andrew2008

I don't think torsional engine vibrations can be fixed by balancing
the engine. Since torsional vibrations are rotational, even if the
engine is balance perfectly, there will still be torsional
vibrations.

Ur20v

^^^ Agreed. You need perfect dynamic balance and damping. Note James' comments that the destructive forces are in the lower rpm ranges where they get multiplied and applied when the hit certain harmonic frequencies that can be destructive (seen the film clip of suspension bridge rip it self apart when isolations reached a certain level?), you can spot this as you drive around- notice vibrations and rattles are worse at certain speeds/revs or the drone from the exhaust at certain speeds in certain gears

The DMFM was designed to increase gearbox life by protecting syncro's in the gear box from wearing out

Rob996

This is certainly alarming news.. Or is it..

My 2010 GT3 was suffering from a bad shudder when In reverse and starting off in first gear.. The problem was related to either the clutch or the flywheel as diagnosed by my mechanic. Now the dilemma, do I replace the defective part with original equipment or do I upgrade to the 4.0 kits which includes the lightweight flywheel clutch, bolts etc.. You know guys know the kit I'm talking about suncoast.. My car has full Porsche warranty but as we all know that wear parts like clutches and flywheels are not covered therefore this expense is all mine.. A big part of the investment is labor when dropping the engine and removing the clutch or flywheel.. I decided from a preventive maintenance approach that when the engine was dropped I would replace both flywheel and clutch with the 4.0 upgraded option.. Which BTW lots of you guy on RL were doing and recommended.

Fast forward. I had this work done last winter and I couldn't be happier with the results.. The engine feels more responsive .. As the it feels like it revs freer.. The shifting is smooth and the shudder is entirely gone.. This car is used 60% on the track and the additional engine clatter from the LWFW makes me smile.. Although probably not recommended for the folks who street only..
I understand why porsche uses the heavier flywheel, as it quieter and smoother and probably enables the transmission to last longer..

Lets not jump to conclusions without all the facts and information on what happened to this guys engine?. does it make sense a porsche LWFW works on the rs but not the non-rs..

This sounds like a rare isolated incident, which requires more data..

Thanks

ranger22

Huh? Drop the engine?

mdrums

What is different internally between a 2010-11 GT3 and GT3RS 3.8 engine to make it ok for the RS to come with a LWFW

andrew2008

With the development work being done on a new damper, it would
be very useful to be able to measure and quantify torsional vibrations
with the DMFW vs LWFW vs LWFW + damper. I don't know if this has been
done, since this would need to measure the twisting of the crankshaft
and probably isn't easy to do with the engine in the car, but it would
provide definitive data as to the effects of the various flywheels and
dampers.

RedRSA

Short answer from all I can find: nothing. Nothing in terms of parts, and definitely nothing in terms of combustion-induced harmonics (i.e., same flat six design with same displacement, bore and stroke). Nothing to explain why Porsche states that the GT3 wasn't designed for it, thereby implying that the RS was designed for it. Perhaps finer precision in balancing the rotating mass, but nothing definitive to confirm that this is true; and even if it were, while inherently beneficial to be precision balanced, rotational balance is a totally separate issue from the combustion harmonics.

As far as "ok for the RS to come with...", even though Porsche designed and sold it, maybe it isn't? I don't think anyone would argue that the RS has experienced more failures than the GT3. No one can argue that the single biggest difference between the RS and the GT3 isn't the Single Mass flywheel (being lighter weight gets most of the attention, but being single mass is the significant characteristic related to vibration). The pressure plate was a weak point, but I doubt the additional 15hp was what exposed it; more likely extra vibration, combustion harmonics or otherwise.

GT3 Cups have successfully used the SM/LWFW for more than a decade. However, they don't have emission controls such as the vario-cam whose actuator bolts can be shaken loose, they typically live above 5k RPM which reduces their exposure to destructive harmonics, and they have quite aggressive refresh schedules.

