Jim_me

I have a 96 C4S. A friend of mine told me about installing a lightweight flywheel for added performance. I imagine it might help some in the form of acceleration but how much ? since its pretty expensive. Also, are there any issues with this ..?

Martin S.

The first issue that come to mind is stalling at the intersection. I have friends with the lightwiight wheels and they have told of this problem. I am certain you will get more technical responses...this seems to be the main drawback.

There are various iterations of lightened flywheels. If you go super light, this is where you'll probably experience the stalling problem, or so I have been told.

Viken

Martin,

DJ has an RS lightweight flywheel in his C4S and he never stalls it. In fact, I drove his car and didn't see how anyone would stall it.

Steve Weiner-Rennsport Systems

Hi Jim:

Up until now, this has been a real problem to deal with and the various solutions have somewhat ameliorated the benefits of the lighter flywheel.

Ther are 2 lightweight flywheel setups: one is the Euro Carrera 3.8 RS one and the other is the 3.8 RSR race setup. This latter one is not recommended for street use although its the "cat's meow" for race cars not wishing to use the 3-plate Tilton setup with aluminum flywheel that Aase Racing offers.

The Erup Carrera RS one is a single-mass flywheel that is almost half the weight of the OEM dual-mass flywheel. This is much more durable and reliable part than the stock component and its really worth doing, IMHO. The difference in engine response and shifting is really neat.

There are 2 solutions to fixing the stalling problem. One is a software fix that is done when the car is chipped. The other is an RS flywheel that has some additional weight added back into it to relieve the potential for stalling.

Since we have helped develop the software fix, I'm somewhat partial to using this rather than the "band-aid" solution by adding weight back into the lightweight part.

The '96-on OBDII cars handle the RS flywheel conversion much better than their predecessors. In any case, I would recommend a thorough cleanout of the idle stabiliser valve if some stalling is experienced.

Hope this helps,.....

[ 06-19-2001: Message edited by: Steve Weiner-Rennsport Systems ]

Rick in Portland

Andial sells a light flywheel, but adds some weight to it so the engine won't stall. If the flywheel is too light, the engine won't recover from the RPM dropping too quickly unless the ECU has been reprogrammed.

Rick

Randall G.

I had the RS LWF installed in my 964 at 34k miles, after the original DMF went out. Loved the way it revved, but hated everything else about it. Stalling while pulling into the driveway of the local Italian restaurant, embarrassingly erratic idle when running the AC.

At 50k miles, I convinced Porsche to install a LUK flywheel in my car, provided I paid for the labor and had a major service performed at the dealer. I was quite happy to go back to the LUK DMF. I'm not alone here--many 964 owners have converted back to the LUK DMF after replacing their original flywheel with a LWF.

All that said, what Steve W. writes sounds reasonable ... that the stalling problem can now be addressed. Personally--after my experience--it's going to take a lot to convince me that LWF's are practical for street use. Maybe someday I'll drive another car similar to mine with a LWF that works under all circumstances?

Pete911air

We installed over 200 light flywheels into 964, 993 and 993tt. No problem with stalling, surging at Idle and great driveability. Am I correct Steve Weiner ?
I gues experiance does not couny for much.

Randall G.

Yes, DJ told me that his LWF w/Porsche Motorsport clutch works wonderful (DJ, are you out there?) He also told me that he has a friend with a '95 993 that put the same clutch and flywheel in his non-vario-ram '95 993: "the car ran horrible and stalled all the time, perhaps due to an aftermarket chip with 'funky' programming." This person wound up replacing his LWF with an Andial "semi" LWF.

The '95 not working well with the LWF is consistent with Steve writing "'96-on OBDII cars handle the RS flywheel conversion much better than their predecessors."

Steve in SLO

What about the noise from the drivetrain with the RS FW? I was told this is another potential irritation with the conversion. I would love to have the revving freed up, but would hate to have intrusive gear noise as a result. TIA,

DJ

Hey Y'all,

Steve and Pete obviously know way more about this than I do, but I've had this clutch/flywheel combo in my car for about 10,000 miles. From Steve's description, I'm not sure which one I have... I would have thought that I have Euro Carrera 3.8 RS except that Steve mentioned that it's almost half the weight of the stock flywheel, and I think mine's lighter than that. I didn't weigh it, but it felt more like 1/3 the weight.

