cmoss

I have the lwf/rs clutch and I really like it. The engine does rev quicker, and a bit more hp is available, as the engine need not spin the extra weight. But there is more rattle, and requires a bit more gas on take off.

mborkow

cmoss is correct about the noise. the lwf makes more chatter than the dme; porsche created the dme to reduce the sound the lwf made...but the advantage in sound was at the expense of performance. getting the lwf is simply correcting a compromise that porsche never should have made, imo

Rezal

I don't understand how a LWF cuts unsprung weight since unsprung weight is related to your wheels, brake calipers & rotors and anything else that hangs off the shocks and springs (i.e. "unsprung").

What the LWF would do, however, is reduce rotational mass.

Ray may (sometimes?) be a little caustic but all he's saying is that it doesn't do anything for him. Your results may differ. Dunno about a "wrong opinion". It is afterall an opinion as opposed to a fact.

Some people jump on the mod band wagon without an understanding why things are done (i.e. more money than brains), or thinking that their needs are the same. I'm guilty of this too. I have a Big Red set-up when a set of dedicated track tires with race pads on stock OEM calipers would've been a more cost effective route for me.

As this thread originally started out, Jeff said that he doesn't track his car. With a brief experience driving a 993 with a racing flywheel and clutch (not sure what kind), I know that throttle modulation can be a real b**ch in stop-and-go traffic (aka LA freeways!).

Terry Adams

I had not considered the LWF/RS clutch mod until it became a "while we are in there" item during the recent top end rebuild. I should have driven another Rennlister's car with this mod before deciding, but I jumped on the bandwagon. Partly because of cost - $1500 in parts with no extra labor because we were in there already, versus about $2300 for an OEM clutch replacement alone. Partly because of reviews here. Partly because of my driving - not stuck in commute. I average about 80K miles on a clutch, so mine was only about half worn. But the original DMF was showing some play in the rubber part, causing rough idle. Now I have a slightly rough idle because of the LWF.

On balance, I am way more pleased with the faster rev spooling and clutch bite, than I am with the shifting rev drop and minor rattle. I urge anyone considering this mod to drive another's car first, as it is a matter of personal preference.

ibdavid

Terry, can I drive your car

Darin, please chime in here....

mborkow

for a very good explanation of a how the lwf works (and why i refered to it as unsprung): http://www.uucmotorwerks.com/flywhee...heel_works.htm
(very good read)

mborkow

if someone in the bay area wanted to try out an lwf i'd be willing to let them drive my car.

Rezal

I think using the phrase "unsprung weight" is misleading as almost all of the time, it refers to suspension components (ie lower unsprung weight = better suspension response due to lower inertia leading to more accurate tuning). While the link you sent was informative, no where does it use the term unsprung.

Reducing rotational mass is different and is what the article refers to as a "virtual" weight loss. This was something that Porsche touted a lot in the Carrera GT marketing material (ceramic clutch). Same reason why some cars such as the new 350Z use a carbon fiber drive shaft. Again due to the multiplicative benefits of reducing rotational mass, and not just straight weight which may be just mere grams.

mborkow

"While the link you sent was informative, no where does it use the term unsprung."

i stand corrected. in my mind i thought of it as unsprung because of the following quote: it must be remembered that the rate of acceleration on the engine internals is much greater that the rest of the car. This would then suggest that by lightening the flywheel, less power would be required to accelerate it and therefore more power would be available to push the car along.

the article, however, does not refer to it as unsprung, and i am sorry for the misinformation (i would go back and edit my posts, but then this conversation wouldn't make sense to anyone else :-)).

Texas993

Interesting string with great information, thanks guys.

dhicks

mborfkow...great info article, thanks.....I just know that even with eth chhhattttter I still love the LFW and the faster revs...but as somebody else says it is very much personal taste and will not be everybodies cup of tea! Driving one first si a great idea, wish I had, it would have put all teh doubts behind me before I did the conversion!

Terry Adams

David, you are welcome to try my car. Good opportunity for me to hear that exhaust of yours that the guys are raving about. Maybe too much for me. Well, for my neighbors.

FisterD

David, come drive my car........since you got your hands dirty on it! You can also hear my mufflers.
My (personal) observations,
Revs quicker.....yes, very responsive.
Noisier......yes..but definitely not a big issue.
If you don't give it a little extra gas from the get-go, it does make a little grumbling noise. But when you rev it a little more and release the clutch (which grabs hold like a pit bull on a poodle), man it's go time, and the car feels like it's ready to take off!

If you don't like extra noises, this mod may not be for you. If it is more performance you are after, I think it is a MUST!

mborkow

i haven't heard anyone who has this mod say a bad thing about it (i haven't even read a neutral review; everyone likes it...)

Marv

While I understand the physics of a low mass versus a higher mass flywheel, I am not sure of the real advantages for racing other than weight reduction. However, there must be advantages beyond the reduction in weight for driving. If memory serves, that weight difference is almost 20 lbs! maybe someone here can speak to the racing advantages.

That said, back to your specific question on what performance improvements can you expect. Here is another way to look at the problem. Consider the time it takes to rev the engine from idle to redline in neutral and when you have the car in gear.

The light weight flywheel will make a significant difference when in neutral, but nothing noticeable when in gear. The reason is that when in gear your engine must use a significant amount of torque to accelerate the car, which is much higher than the force required to rotate a flywheel. The ratio of those two explains why it takes so long to get the car up to redline when you are in gear.

The flywheel is actually a very small fraction compared to the amount of power required to move your car. If you cut the flywheel mass by 50% you are only taking a very small amount off the total equation.

So you will not notice a seat in the pants difference and even less so with the higher horse power of the Turbo.

However, it does make the experience of driving more fun to me to have a snappy engine. Just bear in mind that you trade off a few things with the lighter, single mass flywheel. Expect a little more gear box noise and the shifting may feel notchy depending on the extent of sychro wear.

Others have commented on the dead starts being a little more tricky. My 964 required a little more throttle and finesse to avoid PIO or stalling. Probably the same for the 993.

Marv