rk-d

I have a '98 C4S and I'm seriously considering installing the RS clutch and LWS. Current clutch feels strong, but I hear a rumble/rattle when I shut off the car and I have a sneaking suspicion my DMF has failed.

I understand that stalling shouldn't be an issue, though the risk of amplifying underlying unknown issues - ISV, vacuum, still worry me a bit.

I used to own an s2000 and that had a stock 13 pound flywheel with a very responsive engine. I noticed sometimes that I'd actually have to throttle blip on the upshift to keep the shifting smooth.

Does the LWF act this way in our cars? I have zero access to an LWF to test out, so that's not an option. Anyone with a post '95 regret the move?

pp000830

If your engine runs smoothly don't go looking for love, you will find her and she will be an expensive date.

Dual Mass Flywheel Failure- This is a very uncommon issue for street driven cars. - IF your car seems to idle a bit too rough and you have been experiencing:
 The check engine light and;
 A reoccurring non-cylinder or;
 Multiple named cylinder “emission relevant misfire OBDC code.
AND you have addressed the other less invasive sources of this such as:
 Run the quick, unplug-the-primary-distributor, belt test,
 Verifying there is not a vacuum leak on the engine,
 Cleaning the idle valve,
 Replacing the distributor caps and rotors and,
 Addressed any cylinder specific reoccurring misfire codes, wires, plugs, and injector (done after the items above and a clearing of the codes with the misfire code still returning).
You may have a problem with the dual mass flywheel (DMF).
The reason for the DMF in the 993 is to address the engine‘s ignition-induced rotational speed irregularity cause of vibration in the driveline. At certain speeds ignition timing matches the natural vibrations of the driveline amplifying the vibration causing transmission rattle and body boom.
I am told the litmus test for a failing DMF is to use the PSTII (Porsche tool), put the car in the air and with the car in gear, read the speed sensor directly. I'm told that it will rapidly slow and speed up out of sync with the engine RPM. Also, LuK offers a DMF testing tool that physically tests the flywheel once the transmission is removed. If the flywheel needs to be replaced light weight non-dual mass flywheels are widely discussed on this board as a replacement option.
I researched the non-dual mass light weight flywheel option and found that if you replace the flywheel with a light weigh single mass flywheel be aware that you should expect a good bit of additional noise, per Luk testing data and Rennlist postings. Some who have done this like the concept and throttle feel of the simpler flywheel and feel it is a good tradeoff for a perception of improved performance. Others have found the noise bothersome. Luk testing has shown installing a single mass flywheel can accelerate wear on engine/drive line components due to increased torsional impact loads to the engine and transmission. Some have experienced idle problems with the light weight flywheel requiring DME software changes to fully address.
My gut tells me that if your car is tracked regularly a single mass flywheel or refreshing the DMF flywheel during a clutch replacement may be worth considering. However, for street driven cars that run well but seem to throw a lot of random misfire codes, are not exhibiting a rattling sound when the ignition is switched off and have passed the definitive test above, I feel, should retain your existing installed OEM DMF at clutch servicing and look for other causes of the misfire related engine light.
Andy

Tlaloc75

I can speak from experience, because I recently did this (last year). I also had a sneaking suspicion that my DMF was failing. I would hear a rattle at shutdown, but pressing in the clutch would make that noise go away. I also would occasionally hear a clunk when accelerating in first. I bit the bullet, pulled the clutch and flywheel and lo and behold - the DMF was indeed failing. It wasn’t my imagination. I installed a LWFW and GT3 pressure plate and love it! The engine is eager to rev and just that much more willing, especially in lower gears. Downshifting is a real pleasure, as the engine revs up so quickly when needed. I don’t need to rev-match on the upshift, shifting through the gears is natural and smooth. There is slightly more noise when below 2k RPM in first and second. I hardly notice it because I spend so little time below 2k and the noise is not intrusive at all. Besides that, there is no additional noise that I have noticed.

In a 98, you’ll have no trouble with idle. Let the car idle for 10 minutes after the work is done, the DME will learn the new setup, and you won’t have any issues with it whatsoever. I think on the early cars (95) there can be idle problems, but the later DME programming does away with that.

Good luck!

mhm993

I have that setup on the track car. Love it on the track car but wouldn't put it on a street car. Its noisy rowing up through the gears and it sometimes does just a little searching at idle. My two cents.
If I recall, Steve W in Oregon sells a mid weight flywheel.

Tlaloc75

I wonder if there is a difference in noise levels from car to car, or perhaps just different levels of tolerance... because I hardly notice it at all.

95 C4 993

While I enjoyed the feel and performance of the LWF, it was my biggest 10 year love/hate putting it in my 95 993. Multiple chips, ISV cleans, tuning, modified driving behavior, my mechanic engaging with Steve W, and his contacts (my wrench) in Germany, and multiple trips to the shop. Nothing like dropping 10k over a few years (mods/60k tune/cleaning/chips, ect) only to have it still stall. The 2x I dropped the most $$ on it, it stalled less than 2 blocks from the shop each time. For each their own but I wouldn't touch a LWF or MWF on a 95 if I could turn back time.

rk-d

Thanks for that. Car runs well and no codes or CEL. Just a little rumble when I shut her down. It's not a big deal and I'm not too worried about it since it otherwise seems solid. Clutch has 44k miles and feels fine, though it is squeaking despite changing the slave. Maybe fork bearings or throw-out or pilot tube or pressure plate. So I'm planning ahead on this one. I was going to do an ISV clean or replace and refresh the distributor caps/rotors as well as some regular "while you're in there" stuff. Being a C4S, I'm pretty sure it's engine out.