I'll also agree with Viken, that the stalling is not a problem. I've only stalled it once, and that was when I was reversing up hill at idle while talking to someone (probably just not paying attention, but still embarassing).

I'll disagree with Rick, at least in regard to post-'95 cars, I don't think that the software fix is necessary.

With the stock clutch, one hard launch would have my clutch slipping, but this new one really bites. It takes a little finer touch to drive it really smoothly, but it's not really a big deal, although it does seem to have a somewhat narrower range of engagement. The lighter flywheel makes a difference that you can feel--a little quicker revving--especially in first and second gear. The car definitely shifts better, up- and down-shifts, because of the quicker revving.

There is a new sound (noise?) associated with this setup, but with the stock interior and the windows rolled up, I almost couldn't hear it. With the windows down, and heavy throttle there's a rattley-sheetmetal sort of sound under 2,500 rpms... but you've got to be listening for it. For a while I thought it was just my imagination. Now I've got the rear seats and all the sound insulation removed (had to make room for the roll-bar, and lose a little weight), and I can hear the rattle pretty clearly at wide throttle openings under ~3000 rpms. It's not bad though.

If I didn't already have it, I'd get it.

[ 06-20-2001: Message edited by: DJ ]

Steve Weiner-Rennsport Systems

Hi Gents:

Like many things in the world of Porsche, this might not be for everyone but its definitely a performance enhancement with few operational drawbacks and does improve durability. Up to now, the stalling issues with the unweighted ones, made this something to think about for street use. This has now changed.

A few points here:

1) The worst offenders for stalling problems were the 964 series and the '95 OBDI 993.

2) The '96 and later 993's are OBDII and these cars seemed to handle the RS light flywheel setup without much trouble unless there was something else wrong. Carboned up throttle bodies and idle stabilizer valves come to mind. This software modification is not needed on the OBDII cars.

3) We originally fixed the 964 stalling issues with a modified idle stabilizer that did the trick. This also worked with the '95 993 cars.

Now, we do the same thing in software and this is usually done when the DME is reprogrammed for more performance. No more stalling troubles!

Andial's RS flywheels with the additional weight added also took care of this problem. We simply wanted to preserve the lighter weight aspect and retain all the benefits and therefore required a software fix.

There is no question that the lack of flywheel mass and damping makes the typical G-50 low speed gear rattle more audible and for some people this is not acceptable.
This IS a performance upgrade and this is the only real compromise that I can think of.

Personally, I love it and when combined with a good set of close-ratio gears, this REALLY makes these cars perform without affecting emissions compliance or causing check engine lights,....

Randall G.

I don't remember being irritated by excessive drivetrain noise when I had my LWF, so I imagine it couldn't have been toooo bad. Perhaps I was so annoyed by the stalling and erratic idle that I didn't notice ?

Robb M.

Before I put the TT motor in my C4S I had the clutch and flywheel changed.

I had the really light flywheel put in as well as a much more aggressive clutch.
I did have some stalling problems in the beginning but as soon as I took off the idle stabilzer vavle for a cleaning that problem quickly went away.

I too notice this sound and my mechanic has explained it to me as this. The original porsche clutch uses a rubber band that is stuck in the middle of the flywheel to make it easier to engage and dis-engage the clutch, the racing clutch I now have does not have any kind of system like this..it has 3 blades all with 3 springs each on them. The noise you are hearing DJ is the springs rattling on the clutch plate...I have it too, with the C4S motor and still now with the TT motor as I'm using the same clutch and flywheel setup...
it only is noticable at low RPMs or when lugging the car slightly...not that annoying IMHO...

tom_993

I have one of these. It's a long story. First of all, I have a '95 non-varioram, OBD1, C2 coupe (and Robin thinks he has a DX model!). I needed a clutch, so I asked around about LWF's. About half the responses were positive and half negative. I spoke with my mechanic. He said that the clutch job with or without the LWF would be about the same cost. He also promised to put the stock unit back in at no cost to me if I was not happy. Since I had nothing to lose, I went for it.

When I got the car back, it stalled at every signal or stop sign I came to. Just push in the clutch, and the engine would stall. This was unacceptable. I had to heel/toe when I came to a stop to prevent stalling. I also had significant surging. My mechanic "modified" (whatever that means) the idle stabalizer and modified some of the funky programming in the chip that DJ refers to. This helped, but I still stalled all the time and still had surging. The idle stabalizer is clean, as is the throttle body.

