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GT4
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PostPosted: Thu Jul 07, 2011 1:35 am    Post subject: What REALLY breaks your IMS & contributes to bearing str Reply with quote

[EDITED AS BAZ DOESN'T LIKE THE TITLE - HE IS CONFUSED BY CAUSE AND EFFECT]

I have been asked if it is better for a M96 or M97 engines (that's the standard 986,996,987.1 and 997.1 blocks) to run high viscosity oils, like 10w40.

And the short answer is no.

The reason is the favourite bête noir of the water-cooled flat sixes - the IMS (intermediate shaft).

Excluding the new Gen 2 MA.01 and MA.02 DFI engines, which cleverly circumvent this issue by not having an IMS!

The M96/M97 are VERY oil hungry, but only thin oil hungry.

The oil not only lubricates and cools as in any engine, but it also runs some very important systems:
    Hydraulic tappets (for valve control from the cams)
    Variocam (all models - eg 996 3.4/3.6) hydraulic chain tensioners (for valve timing control, must be in equilibrium to balance IMS)
    VariocamPlus (later models - eg 996 3.6) hydraulic cam lobe actuation (for valve range control)


The later VariocamPlus requires far more oil for its hydraulic actuated systems than Variocam only.

Low oil levels and low oil pressure (at idle when the engine is hot) can result in some or all systems inside the engine being starved of oil.

Lack of oil to these systems (which control the valves etc) will at best cause increased component wear and reduced operating life, at worth their destruction and ensuing catastrophic engine failure.

It is the oil pump at the end of the IMS that puts the biggest rotational stress on the IMS. However, ironically, it is the oil pump that actuates the Variocam system that needs to be supplied with equal, stable and sufficient oil and oil pressures to prevent IMS imbalances (lateral stress) and bearing stresses!

Ignore all the numerous IMS and IMS bearing and IMS seal modifications that Porsche made over the years (three just during the 996's lifetime, two more in the 997's lifetime, not including its final removal).

None of these fixed the problem: they were attempting to cure for IMS stresses, not a prevention of them.

The THREE most probable reasons that could cause IMS failure are:

1) Manufacturing fractures to bearing/bearing cage or shaft - this is "discovered" quite quickly during the engines life and is almost instant in its failure mode. Usually only affects one batch of bearings or shafts. IMS failures have spanned a DECADE. This is not likely to represent a common cause over time. Under German and US laws Porsche would have to document the issue to the relevant TuV/DoT regulators. No such documents have been filed.
2) Out of balance shaft due to manufacturing or build alignment - this would cause the bearings to rapidly wear, wear unevenly and eventually collapse. However, the noise created by an out of balance IMS would be unmistakably evident on start up. The engine would run badly as the valve timing would-be out and would trigger the DME to illuminate the CEL (engine warning) to full emergency FLASH mode (warning of impending disaster). This would allow an observant driver enough time to turn off the engine before it explodes. Again, if this were to occur, once the engine had been returned to Porsche and investigated, under German and US laws Porsche would have to document the issue to the relevant TuV/DoT regulators. No such documents have been filed.
3) Lack of engine oil to hydraulic systems - this is caused by both true low oil, the wrong oil and instantaneous low oil (starvation) during start-up, high hydraulic use and high-G cornering etc. This is the most likely cause of the intermediate bearing collapse. This is NOT to be confused with the oil (grease) in or not in the IMS ball-races, this is the hydraulic and general oil system the IMS pumps and uses to balance itself (or at least without, becomes imbalanced).

(3) has no other cause other than the owner or driver's use or abuse.

Porsche partially recognised this oil significance and bumped up the 996 crankcase capacity by another 6% (0.5 litres) in MY1999 and also modified the bearing housing (this is in addition to the three 996 direct IMS mods).

So, the oil should always be filled to the brim (so to speak), we know that (and can handily check from the driver's seat without even pulling the dipstick, you have no excuse!).

But what oil?

Well Porsche is pretty specific and unequivocal about this: 0w40.

Yes, it is thin and, yes, that means it can leak (especially with an old or ill fitting RMS), but to not bother getting to the cause and rectifying seals and gaskets or simply tightening block bolts etc by bodging with a thicker (non-leaky) oil is inexcusable.

The "0w" in that code means it is exceptional thin when cold.

This is when the engine is at most stress, the pump is at most stress, the engine is unlubricated, all those hydraulic systems (tappets, Variocam, VariocamPlus etc) are all unpressurised and ineffective.