Great to hear!
MWF not available when I asked.

Definitely would avoid if I had a 95. I've not seen a lot of complaints on post 95s. I'm willing to sacrifice a little refinement for responsiveness, but I don't want a headache.

WRXdriver

I realize a 1995 data point not helpful here, but maybe for future Search Function user.

I have LWF and RS clutch on my 95 and love it. The only noise I’m aware of is a mild, Ducati-like rattle at idle with clutch released in neutral. I like the sound, and definitely not intrusive. It does annoy me upon cold start when outside temp is below about 40* F. In that case the RPM will usually rev and fall off in a cyclical manner, but it obviously stops as soon as clutch is engaged and generally doesn’t reappear in neutral at idle after just a minute or two of driving. I have a chip, but when I first bought the car it would stall frequently when stopping, especially if engine RPM was reasonably high and load suddenly erased, such as coasting up an exit ramp off a highway. I quickly developed a habit of blipping the throttle as RPM falls and don’t even think about it anymore. The car wasn’t used much when I bought it, but now I drive it a lot and have noticed when friends operate it more conservatively without blipping throttle it does not die. Maybe stalling issue more attributable to previous low usage than LWF.

Generally speaking the slightly more aggressive LWF/RS clutch are well suited to a modded car (short shift/goldenrod mod, lowered suspension, exhaust etc). I’d do it again if clutch replacement was required, but not sure I’d feel the same if my car was close to stock. Bottom line isLWF unlikely to make or break your 993 driving experience.

ed devinney

I've had a LWF in my 96 (street car) for about 50k miles. I generally agree with WRXdriver - it can be fun part of a modded car, but may not fit what you want the car to be. My car is modded but is a daily driver, and I find the gearbox noise to be a little out of character with the kind of GT car that the 993 really is.

That said, when I recently had the motor out and trans rebuilt, I found the flywheel and pressure plate to be in excellent shape, so I scuffed them up and popped a new GT3 disk in between - the noise might be annoying sometimes, but it wasn't worth the $ to go back to DMF.

Tlaloc75

These are good points. I have lots of RS parts on my car, including motor mounts, bushings, and sways so I’m going for a rawer more precise driving experience. The LWF adds to that and enhances my enjoyment for canyon carving style drives. If you were going for a more cushioned GT experience, the LWF makes less sense.

rk-d

Interesting thoughts. Funny hearing the 993 called a GT car. Even in '98, I'd have considered it relatively raw. But I suppose it's more GT than the cars that came before it.

I have been slowly modding this thing up. Had it lowered with m030 springs and new shocks and have a Fister Stage III on it's way. So it won't be a quiet GT cruiser. I've considered the goldenrod, but will pass on short shifter, I think.

I only drive on the weekends, and tend to drive it somewhat aggressively. I've been having fun practicing my heel/toe with it, which is what started me thinking about an LWF. No stop and go, no daily driving or errands. I'm really interested in maxing out the fun component, so a little noise and little roughness is ok.

shiraz

Mine is a '95 RoW car, M150 ( dirty fuel option - no/ hollow cats) a previous owner installed single mass flywheel with Steve Wong chip, HDs & H&R springs - it's low. I've never experienced any stalling issues. I've installed the semi-solid engine mounts from Rennline. It baffles me that some people have issues with NVH, if I wanted an S-class/ Lexus, I'd have bought one.

Double de-clutch your downshifts - the car will thank you.

Endoman

My '94 had LWF fitted several years ago. It stalled occasionally and had the usual gearbox chatter probably more intrusive due to RS gearbox and engine mounts and removal of sound deadening. Didn't bother me as the improved acceleration in lower gears more than compensated.
Last winter I converted the car to Vram manifold with RoW '96 ecu and standard chip. No more stalling. The gearbox oil was changed from Mobil SHC 75/90 to Porsche (Shell I believe) ,the gearbox noise is louder and happens earlier as the oil warms up. The gearchange is not as slick, so I'll be going back to Mobil

Harold

Ditto this. I have a pre 95 and it stalls whenever it wants. I will go back to original sooner or later....

Coleman

On my 95, I put the LWF in~ 1year after initial purchase, (+Steve Wong chip) and that was about 14 years ago... Overall, I found it so much easier to drive, when I drive friend's 993's /996's that still has the DMF, I find it really difficult to match revs, to blip and to get the engine RPM's generally in sync with various gears.. The sluggishness of having the tach fall from 4K to idle with the DMF makes cars seem unresponsive and heavy? but then again I've been using the LWF so long that but just seems natural.. @WRXdriver I do have all the same downsides of it the LWF as you- , I have a hunt at idle at initial start up's under 40°, until maybe the enrichment cycle finishes? Usually about one minute. It also used to stall when coming off of heavy use on to an exit ramp or something, but now I've developed the habit of blipping the throttle when I'm coming off throttle to a stop, and it never seems to stall.. There's definitely a bit of increased noise.. When Hegesheimer Porsche did the work on the car which included top end, RS cam's, and a full tranny rebuild./regear/LSD in addition to LWF, I think they took out some extra tranny bushings or something(?) Replaced some softer mounts with solid ones, and when it's warm, and idling, it's definitely got a bid of "Coffee can of bolts" sound... I don't hear any of it while driving, except maybe a bit more gear mesh.. No way I would ever go back, and this is my daily driver...