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996lee
Montreal
Joined: 26 Aug 2014
Posts: 608
Location: South Wales/Nottingham
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 Posted: Thu Aug 03, 2017 7:20 pm Post subject: Which Single mass flywheel with which clutch?
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Hi guys
My clutch is on its way out so thought I'd take the opportunity to get a bit more performance out of the old girl so planning to put a single mass fly in and possibly an updated clutch if that's recommended over a standard clutch?
So which clutch and flywheel combo works best for a fast road set up?
As always your advice is much appreciated
So far from reading aasco seems to be the result that keeps coming up and cheapest I've found it was 693 at the porsche shop
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2001 Carrera 4 aero all the way!!
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Marky911
Imola
Joined: 04 Jun 2009
Posts: 853
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| Posted: Thu Aug 03, 2017 8:42 pm Post subject:
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Watching with interest Lee as my car is going for IMS seal flipped open hence new clutch, in a month or so.
It's all a bit vague re the single mass flywheels. Apparently they have to be balanced with the clutch as one unit to stop vibrations putting strain on your crankshaft and bearings, which I'm sure you already know.
It's finding out who does it etc and if they'll do it with the new clutch I already have here or if they insist on supplying the clutch and flywheel.
I'm still wary about it to be honest. These engines are so hitty missy that introducing new stresses could be opening a can of worms. I also only like to do easily reversible mods to my cars, however the difference in feel a LW flywheel makes is great. I loved it on my GT3.
Maybe Harv, Popop or the other engine guys may know. I did touch on it on Kens (9e) project car thread but he didn't really answer to say he'd balanced it all. That could mean he didn't do that. I don't know.
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996lee
Montreal
Joined: 26 Aug 2014
Posts: 608
Location: South Wales/Nottingham
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| Posted: Thu Aug 03, 2017 10:16 pm Post subject:
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I have actually had quotes from Ken and also rpm technic
But wanted to price up buying the parts myself
And then get quotes from Indies to fit them as a second option
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2001 Carrera 4 aero all the way!!
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Marky911
Imola
Joined: 04 Jun 2009
Posts: 853
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| Posted: Thu Aug 03, 2017 10:40 pm Post subject:
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Ah right. So do they balance the parts then or just bolt them on?
This is the part I know nothing about.
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Harv
Suzuka
Joined: 18 Sep 2014
Posts: 1041
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| Posted: Fri Aug 04, 2017 12:33 am Post subject:
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I can point you in the direction of TTV racing's single mass lightweight flywheels via coordsport which is where I got mine, made in the UK and I have heard it's the same unit rpmtech fit to their cars.
This works with the oem clutch kit but you will then need a different sprung centred friction disc as the oem one is solid, I have found a supplier for that also in techniclutch.
For the best result you should balance the front pulley, crank, flywheel and clutch cover plate but you can just have the clutch and flywheel checked. My take is it will reduce stress on the crank as you are loosing a very heavy old dual mass flywheel which have dubious balance out of the box let alone after 75k and nicely reduce the weight/stress induced on the those last main crank bearing shells (a known design flaw).
True it's not a five min job to swap back agin if you decide you dont like it but no problem if you can live with a little chattering at idle, I think you stand to gain more than you'll loose.
Hope this helps
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996lee
Montreal
Joined: 26 Aug 2014
Posts: 608
Location: South Wales/Nottingham
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| Posted: Fri Aug 04, 2017 9:42 am Post subject:
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Hi harv that's right it is the type rpm use
Theirs was 828 quid with the sprung friction plate
@marky 911 to be honest non of them has actually mentioned balancing
That's not to say they don't but it's all info I want before commiting
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2001 Carrera 4 aero all the way!!
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Harv
Suzuka
Joined: 18 Sep 2014
Posts: 1041
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| Posted: Fri Aug 04, 2017 9:46 am Post subject:
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Use Richard at Coordsport, about £385 when I purchase mine, the centre disc is £110 from the place mentioned who buy up lots of un-used stock but you'll need a clutch cover plate and release bearing anyway so try them for the lot.
Out the box I'm convinced it's better balanced than a DMFW but put it in somewhere and have it checked.