So help it out: the "0w" (low viscosity oil) will operate all its hydraulic systems as quickly as possible and get around the engine quicker and hence reduce your start-up wear.

Most importantly, when it comes to the IMS, the super thin "0w" will be less stress on the pump at the end of the shaft and will balance the Variocam tensioners across the IMS quicker, and hence reduce IMS bearing stress.

Because of all this, DON'T rag it cold either, or even "warm", wait until it is good and hot (at operating temp and oil pressure <2 bar at idle), then the oil is even thinner. That oil pressure gauge is saying how much stress the pump and IMS are under. Try to minimise it.

In the words of Swiss Tony:
"Driving a Porsche is like making love to a beautiful woman - make sure she's hot and wet before the rough stuff" (or something like that)

Here is the IMS and the oil pump, and the Variocam tensioners and the VariocamPlus cam control and the valves etc etc:



Last edited by GT4 on Fri Jul 08, 2011 1:07 pm; edited 1 time in total
 
  
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michelin
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PostPosted: Thu Jul 07, 2011 7:13 am    Post subject: Reply with quote

What an absolutely superb description !
You are 911uk's mastermind GT4
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Gibbo205
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PostPosted: Thu Jul 07, 2011 7:27 am    Post subject: Reply with quote

Its great reading and all makes sense.

What is your thoughts on 5W-40 oil though?

Mike at Sports & Classic uses 5W-40, LN Engineering have done extensive research to show its also better.

So we can see 10W-40 is a no, but how about 5W-40 as LN engineering seem to have several articles on how this is superior to 0W-40 in heaving improved wear properties etc.

I am still using 0W-40 but was contemplating on moving to 5W-40 on my next oil change considering how it is recommended for models especially with an IMS.
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Chief
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PostPosted: Thu Jul 07, 2011 7:42 am    Post subject: Reply with quote

I totally disagree with you on this on GT4.......

This is what Swiss Tony would say.....

Of course, As you know, I'm a very keen fisherman myself. You know, I've often thought that going fishing was very much like making love to a beautiful woman. First of all, clean and inspect your tackle, carefully pull back your rod cover, and remove any dirt or gunge that may have built up whilst not in use. Then, extend your rod to its full length, and check that there are no kinks or any wear. Particularly at the base, where the grip is usually applied. Make sure you've got a decent float, the appropriate bait, and that there's plenty of shot in your bag.
 
  
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GT4
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PostPosted: Thu Jul 07, 2011 8:03 am    Post subject: Reply with quote

I bloody hate fishing!

Sat there all day with your rod hanging out, not even a nibble!
 
  
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GT4
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PostPosted: Thu Jul 07, 2011 8:34 am    Post subject: Reply with quote

Gibbo205 wrote:
Its great reading and all makes sense.

What is your thoughts on 5W-40 oil though?

Mike at Sports & Classic uses 5W-40, LN Engineering have done extensive research to show its also better.

So we can see 10W-40 is a no, but how about 5W-40 as LN engineering seem to have several articles on how this is superior to 0W-40 in heaving improved wear properties etc.

I am still using 0W-40 but was contemplating on moving to 5W-40 on my next oil change considering how it is recommended for models especially with an IMS.


Firstly, let me make one thing clear in the next description: oil is a complex thing, but the two numbers in its basic description are its cold (Winter) temp properties (viscosity) and hot/operating temp properties (viscosity).

0w40 is thiner at cold ("0w") than 5w40 ("5w")
All things being equal:
0w40 ("40") is identical to 5w40 ("40") at operating temp.

I don't dispute a thicker oil is a better lubricant (in a wear prevention sense), of course in a facilitating movement sense, not so helpful.

From a wear point of view, ideally you would have a treacle thick oil to centralise the pistons as they run the cylinder, forcing it away from the thrust surface, and a treacle thick oil would IN THEORY leave a lovely undisplaced film all over the engine for an extended period of time.

But this is not reality, as (hopefully) every time you start your car up it is to take for nice long run, so that "Xw" is irrelevant almost immediately it begins to warm up, and certainly any time after the first 10-15 mins of driving once operating temp is reached, then just the "40" counts.

Don't forget oil only gets thinner as it gets hotter too, so what sense does that make to depend on its temporary low temp wear characteristic?

Once you do park up, the oil is still hot, so a "40" oil of any description will return to the sump just as fast, so the surface lining properties of a "Xw" are not relevant either.

