Michael Petersen

Thanks for the clarification Silver TT... I appreciate it. To be clear, Im not a snowflake, Im far far from it. I just like to see these blogs about cars (which we all share a love for) to be a step above the the average junk I find on mainstream social media. Let's debate the problem, but not attack a persons IQ.

I love the technical discussions, but I don't approached the immature criticisms, especially coming from a moderator. "Holding a horse under water, and waiting for the bubbles to stop"? Are you guys teenagers? This thread is starting to sound like a twitter rant. Lets keep automotive forums about our common passions and leave the criticism for other social media accounts. I also think you may find some of your members know more about cars than you give them credit for. But, your counter your specific technical points: 1. No one said they were, but many are not balanced out of the box, which is an issue. And some machine shops simply don't want to add the cost of developing processes and tooling to specifically deal with low volume alloy flywheels they see infrequently. --> I'm installing an AASCO aluminum flywheel. They are a good brand and I have seen no data that their balance is better or worse than factory porsche flywheels. It would technically be easier to balance a single mass flywheel than a dual mass, as there are tolerance build ups in the rotating mechanism of the dual mass that may make it actually harder to balance. Again, I have no data to know which flywheel is better balanced. 2. Regardless of what you may think, the dual mass flywheel absorbs torsional harmonics from the crankshaft, which in most Porsche engines is cast, not forged, and the rotating assembly is not very closely internally balanced from the factory. Hence the need for a torsional harmonic absorption device like the DMF or suffer cracking issues. -->. Here is a very good article on the physics of the dual clutch, it was writing by LUK during the development of the dual clutch design many years ago, See pages 69-93. https://www.schaeffler.com/remotemedien/media/_shared_media/08_media_library/01_publications/schaeffler_2/symposia_1/downloads_11/luK_kolloquium_en.pdf. It is true the dual mass flywheel reduced the vibrational forces on both the engine and the transmission, but we are effectively replacing the dual mass flywheel with a friction plate that has incorporate springs that gives the torsional decoupling of the engine from the transmission. Under load, the dual mass function moves from the flywheel to the friction plate. The rotation of the engine has no idea where the reduction of the true torsional peaks comes from, it just knows the peaks are lower. It is for this specific reason that it is recommended not to use a rigid friction plate with a single mass flywheel. 3. The GT 3 RS engines come with a forged crank, unlike most Porsche engines, and the rotating assembly is internally balanced to a much higher standard than the regular production engines, which are two of many reasons why when new short blocks were still available, the production versions sold for less than $20K, while the GT car short block was well north of $50K. --> I think we strongly agree that better balanced engines are always better in high-performance applications. I also think it's a good point the GT3 RS uses a forged crank versus a cast crank of other variants. 4. Short answer: both, so while the sprung disk may make the car more drivable, it didn't prevent crank cracking. --> You may be correct, but I would like to see some data (any data) that backs this up. There are tens of thousands (maybe hundreds of thousands) of aftermarket lightweight single mass flywheels in the market today, and we do not see widespread complaints of crank failures. I see a lot of opinions, just not many actual proof points. In the beginning of this thread someone mentioned Jake Raby thought an engine failed do to a single mass flywheel. Instead, maybe the crank had a large grain boundary diffusion when it was manufactured and it was destined to fail, and it just happened to fail with a customer with single mass flywheel. We will never know. But we should be able to look at the quantity of field failures and make an education assessment. Im installing a single mass flywheel with a spring friction plate from Sachs; it will have hundreds of track hours per year and I PROMISE to report back here if I have an issue so other can benefit from my learnings (or mistake!)

I don't understand all this negativity on lightweight flywheels, only because one person thinks it may have been the cause of an engine failure. I'm with @Maytag on this... 1) lightweight flywheels are not any harder to balance than heavy flywheels. 2) The dual mass is designed to reduce the pulsing forces into the transmission and reduce gear noise, while it also smooths out the pulsing torque forces into the engine that is only a secondary benefit and the highest forces in the engine at the cranks are due to the piston. The dual mass flywheel would have virtually no impact on these crank forces. 3) The lightweight single mass flywheels were/are used on GT3 RS cars for years. 4) If you install a lightweight single mass flywheel you should also install a spring friction place to take the place of dual mass flywheel. For the few failures that have been documented, what type of clutch plate did they install (springer or original)? Net net, until I see some data backing up the failures, I'll take my chances and go for the increased performance.