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996lee
Montreal
Joined: 26 Aug 2014
Posts: 608
Location: South Wales/Nottingham
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| Posted: Fri Aug 04, 2017 12:58 pm Post subject:
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I'll admit I don't really understand the balancing bit
As I just assumed the flywheel was balanced on a computer similar to as per what your wheel is when that's balanced
So no idea how it's balanced with the crank etc
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2001 Carrera 4 aero all the way!!
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Marky911
Imola
Joined: 04 Jun 2009
Posts: 853
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| Posted: Fri Aug 04, 2017 4:32 pm Post subject:
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That's the bit I don't understand either Lee. 
Even though I'm a precision engineer by trade and have fitted clutches/flywheels to road cars and track cars for my hobby over the years, I can't picture how they do it.
The prices seem good though. I expected it to cost the thick end of £1000.
I may be pushing it to gather the parts and get them balanced as my car is due at my Indy in a few weeks time.
I may knock it onto next years list as he only charges £250 to remove box, clutch and flywheel (and change RMS/IMS if necessary), then refit. So it's no biggie to have it done next time.
Interested to see how you get on though Lee as it's definitely something I want to do.
Great info Harv, the best info I've seen on the topic to be honest. Everyone is a bit vague usually.
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911munKy
Spa-Francorchamps
Joined: 26 Nov 2014
Posts: 314
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996lee
Montreal
Joined: 26 Aug 2014
Posts: 608
Location: South Wales/Nottingham
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| Posted: Mon Aug 07, 2017 2:56 pm Post subject:
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Needed to get the ball rolling as my summer holidays are nearly over so purchased rpms flywhèel along with sprung friction plate
Will report back with my thoughts once it's all fitted
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2001 Carrera 4 aero all the way!!
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Marky911
Imola
Joined: 04 Jun 2009
Posts: 853
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| Posted: Mon Aug 07, 2017 3:57 pm Post subject:
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Nice one Lee. I'm sure you'll love it.
I must admit I knew I'd read negatives about it a while back and that post of 911munkys has refreshed my memory. Good link munky, thanks.
I think I'll leave it for this year. If I was having an engine built and could have the crank, LWFW and clutch all balanced then I would, although that still doesn't sort out these "harmonics" people go on about.
I'll revisit my flywheel once the rest of the car is as I want it, but with wheels and calipers to refurb, Aerokit to fit etc, I don't want to be throwing in a part that could cause me trouble. There are cars running them without issue but there's no smoke without fire, so I'll look into it again next year.
Report back with your thoughts Lee. Like I say you'll love the way the car revs and picks up.
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Jamesx19
Monza
Joined: 10 Jul 2015
Posts: 183
Location: Brighton
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| Posted: Wed Aug 09, 2017 2:49 pm Post subject:
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I stand to be corrected, but.....
The point about balancing is: The flywheel will be balanced by the manufacturer before it leaves the factory, as will the clutch cover, and of course when the engine was built the crankshaft etc was balanced too.
BUT - All these components were all balanced separately and to varying degrees of tolerance. ie to within 1 gram or 0.25 grams, or 5 grams? Then you bolt them all together which means that the chance of the rotating assembly now being in balance (Or within tolerance of what is considered balanced) is tiny. Chaos theory comes to mind here!
So, what do you do?
If your building your engine yourself, you can get the whole rotating assembly balanced from front pulley, crank, flywheel and clutch cover. Rods balanced end to end, and pistons matched etc. Plus you can get a real expert like David Brown at Swaymar's to do it (Credit to Harv - thanks) to within 0.25 gram. Beautiful and perfect and lovely.
If your fitting to an existing engine, you can get the flywheel and clutch cover balanced to each other, but they will still not be balanced to the rest of the crank etc. So not perfect. What tolerance is it balanced to within, or how much is it out of balance?
So is a Lightened and balanced Single Mass flywheel better than a Dual Mass flywheel? Is the Dual Mass flywheel likely to be worse, or better in this regard? Well you do your research, listen to the good advice, pay your money and take your choice!