I also am confused why you would want a thicker oil that takes longer to get any where and takes a lot more effort (stress and BHP sapping) to push it there.

Yes, it gives you lots of instantaneous oil pressure (which on the face of it looks comforting on the oil pressure gauge, and does a great job of hiding any pump wear or other losses), but this is an illusion. Worse, it is irrelevant if that recorded pressure is not actually in the required hydraulic systems as it hasn't got there yet!

The instantaneous pressure of water when you dive bomb it is high, but it ain't going anywhere fast.

Ignoring all that, the best 5w40 can be described as is a compromise between theoretical wear prevention and oil pressure stresses.

Guess what, with no oil any where in the engine at start-up, it doesn't really matter, what matters is how quickly it gets to where it is needed, not how long it "sticks" there (that's what the continuous pump is for). At operating temp "Xw" is long forgotten.

Bottom line is: if you use a thin oil and are worried it isn't protecting your mechanical parts from wear when cold, then just be kind when your mechanical parts are cold!

Once everything is fully lubricated and all the parts have nicely warmed and reached their operating design tolerances (ie stabilised at the intended clearances due to thermal expansion), then go play!
 
  
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PostPosted: Thu Jul 07, 2011 10:06 am    Post subject: Reply with quote

I added comments in iallic but it will not transfer to this system - so my comments start with "BAZ" and my copy of GT4's comments with "GT4"

BAZ I have been impressed with much of what GT4 has written in the past – a good provider of generally accurate information and I have respected his contribution. I am really sorry therefore to feel it necessary to comment on this posting – which is so misleading I am gob smacked. .

GT4 I have been asked if it is better for a M96 or M97 engines (that's the standard 986,996,987.1 and 997.1 blocks) to run high viscosity oils, like 10w40.


BAZ My answer is YES

GT4 The reason is the favourite bête noir of the water-cooled flat sixes - the IMS (intermediate shaft).

BAZ Air cooled flat sixes have one and it has proven perfectly OK – the only difference is that in those it is not a ball bearing on the shaft shrouded from an oil supply but a shell bearing (like big ends and main bearings – force fed oil.

GT4 Excluding the new Gen 2 MA.01 and MA.02 DFI engines, which cleverly circumvent this issue by not having an IMS!

GT4 The M96/M97 are VERY oil hungry, BAZ but only thin oil hungry Because the bores go oval and increase tolerances while the piston temperature then goes up and the recommended oil is then too thin for that scenario.

GT4 The oil not only lubricates and cools as in any engine, but it also runs some very important systems:
Hydraulic tappets (for valve control from the cams)
Variocam (all models - eg 996 3.4/3.6) hydraulic chain tensioners (for valve timing control, must be in equilibrium to balance IMS)
VariocamPlus (later models - eg 996 3.6) hydraulic cam lobe actuation (for valve range control)

GT4 The later VariocamPlus requires far more oil for its hydraulic actuated systems than Variocam only.

GT4 Low oil levels and low oil pressure (at idle when the engine is hot) can result in some or all systems inside the engine being starved of oil.
BAZ Really – come on GT4 is there anyone out there that thinks it is better to run with low oil and low oil pressure?

GT4 Lack of oil to these systems (which control the valves etc) will at best cause increased component wear and reduced operating life, at worth their destruction and ensuing catastrophic engine failure.

BAZ Does anyone need this explaining and what has it to do with the IMS bearing failures?

GT4 It is the oil pump at the end of the IMS that puts the biggest rotational stress on the IMS. However, ironically, it is the oil pump that actuates the Variocam system that needs to be supplied with equal, stable and sufficient oil and oil pressures to prevent IMS imbalances (lateral stress) and bearing stresses!

BAZ Not had a problem though with the pump or shaft.

GT4 Ignore all the numerous IMS and IMS bearing and IMS seal modifications that Porsche made over the years (three just during the 996's lifetime, two more in the 997's lifetime, not including its final removal).

GT4 None of these fixed the problem: they were attempting to cure for IMS stresses, not a prevention of them.

BAZ All the above relates to the IMS (or intermediate shaft). While much of it is reasonably accurate it is irrelevant because this is not what fails – it is the bearing that fails – and the reasons for that failure have nothing whatever to do with the shaft (otherwise how come all the ones we modify have never had a subsequent failure?).

BAZ Remember we are not really interested in the IMS failure – only why the bearing fails.