The next step my mechanic did was to remove this flywheel (yes the engine came out again, making good on his promise) and send it to Andial for their modification. This is the Andial version with some weight added back on. The stalling problem has been fixed, but the idle does drop to about 600 or so everytime I come up to a signal (the headlights dim at night). This doesn't hurt anything, but somehow it doesn't feel "right" for a Porsche. The surging problem is better, but still there.

As for pros and cons, the best pro is the increased torque at low RPM's. When I come around a corner too slow for second, but to fast to downshift to first, there seems to be a lot less lugging when I step on it. The biggest con is the surging, which I'll describe shortly. Like DJ says, it takes a "finer touch" to drive smoothly. I have to concentrate on shifting more (no autopilot any more), and quite regularly shifts aren't real smooth. It requires a little more slipping off the line (due to less inertia). It probably helps my 5-60 times (on the order of .1 or .2 seconds), but hurts my 0-60 times. There is some increased noise, a rattle at idle and a growl when I step on it at low RPM's. Neither noise is objectionable.

As for the surging, I understand this is caused by the ECU cutting fuel and adding it back in. What happens is that the ECU cuts fuel anytime the throttle is closed above about 1500-1800 RPM. This is for both mileage and emissions. When this happens, you get compression braking from the engine and you lurch forward. Anything that causes the fuel to come back on (touch the throttle or rev's drop below the limit), will cause strong acceleration and you lurch backwards. Sometimes you get in this on-off-on cycle and the only way to break it is to push the clutch in. This does not happen when you accellerate smoothly, through first and into second. It only happens when you need to modulate the throttle in a parking lot or traffic. I got stuck in traffic a while ago that was moving right at the critical surging speed, and it was miserable. What I do is lug it in second or alternatly give it some gas and coast, as first is basically unusable except in cases where I can smoothly accelerate and shift to second. I would be very grateful for solutions to this problem (Steve W?). I had this surging before the LWF, but much less. It's worse now without the heavy flywheel's inertia. It's so bad now that I debate putting the stock flywheel back in, but that would be at my cost since I've already used up my mechanics promise. It's also worse when the engine is cold (it even happens in second). I suppose this is because the ECU is using a different map. With the lightest flywheel (before Andials version), I could feel the fuel cutting in and out even in high gears, but the car had so much momentum that you weren't lurched around in you seat.

Steve Weiner-Rennsport Systems

Hi Tom:

The detailed account of your experiences with the lightweight RS setup is quite well appreciated and very familiar to me.

I am not sure whether you have a stock chip in your car or not and if not, I don't know exactly what corrections were made to help the engine management system deal with the lighter flywheel. This is not easy to do!

IMHO, a reality check is in order.

One must not overlook 2 things:

These RS flywheels were intended for the Euro OBD Motronic system, not OBDI or OBDII. The operating environment and thus the programming in those ECU's are very different from what the EPA mandates here in the USA and they do affect low-speed engine response differently than the stock dual-mass package and Motronic programming. In other words, these are near-racing parts and will make the car slightly jerky at certain points in the RPM range and at small throttle openings. They were not intended for stop-and-go city driving.

There is no question that installing any racing or high-performance part represents a compromise of varying degrees. Some are inconsequential and some are readily apparent. Each person must determine for him/herself whther the tradeoffs, large or small, is worth the gains in performance. This really depends upon application and how you use the car.

Porsche's engineering is first-rate and they have produced and sold the very best compromise available. Don't forget what they must accommodate when selling cars here in the USA; emissions, drivability, all around-daily driver usage, inconsistent fuel quality. When we modify a car for quicker acceleration, top speed, crisper and more neutral handling, we invariably sacrifice something, to enhance something else. Its no different with any car.

Installing cams, high-compression pistons, close-ratio gears, LSD's, firmer suspension packages, all require a compromise to be made. Even the very best of engine performance chips require finding and using the highest grade gasoline that you have for best performance. Nothing is free.

Same for light flywheels,.....my own car has a 6 lb Tilton flywheel that makes daily use of the car rather tricky and sometimes tedious. Overall though, its very well worth it to me for what it does. Some people find it too difficult to live with and thats no indictment of them, just a fact.

I would recommend anyone contemplating ANY kind of modification to their car to really do their homework and get a ride, or drive somebody's car who has done what is under consideration before any money is spent. Putting forth some effort in this regard will pay big dividends in getting the most value out of your performance investments.