Competition light weight clutch.

Does any one on this forum have any usefull information about light weight competition clutches. I would be intrested if they are good or bad for a road going car. What are their advantages, and disadvantages. Thanks.

Lightweight flywheels will allow your car to rev quicker, far less mass to get moving, so the car just feels like it wants to rev quicker and it does. Negatives? Noisier, especially when at idle. Harder to balance as pulling away, need to give it a bit of wellie. Needs to be properly balanced, and that is not easy. Cars that come from the factory with one tend to be balanced with the engine out and heads off. Many can give you some vibrations at certain rev ranges because they are not balanced. Stress. Because of this imbalance you are putting immense torque on the crankshaft and the bearings. If you look at the threads where people have vibrations above 3500rpm or similar, many have run lightweight flywheels and probably had them fitted without them being balanced. They are great if done right.

I'd very much agree with the above assessment. As a recent personal testimony though, I had a lightweight flywheel installed in my 997.2 early last year. And in overall terms I'm really impressed with it and the improvement in driving experience, and I'd never go back to a standard set-up. So do recommend it if all else is ideal. My assessment re the balancing of the crank / flywheel is that if I had an M96 / M97 engine (not the Mezger engines though) I would not have gone with a lightweight flywheel without crank balancing, as the main bearings are not as strong / optimally laid out as they are in the 9A1 engines (or the Mezger's). I realise this is an engine strip job to achieve though, so is significant. Also, my Indy who installed mine would also say ideally your gearbox should be rebuilt too if it has any significant mileage on it, as driveline slop and bearing end play may cause too much gearbox chatter / noise. Mine was rebuilt when I put my LWFW in as the synch had gone on 2nd gear, so is now very quiet.

Lightweight clutch or lightweight flywheel ? (or both) ? Lightweight clutches are normally paddle type clutches, which depending on the friction material used (organic or cera-metallic) are either totally unsuitable for road use (cera-metallic) or acceptable (organic). Most paddle clutches (but not all) will have unsprung driven/centre plates, which means they’re noisier, transmit more vibration and are “snatchy” when they reach their bite point. Personally I wouldn’t advise using them in a roadcar. Lightweight flywheels are another can of worms altogether. RPM Technik seem to fit them to both M96/M97 engined cars and the later DFi engined cars without issues. I’ve driven a 997.2 3.8 S fitted with an RPMT LWT flywheel and was hugely impressed with the improvement in throttle response. Though it has to be said the DFi engines are generally more responsive, revvy/rev hungry than their M96/M97 counterparts. This is quoted from a thread running on Rennlist regarding this very topic : “It's not really about the balance of the flywheel, the flywheel can be in perfect balance and it doesn't make any difference in the "risk" of damage from harmonic vibration, it is the "lack of dampening" that can cause unwanted damage.. All engine designs have harmonic vibrations, the flat six is one is the best ( inline-4 is the worst)...but our factory pistons are only weight matched to within 3 grams, I have seen factory rods from different engines be as much as 15 grams difference and is why the factory only sells the rods in a matched set...( and they are expensive)...When doing a race engine mose shops ballance the rods and pistons to within 1 gram or .5 grams..This reduces harmonic vibrations a lot... All materials/objects have a frequency/Hz at which they resonate...Like a Crystal glass will resonate at 1046.502Hz ( high C note ). If a Soprano singer hits the high C note/1046.502Hz for a period of time, any Crystal glass within range will began to resonate and if sustained will shatter... The combustion on each cylinder causes the crankshaft to flex and causes a vibration...the weight of the pistons and rods also causes a vibration , There are many different harmonic vibrations in an ICE at different frequencies/amplitude and they all will vary in frequency/amplitude with RPM's ....The dual mass flywheels and/or harmonic balancers dampens the amplitude of the harmonic vibrations or change the frequency of the harmonic vibrations so that they do not resonate on a particular part ( crankshaft)... Not using a dual mass flywheel or harmonic balancer does not mean instant failure of our crankshafts, our crankshafts are very high quality ductile steel that is strong but also flexible enough to withstand flexing and vibrations with a very hard thin layer of nitriding on the bearing journals to resist wear. The resonance frequency of our crankshafts can be driven through many many times without damage because the crankshaft is flexable/ductile enough to handle it, but if the resonance frequency is a high enough amplitude and/or is sustained long enough the crankshaft will crack like a Crystal glass when the Opera singer is hitting the high C note .. I didn't want to go too far down the Technical rabbit hole, or give long winded details of my dealings with harmonic vibrations on a high buzzing 12k rpm in-line 4cyl 2.0L 525HP that would snap the flywheel bolts off at 12K rpm because the crankshaft was NOT flexable/ductile enough to absorb the flexing/vibrations of the harmonics...( the crankshaft was actually too strong/stiff to absorb the flexing and harmonic vibrations, so they transmitted to the flywheel bolts and snapped them like glass, even grade 12 loctited and safety wired with 1/2" dial pins inbetween). I even bought one of the $400 Fluidampr's when they first came out in the 80's and destroyed it at 12k rpm in first run.. I just wanted to give some Technical/common sense overview facts of why there is such different opinions on the subject ( this IS a technical forum), It doesn't matter to me which flywheel you use or why. You just sounded a little apprehensive of the LWFW and the noise it causes, justifiably.” Be aware of the risks involved, then decide if the benefits outweighs those risks...