BAZ There are a few reasons for the failures.
BAZ The bearing starts out filled with grease and sealed to prevent oil getting in. The bearings are an interference fit and some are so tight that they run initially very hot (because the grease is trapped and has higher viscosity) and grinds off a lot of small “running in”particles and while the heat melts the grease (which exits the bearing) that remaining grease and small metal particles turns into a mixture like grinding paste and wears out the internals.
BAZ The pressure on the outer cage from the bearing being too tight can metal fatigue the cage which splits.
BAZ The wear and heat wear through the ball cage which splits in two halves allowing the balls to crowd together. When they do this the mating faces of the balls run against each other in opposite directions (vreating more wear and heat) while the centre of the shaft runs slightly off to one side. The heat generated is much higher than normal. Eventually the hard surface of the bearing is compromised and results in complete failure.
If a bearing started out loose enough to avoid this problem - the heat generated is less and the loss of grease slower and by the time the grease is running out the seal has worn enough to allow a small amount of oil to penetrate into the bearing to lubricate it (and there is oil being sprayed at high velocity by 2 chains right next to that bearing housing (like a chain running @ 40mph in an oil bath) and the pressure from the splash of that oil will get inside the bearing once the seal has worn a bit. Hence usually if the bearing lasts for say 60K – it may go on for the same amount of time again.
BAZ In view of my explanation – the following padding seems just a lot of hot air about nothing very much at all.

GT4 Manufacturing fractures to bearing/bearing cage or shaft - this is "discovered" quite quickly during the engines life and is almost instant in its failure mode. Usually only affects one batch of bearings or shafts. IMS failures have spanned a DECADE. This is not likely to represent a common cause over time. Under German and US laws Porsche would have to document the issue to the relevant TuV/DoT regulators. No such documents have been filed.

BAZ How come then that we can re-use the same shaft with modified bearing parts with complete success once we remove the silly seal that causes most of the problems?.

GT4 2) Out of balance shaft due to manufacturing or build alignment - this would cause the bearings to rapidly wear, wear unevenly and eventually collapse. However, the noise created by an out of balance IMS would be unmistakably evident on start up. The engine would run badly as the valve timing would-be out and would trigger the DME to illuminate the CEL (engine warning) to full emergency FLASH mode (warning of impending disaster). This would allow an observant driver enough time to turn off the engine before it explodes. Again, if this were to occur, once the engine had been returned to Porsche and investigated, under German and US laws Porsche would have to document the issue to the relevant TuV/DoT regulators. No such documents have been filed.

BAZ An out of balance shaft would not put any valve timing out (only a complete beraring failure does this once it has failed) – nothing would be triggered - just load the bearing a little more radially than a well balanced one.

GT4 3) Lack of engine oil to hydraulic systems - this is caused by both true low oil, the wrong oil and instantaneous low oil (starvation) during start-up, high hydraulic use and high-G cornering etc. This is the most likely cause of the intermediate bearing collapse. This is NOT to be confused with the oil (grease) in or not in the IMS ball-races, this is the hydraulic and general oil system the IMS pumps and uses to balance itself (or at least without, becomes imbalanced).

BAZ This has nothing to do with it in a standard grease filled bearing with the seal still in place since replenished oil is not what it is using for lubrication.
Yes – low or no oil will not help any lubricated system to survive but this is just a smoke screen.

GT4 (3) has no other cause other than the owner or driver's use or abuse.

BAZ There is no use or abuse I can think of that will have any influence on the IMS bearing unless it is to drive with low or no oil so the other parts of the engine suffer and add load and heat to the IMS bearing that way.

GT4 Porsche partially recognised this oil significance and bumped up the 996 crankcase capacity by another 6% (0.5 litres) in MY1999 and also modified the bearing housing (this is in addition to the three 996 direct IMS mods).

BAZ None of which achieved anything because they all retain the seal.

GT4 So, the oil should always be filled to the brim (so to speak), we know that (and can handily check from the driver's seat without even pulling the dipstick, you have no excuse!).

BAZ I cannot argue with that.

GT4 But what oil? Well Porsche is pretty specific and unequivocal about this: 0w40.
Yes, it is thin and, yes, that means it can leak (especially with an old or ill fitting RMS), but to not bother getting to the cause and rectifying seals and gaskets or simply tightening block bolts etc by bodging with a thicker (non-leaky) oil is inexcusable. The "0w" in that code means it is exceptional thin when cold.

BAZ But this is only because if it was thicker when the engine was newer it would be more difficult to get into the seal and lubricate the bearing – which of course simply removing the seal does very nicely.

