Improving the M96 during a rebuild

I am intrigued by the possibility of addressing two of the 24+ "Modes of Failure" of the M96. 1. The narrow rear main bearing with the heavy, cantilevered DMF contributed to my engine failure(I speculate). Once the DMF has excessive freeplay(mine was 15mm total!) ,it does more harm than good ? The narrow rear main bearing gets 'hammered' by the worn DMF .Fortunately it did not crack the crankshaft !The rear main bearing debris feeds directly to #6 big end bearing which is then starved of oil ,it fails and starves #5 big end bearing. Is there a solution that gives the necessary harmonic balancing ?A LWFW is rejected by some experts because of the lack of alternative crankshaft damping. I have had the new LUK DMF+pressure plate balanced but wondered if lightening the DMF around the periphery would significantly reduce the cantilever forces that overload the oil film for the rear main bearing? The thickness of the DMF has already been drilled on one location to achieve perfect balance. I was thinking of drilling more lightening holes around the entire circumference and then re-balancing. Schaffler/Luk claim to have a new ,lighter DMF but I can't find info on a retrofit lw-DMF for the M96. Anyone have any info on this? 2. Excessive heat/poor cooling/oil-film breakdown on bank 2 (4-5-6). Bank 2 is where the problems seem to start based on hours of combing through posts here.The trust face of 4-5-6 runs hotter than 1-2-3. So what can be done to address this ? I have 3 clean radiators, the low temp thermostat, new water pump, Joe Gibbs oil.What else? I would like to replace the oil-heat exchanger with a real oil cooler but there is no suitable space in decent air flow(??). Are there any proven mods. to the cooling system that would give a balanced flow to both banks instead of favoring 123 ? I can not find any. On other engines I have worked on that had similar problems we used a Davies Craig supplementary electric coolant pump.It worked very well. If anyone can point me in the direction of any proven solutions to these two issues ,I would be grateful.And it would help many others who do M96 rebuilds in years to come.

Jake Raby of http://flat6innovations.com/

and Hartech and Autofarm and Rennsport I read all their generous and some times cryptic offerings conscientiously but have not found the answers to the two issues raised above - have you?

Jake will only give you the "correct" answers in his book or in an engine he builds for you. The JG oil is a step in the right direction.

Here is an idea -why not ask LUK ? I believe that I read you were in the engine development business -surely there must be a way to get to their engineers ? Your hypothesis is that the DMF caused the failure .If I read Jakes posts correctly he did not concur .In fact I think he said he has seen the same failure with a lightweight flywheel . Heat and oil pressure could be a bigger culprit depending on how the car was used .If it's a lot of stop and go with protracted idling that could be a factor . Another point Macster has north of 250,000 miles on his flywheel so they may not be that fragile . Just food for thought..............

Ceramic coated exhaust headers &/or rerouted pipes further away from the engine like 987's. As for reducing load on the rear of the crank, aluminum pressure plate.

Keith, I have noticed you often make helpful suggestions for Forum members. Thank you! The ceramic coated headers are an interesting and practical suggestion.I'll try Embee as you kindly suggested previously. I suppose that deleting the pre-cats(NOT the main cats) would also help if it could be done without triggering a CEL ?A pair of s/s headers +ceramic coating may work well? Dcd, Agreed the LWFW is not recommended.What I proposed was a LW -DMF.The problem with LWFW is not that they break. They crack crankshafts -no harmonic balancer. Byprodriver has an interesting alternative- a LW-pressure plate.That is clever because it is even further away from the rear main bearing and therefore is a bigger problem(cantilever).My stock PP was balanced as a unit with the new DMF but if I can find an aluminum one at a reasonable price,I'll try it. This was a common mod on the old air-cooled P-cars. Thank you both for your contributions.

Until Jake releases all of his research, most of us are just guessing. I would think that when he completes his studies and publishes same, we may all be amazed at how the M96 engine survives the occasional drive much less being DD. I hope I am wrong but from JR's pre-release of bits and pieces (no pun intended), it seems like there is much bad news to come. The only "real" solution would be a NHTSA mandate requiring all affected Porsche's be immediately flat-bedded to JR's facility for the "cure".

Agreed Krazy. But I have abandoned all hope that Jake's book will be in my Christmas stocking. I have dragged out my rebuild with distractions like gearbox rebuilding in the hope that a publication date would be announced. He has been writing the book for 5 years and has had many distractions I am sure ! I am not complaining -if he had stayed off the Forum and concentrated on his book ,it would have been published years ago ! Instead he often pops up to help(or tease) us.

