the sound but it groans or grumbles when engaging the clutch at low revs (like setting off in second, for example) or when accelerating hard (only for a moment)

Is this normal?
 
I'm by no means an expert, but I'd wager it's not normal. I recently drove a 996 C2 with a LWFW, clutch & LSD & didn't notice any significant increase in NVH over my own C2 without these drive train mod's.

Perhaps the car you drove needs refreshed transmission &/or engine mounts OR perhaps it has the original powerflex transmission mount inserts which several people have reported added NVH.
Might be worth enquiring about that cars history to see if these were done when the LWFW was fitted.
 
On my turbo there was definately a bit more chatter at idle until the clutch was pressed. When I changed to RSS engine mounts this largely went away. It certainly shouldn't sound like a bag of spanners.

MC
 
Interesting.

According to the history, the flywheel was fitted as part of a clutch service as a small additional extra by RPM. No mounts were done at the time.

It's really quite a bit noisier at idle than stock. It sounds almost like the chatter from a diesel engine if that makes sense.

Here are a couple of vide examples that came close:

This is a 996 GT3, but sounded pretty similar: https://www.youtube.com/watch?v=aMIZAm9qWKw

And this one's on a Boxster:
https://www.youtube.com/watch?v=vAVb_vPUHaE

It's mostly worrying accelerating from low revs as that's when it makes quite a pronounced sound to start with and then goes away.

It's a tough call this one...
 
That boxster sounds like the release fork is loose. Maybe there is something in the way it goes back together that means the clutch assembly is fractionally shorter with a LWFW, meaning the release fork mechanism has slop in it that allows it to rattle. Just a thought.

I don't subscribe to the school of thought that a solid rather than standard flywheel will always be rattlier and it should just be put up with. Plenty of cars out there have a solid flywheel and a sprung centre plate and manage to not rattle. I reckon that the way it goes together has a lot to do with it, and better selected parts may well improve it.
 
sp1ke said:
I'm by no means an expert, but I'd wager it's not normal. I recently drove a 996 C2 with a LWFW, clutch & LSD & didn't notice any significant increase in NVH over my own C2 without these drive train mod's..
Click to expand...

This ^

I have just had mine back with a LWFW, (sprung clutch & performance pressure plate), granted it was balanced to the crank, but there is barely any increase in NVH, a tiny bit at tick over but thats only really noticeable because I am looking for it.
 
Interesting points about how it's balanced and fitted.

There is a clear and obvious increase in noise and vibration over stock in this car's case.

My thinking is to get the flywheel taken out as it doesn't sound like it's good for the drivetrain. It hasn't been in there for more than a few thousand miles, so probably wouldn't have cause any trouble, would it?
 
If you're unsure about risk of damage, then it might be worth holding out for another car.

Having said that if you're dead set on this one, then before you consider ripping out the LWFW, consider replacing the engine mounts & perhaps add the newer powerflex gearbox insert to see if they help to cure the NVH.
This may be a cheaper solution & if the mounts haven't been done before, they probably need doing anyway, so it's likely still money well spent even if it doesn't cure the noise.
FWIW I recently opted for the 993RS mounts from type911shop.co.uk (product # 9791). They were reasonably priced & made a noticeable difference.

You can still replace the LWFW afterwards if you're not happy. At which point it may be worth replacing the clutch & gearbox mount while you're at it.
 
The LWFW should have a sprung disk, the dual mass one will have an unsprung disk. So if you are planning on swapping over then at least budget for a clutch disk to go with the flywheel.

MC
 
Thanks for all the advice. I've had quotes for replacement with a dual mass and it 'ain't cheap. So maybe the other options you mentioned like the engine mounts and gearbox work make sense as I doubt that would cost (a fair bit) more than a grand.

Do RSS mounts affect ride quality? I spoke with another guy on here who mentioned how it improves shift feel, but I don't want to make things harder as the stock 996 4S set up is good for me.

I've been hunting for over 18 months and have had to suffer 3 failed PPIs, so I want to focus on this car as it's just right for me on paper.

I just don't want a component in there that will cause problems down the line, as I'm looking at this car as a long term keeper.
 
I had one fitted to my 993 and 997.1 without any issues .

Revs build and drop quicker, throttle more responsive and I would choose one again if I modified another car .

Definitely needs a sprung clutch plate and for me worked best with RSR engine mounts . To stiff and it did become intrusive .

It does chatter a little at idle until about 2000rpm and slightly more nvh but if installed properly not an issue for me .

No issues with stalling on the 997, occasionally did in the 993 but not often once I got used to it .
 
I run a powerflex gearbox mount in mine along with genuine Porsche RS engine mounts.

The former didn't make a great deal of difference, the latter did.

Engine mounts don't effect the ride per say, but stop the engine moving around, so stiffer mounts tighten up the handling.

Stiffer mounts can increase NVH, but it's a matter of taste and tolerance. - I find no issues with the Porsche RS items, nor the Powerflex gearbox mount for that matter.
 
I have fitted powerflex gearbox mount recently....what a change I like it a lot easy to do and cheap what not to like about it :) gear change is more smooth and easier also feel of my C4S way batter, now just waiting for engine mounts RS these should improve even more.
 
mine has some chatter at idle

whilst driving the only time i have any increased NVH is if ive let the revs drop too low
which will happen quicker as the revs drop quicker
i know above you said it didnt drive much different
but i definitely had to change my driving style a bit when i first had mine fitted
ie using higher revs and lower gears than i would have prior

can get a vid up of it at idle if you'd like?
 
A vid would be great 996lee.

Would definitely help to compare with the sound of the one I'm looking at as it seems that there are various opinions as to how much noise is tolerable.

Your experience sounds similar to my test drive - there was noise and some vibration when accelerating from low revs - around 2k in third, for example.

It didn't feel that much different to me since I usually drive using more revs anyway and don't really rely on low end torque. I've never owned a diesel or a petrol turbo, so years of driving cars where the power is at the top is probably what has done that to me.
 
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