Is it safe to swap? I don't know. There are some intrinsic benefits associated with reducing the rotating mass and eliminating the dual mass unit that has itself been prone to failure on the track, but there is no reason to assume that some of the reliability issues wouldn't also be inherited. Mine is a track car, so the RPM range would help keep me above the most critical harmonic ranges, but I don't like the idea of introducing new reliability concerns. I will need to decide in the next couple of days so parts can be ordered.

audipwr1

Lots of added risk for more car rattles

I'll keep my dual mass

Tacet-Conundrum

The point is they aren't standing behind their own product, it's not like it's a a V-double..... Wait a second it makes sense all of a sudden.

Back in the early 90s when the fast and furious crowd was barely starting up if you modified something on your VW and something else totally unrelated to the modification, say lowering the car and the radio stops working four months later VW would not cover it because the car had been modified and how can you tell if the lowering of the car caused the radio to stop working? It's because of **** like this that some warranty laws were changed in favor of the people who bought the car. It was very obvious that the OEM Manufacturer would not pay for warranty work on a system on the car that was totally unrelated on the car that needed work or had failed!

This all makes sense to me now since VW owns Porsche now it's obvious that many things haven't changed and it's just Chicken-**** that Porsche won't spend the money to fix it. Beyond labor which is charged out as a Percentage to Porsche from a dealership; like health insurance and medicines, the cost of the replacement part only Porsche knows. Which is probably on Orders of magnitude cheaper than the MSRP OEM List price. But then again they would only be able to replace all the broken bits with original parts that came with the car off the lot. I.E. even if Porsche did cover it the car's replacement would not be the Fly Wheel from the RS.

Don't think of it as Porsche making the call, think of it as VW. Maybe I'm being too critical of VW owning Porsche when we all know it should be the other way around. But there's nothing we can do about that fiasco - I wonder if the two families send each other Christmas Cards. Sorry about going off topic at the end here.

I'm just grateful that Porsche remains the top developer of high performance technology. Not Audi or the Lamborghini... I just wonder how they let Audi and Porsche develop separate technologies for racing?

/end babble

JasonAndreas

The only difference between an M97.77 with and without I004 are the cylinder heads.

Fisher

Mr. Technical Guru, please enlighten me about how your statement relates to a Mezger engine in a 997 GT3/RS.

JasonAndreas

I'm not sure I follow you? The 997GT3.2 engine is a type M97.77. Any changes for the RS will be listed in the parts catalog with option type I004. Unless I am reading the catalog incorrectly (which is certainly possible), the GT3RS used the cylinder head with part #997.104.001.85 while the regular GT3 came with 997.104.001.96. That is the difference between the engines?

The last time Porsche admitted to having a problem with unwanted resonant frequencies they had to reduce the thickness of the PORSCHE logo on an intake manifold... And the last time they admitted to 4th order harmonics destroying an engine that didn't have a torsional vibration damper, they ended up stiffening the crankshaft and lightening parts of it. Do we know anything about the engines that failed other than "they failed"?

Yoops Racing

Interesting porsche cpo'd my gt3 with a rs lwfw, rs pulley and new bolts. I verified this on 2 separate times 2 separate dealers.

RedRSA

All of this is correct. No idea what is different on the heads, but suspect it had to do with matching up to the different intake and wager it had little/no effect on harmonics.

This is indeed very interesting. I have not read a CPO contract, though I understand that they are very thorough; were there any "exclusion" clauses where those parts would be excluded from coverage, either explicitly or implicitly through verbiage such as installation of "non-stock parts", etc.?

Yoops Racing

Keep in mind. My swap was done with OEM Porsche parts. This is why the CPO covered it. What I found out from Alex at Sharkwerks at the time of purchase, is that a lot of folks will do the LWFW but neglect to also do the RS pulley in conjunction. Maybe this is where the problem started for the original thread owner All I know is that Both Bramen Miami, (where I purchased)and Hennessey Atl verified the CPO. I have had the car for 4/5 years and never had the first issue. I would lay blame for the engine problem either from the installation itself or possibly using the stock pulley instead of the RS pulley/bolt kit.