Oh "Slippydiff", you have given me plenty of information to go away, and consider my next move. To my advantage, the engine is going to be removed and rebuilt into a 3.9, this puts me into a nice position to possibly have it balanced, it was something i was thinking of doing anyhow as experiance in the past with balanced engines puts me in that way of thinking. So, i shall think a little more on the subject, ask my engine rebuilders what they think and mull it over some more. Thanks to the others who also added their input it was very much appreciated.

Yeah, if you are having the engine rebuilt then it is well worth talking to them. I love LWFs myself, but even though I am having a new flywheel and clutch fitted this week I bottled out of having a lightweight one fitted.

Why ?. I would be interested in your reply. You say you love them, what experiance do you have of them ?

Remember the 996T uses a DMF with a solid clutch. If you fit a LWFW you'll need a sprung centre. The mistake people make is using a solid centre without the give of the DMF. There's nothing wrong with ceremetallic material, what makes them more grabby are puks, less puks, more grab. I've got a full face ceremetallic solid centre on the DMF for road duties, full face gives better road use than a puk clutch. I had one on a previous car and it felt like stock. A lightweight clutch is smaller. I've got a 7.25 on my escort, so less rotating mass.

If you're rebuilding it anyway it'd be a no brainer to me to get the crank and lightweight flywheel balanced too. A 3.9 with a lightweight flywheel would be awesome I'm sure! I agree with the last comment on here too, if you're going LWFW then you'll need a sprung clutch plate rather than solid. I went with the TTV Racing flywheel and Sachs clutch and cover on mine.

Because all the cars I have driven with them just feel so eager to rev, they rev up quicker and also the rpms drop quicker too. It is difficult to describe, but there is something about them that you will get straight away. I don't really like the way you pull away in first with them, and if you drive in traffic at all it is horrible, but I would still live with it. The reason I am not putting one in is my car is in for judder around 4000rpm at the moment, new clutch, flywheel, EPS IMS, transmission mount and hopefully that sorts it. But I don't think it is sensible to put a LWF on a car that is 22 years old on the original crankshaft and bearing. My crankshaft has 0,02mm of deviation, Porsche tolerance is 0,04mm, so it is OK, but the bearing could be just a smidge out through wear and the last thing I want is any more vibrations that a dual mass flywheel tends to hide.

Thanks for the reply, your contribution is helpfull.

This thread has taught me many different things about the subject of light weight clutches and flywheels. Even now, i am now where near making a decision. Its not because i am indecisive, but most of the replys point me in the direction of going down the road of getting one, but a sprung flywheel being important in the choice. I spoke to the man at hartech who will be doing the machining and supply of the necessary parts, and he said no dont go down that road. Reason being Porsche made a really nice car for road use, why spoil it by fitting a clutch that lets the drive train spoil a pleasant drive, and then to top it off, he said getting it all balanced was a waist of money as the components of a Porsche engine were far better than most manufacturers. When your told that, from a person who has much more experience , you take on board what is said, but the last few reply's point you in the direction of sprung flywheel's to overcome the issue of noise being transmitted back through the drive train. A good nights sleep and think of my next step me thinks.

Mark, I was waiting to see if you got the Hartech negatives towards lightweight flywheels, and it seems you have! I can't really understand why they hold those views frankly, and if you read their actual experiences they seem to make more comments on automatic cars than with manuals. Though that might just be the biases I've read where they've commented on forum posts, rather than their post workshop experiences. The "spoiled drivetrain" comment from them makes no sense at all to me, and I do wonder what their actual lightweight flywheel experience really is on cars they have rebuilt / converted. I do know they've been asking for a manual car with a DFI engine for some time, to complement their PDK experience. Ditto with their comments on balancing, given the additional costs are so negligible I can't see any downsides. I think we all have our own preferences and criteria of what a good road car is. And certainly the primary use of a car will determine whether much slow traffic is likely to be encountered. But for me, given now many thousands of miles in cars with a lightweight flywheel I've driven, the very minor inconveniences are very much outweighed by the benefits. In Porsche world that's with 993, 996 GT3 and 997's only, so with either Mezger or DFI engines. That does include a fair chunk of city driving too, though not as a daily / commute. Are you able to try anyone's car out that has a LWFW on it before you start reassembling your own car and need to make a decision? If you're located in near to Surrey or the home counties you'd be very welcome to try my car. Its obviously not a 996 though, so won't be a direct comparison of what you'll have but will give you some idea if the negatives would irritate you. Interesting thread though! Good luck on your deliberations. :thumbs:

Thanks for your reply. Firstly, do you have a sprung flywheel, as i did send an email to the company in a previous reply on here, they dont do one for my 996 ,4s, so that has gone know where? I live in Suffolk, so not the end of the world for me to take you up on your much appreciated offer. But that thought did cross my mind in the last 48 hours, so heres the answer. I need to be very sure of my choice, because, it must still be as enjoyable as a normal clutch. This is only a road going car, and living out here, in the country side, most of my driving is done in fast moving traffic, with a little slow moving occasionaly. Hopefully the answer to my first question is yes, and I find out where I can get a sprung light weight flywheel from. I look forward to your reply.

When I said sprung centre, I was referring to the clutch. So you need a sprung clutch with a solid flywheel (LWFW are solid) DMF is sprung, so you use a solid clutch with a Dual Mass Flywheel. A solid clutch with a solid flywheel will be horrible on the road, which is a mistake often made, I think because people specify a standard clutch, which is a solid disk due to the DMF.