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1998 C2 Manual
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Marky911
Imola
Joined: 04 Jun 2009
Posts: 853
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| Posted: Wed Aug 09, 2017 4:03 pm Post subject:
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Pretty much that James....
But there's one more point that no amount of balancing will solve...
Harmonics.
After reading the above thread and many others most 996 engine builders seem to concur that the dual mass flywheel acts a big damper for engine harmonics and removing this for a single mass item leaves all these to transfer to the crank.
Forged balanced cranks can handle this but sintered cranks (which a 996 has) cannot, hence stories of snapped crankshafts on some engines.
I don't believe the likes of RPM would just bolt them on ignoring this, so on the one hand I still think some of it is hot air. On the other hand I can understand the principal and after owning a GT3 which sounded bloody awful at tickover
(In neutral with clutch out) I can see the argument for the damping effect of a DMFW.
I'm going to fit my standard gear next month then look into it again in a years time, if I can find out some concrete info by then.
Last edited by Marky911 on Wed Aug 09, 2017 8:50 pm; edited 1 time in total
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Jamesx19
Monza
Joined: 10 Jul 2015
Posts: 183
Location: Brighton
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| Posted: Wed Aug 09, 2017 5:22 pm Post subject:
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Yep, +1.
I did that last month. The bottom line was I felt I had more to lose with the LWFW through unreliability, (Broken crank, potential extra strain on the valve operating chains / IMS, and gearbox internals) than I had to gain with a freer revving engine.
If I was doing what Harv. is doing though, no question I'd fit the lightweight single mass item.
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1998 C2 Manual
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Harv
Suzuka
Joined: 18 Sep 2014
Posts: 1041
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| Posted: Wed Aug 09, 2017 6:45 pm Post subject:
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Good work James, you have it nailed in that post
I'm certain that rpm won't just be bolting these on and haven't heard any reports of their cars cranks failing.
Who knows what the DMFW comes with out of the box  perhaps by their nature they don't need to be too well balanced as they simply smooth it all out until the springs inside fail. David gave me some good figures of how a few grams adds up when you move that outside the centre line of the crank and spin it at 6500 rpm. A bit like pulling G in an aircraft and the multiple times things weigh (for comparison).
Flip side, Infrasilver's crank broke when the dual mass flywheel failed (can and does happen and that's why they say change it when the clutch is at end of life)
Pays your money and takes your choice (or should that be chance)
I'd love to see some knock sensor graphs for our engines (back to back for both flywheels) as by design I thought the flat 6 was inherently well balanced.
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996lee
Montreal
Joined: 26 Aug 2014
Posts: 608
Location: South Wales/Nottingham
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| Posted: Wed Aug 09, 2017 7:52 pm Post subject:
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I asked rpm if they balance them when fitting and the answer was no they don't and have never had any faults
_________________
2001 Carrera 4 aero all the way!!
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Harv
Suzuka
Joined: 18 Sep 2014
Posts: 1041
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| Posted: Wed Aug 09, 2017 10:32 pm Post subject:
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Thanks for clarifying that, should inspire confidence in those going for it.
I don't recall the out of the box balance figure for the TTV smfw but certainly you can improve it significantly by selecting a good machine shop.
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996lee
Montreal
Joined: 26 Aug 2014
Posts: 608
Location: South Wales/Nottingham
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| Posted: Wed Aug 16, 2017 4:46 pm Post subject:
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Picked the car up and took her for a long drive and im very impressed with how much more urgent it feels
It has added to the nvh levels but i don't mind that at all think I'll change my driving style a little as when pootling along in traffic and taking a slow corner in a higher gear than i should the vibration is a bit much
Chatter wise I sat there with it idling and thought "there is non" however on getting out and having a listen from outside it does sound like a diesel (a bit) luckily the sports exhaust on idle drowns most of it out
But so far so good 
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2001 Carrera 4 aero all the way!!
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Harv
Suzuka
Joined: 18 Sep 2014
Posts: 1041
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| Posted: Wed Aug 16, 2017 5:00 pm Post subject:
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Excellent feedback and glad you went for it.
Indeed you'll adjust to it and so does everyone that gets into a GT3, don't get many complaining about the NVH of those and everyone wants one 
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