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I should have mentioned that, to the best of my knowledge, no aluminum pressure plate exists for a M96/97 engine. I looked into this in 2010 while I was rebuilding my engine, with the intent to develop one if none was available. I saw that a Centerforce clutch for a similar application sold for about $1,500 & decieded against pursuing it further.

My knowledge of aluminum pressure plates is worse than yours Keith.All I know is what I found on google. But that suggests others have fitted LW-pressure plates to the air-cooled 911 but not to the M96 in the 996 nor the Boxster/Cayman. The only upgrade to the PP frequently mentioned is the Sachs Sport , part # 88 3082 999 754 for just under $500.

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Something like this book takes a lot of time to prepare and honestly my biggest challenge has been the decisions regarding what should be included in the book. Lots of pages and photos were decided to be left out, but they were replaced with other information that was more pertinent and wouldn't create drama on the forums, and other wise. Several times I gave up on even finishing the book. I am not an author, I am a researcher and developer, so mixing what I know in a way that it can be presented, has been quite a challenge. I REFUSE to hand the info to a writer and have them write it, because this is MY book and will be MY way. Whats gotten in the way of finishing the book, has honestly been the book.. What was best for it, and how I should present it. On top of that since I began writing the book I have filed 4 patents, developed a 4.2L DFI engine platform, and lost my Father... It'll be done, when its done. That said... The flywheel HAS nothing to do with engine failure, as supported by the entirety of my research on the matter.

The most important issue is family not cars and flywheels: "and lost my Father..." . Me too and mine was a Royal Engineer not a mere commercial hack like me. I am sure your Dad would be proud to have his family name on the cover of a book that is so eagerly anticipated.

I accept the dismissal of the DMF as a source of rear main bearing failure because of the source of that advice and that it is based on Jake's research-not just a WAG. For the Physics nerds only & with apologies for my disease (Mech Eng) : One of the reasons I had thought a worn+unbalanced DMF could damage both the rear main bearing and the crankshaft is the simple physics of impact . The harmonic balancing of the inherent crankshaft vibrations is a separate subject which is a mystic black art to me. But my connecting rods were way out of balance when I weighed them so that too may be an issue? I am interested in when the crankshaft accelerates & then decelerates quickly . This causes the separate 'halves' of the DMF accelerate and decelerate even more. When the lagging half 'catches up' with the other ,it collides with a buffer-as designed by LUK. Impacts from the DMF structure are transmitted to the rear of the c/s and the rm/bearing. Those impacts are what concerned me. When the rotational freeplay of the DMF is within specification and the DMF balanced , the impact can be absorbed without damage to the c/s or rmb. But what happens when the rotational freeplay of the DMF is double the maximum specified (mine was double!)? Some worn DMFs also have axial wobble(mine did not). Luk may have calculated this impact as 'Kg.m/second'. Obviously the Kgm/s factor in the impact equation has one constant = mass(kg) the weight of the DMF+clutch assy. But it has two variable factors in the worn DMF scenario - the meters & the seconds. The very worn DMF (like mine) travels double the maximum distance(m) specified and it travels for twice the time(?) -"s" . If the buffers in the DMF are not of the specified durometer, even more of this increased impact may also be transmitted. So the impact force of the worn DMF on the connected parts will be increased by a significant factor ?An unbalanced DMF+clutch assy. will also increase this impact. Here is a Porsche related link from deep in total geekdom! https://www.physicsforums.com/thread...t-force.58010/ So perhaps Jake's conclusion is correct but only for a DMF within wear specifications ? So how do you measure your DMF for wear? Well, with typical teutonic excess: http://www.schaeffler.com/remotemedi...tool_de_en.pdf More simply -here is the specification for freeplay and tooth count by part number: http://www.schaeffler.com/remotemedi...list_de_en.pdf

When a dual mass flywheel fails, the engine will start throwing random misfire codes and behaving very erratically well before the failure of the second mass would cause internal engine component failure. The factory M96 engine is very loosely dynamically balanced. On my balancer it typically takes 3-4 hours to balance one rotating and reciprocating mass. The 37.5# DMF and its dampening characteristics allowed the factory to build a "loose" engine and it still run very smoothly. FWIW- a 50 year old unmolested 356 engine is about 2X tighter balanced than a factory M96 engine. Yes, I have the tool that you have provided the link for, and it works very well when precisely measuring all aspects of the DMF for wear. Its not a cheap divide, and its also not very easy to use in the proper manner.

Amazing ! -in many ways. Happy Thanksgiving Jake! Without your guidance I would have abandoned this M96 rebuild project long ago.