GT4 This is when the engine is at most stress, the pump is at most stress, the engine is unlubricated, all those hydraulic systems (tappets, Variocam, VariocamPlus etc) are all unpressurised and ineffective.

BAZ The engine is at most stress at peak revs and full throttle – in this condition the oil delivery is at the maximum oil pressure the oil pressure relief valve allows and all systems are receiving the maximum oil delivery in volume and pressure possible.

GT4 So help it out: the "0w" (low viscosity oil) will operate all its hydraulic systems as quickly as possible and get around the engine quicker and hence reduce your start-up wear.

BAZ But as clearances increase (this is what wear is) a thinner oil is less effective and seeps out of the gaps left when the car is parked up resulting in less oil on start up (which is when most wear takes place).

GT4 Most importantly, when it comes to the IMS, the super thin "0w" will be less stress on the pump at the end of the shaft and will balance the Variocam tensioners across the IMS quicker, and hence reduce IMS bearing stress.

BAZ Only when new but once the tensioner seals wear and shafts wear they leak quite a lot and this reduces the pressure on the tensioners – so a thicker oil actually leaks less and preserves pressures better. The main stress to the bearing is the result of the cams having large bumps (or lobes) on them and clattering into tappets, valves and springs 12 times every 2 * revs creating tension changes in the chains and hydraulic tensioners and transmitting this down to the sprocket which is therefore subjected to continuous acceleration and deceleration and therefore torque.

GT4 Because of all this, DON'T rag it cold either, or even "warm", wait until it is good and hot (at operating temp and oil pressure <2 bar at idle), then the oil is even thinner. That oil pressure gauge is saying how much stress the pump and IMS are under. Try to minimise it.
The IMS is under greater stress if the delivered oil pressure is higher at higher revs -

BAZ but all the other parts are more likely to wear if the running oil pressure is below maximum (which it is at low revs) – it is not the shaft we are worried about – but the bearing which is not pressure fed anyway.

GT4 In the words of Swiss Tony:
"Driving a Porsche is like making love to a beautiful woman - make sure she's hot and wet before the rough stuff" (or something like that)

BAZ I cannot argue with that but intend to test out the theory - again!.

GT4 Here is the IMS and the oil pump, and the Variocam tensioners and the VariocamPlus cam control and the valves etc etc:

BAZ IN CONCLUSION I think I could have probably written GT4’s report if I was instructed to write an article to deflect attention from the true situation, weave a lot of true but completely irrelevant points into it (to gain the nod of readers as they plod through it) and generally try and make it seem that it was just one of those things. I reads like an employee asked to write a whitewash story full of basically true but practically irrelevant points that provide a smoke screen to the real cause of the problem – the idiotic decision (IMHO) to fit a seal to shroud the bearing from a cool and refreshed oil supply (which the actual bearing manufacture also commented in the same light to me). It was brilliantly executed too – FULL OF TECHNICAL ISSUES THAT ARE ALMOST RIGHT OR RIGHT BUT HAVE NOTHING TO DO WITH THE PROBLEM OR THE SOLUTION, but I find it hard to believe that GT4 has not read my reports before (detailing all the above) and I suspect that he already knows that after fitting the same basic bearing to shafts that are not too tight on the interference fit, with a stronger spindle – but no seal – there has never been any problem whatsoever – and this in itself is the ultimate proof that the only problem is with that silly seal and the consequences. Even without a seal - when the car is left standing the groove in the bearing is vertical so retains oil in the bottom so there is always oil there on start up.

Sorry to disagree GT4 – I simply could not allow such a lot of misleading stuff be recorded as the oracle on the subject without putting in my point of view (surely you already knew I would).

We all have an opinion – many differ – mine is from the point of view of a qualified design engineer and engine designer of previous merit and performance that has found a simple explanation and solution that has works 100 % and is currently responsible for the rebuilding of one engine/day and therefore not only probably sees more failures than anyone else Worldwide – but also provides the most satisfactory proof that his diagnosis and solution is right.

Baz
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GT4
Nordschleife
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PostPosted: Thu Jul 07, 2011 10:35 am    Post subject: Reply with quote

I will fully answer your points when I get time (as they are quite involved), but your understandable obsession with the bearing design ignores the forces that mean that the bearing design is not up to the job.

In any case, this was not meant as a description of IMS or IMS bearings per se, but the affect of low oil or the wrong oil (as per OP's question to me).

If the bearings are shot, 0w40 or 10w40 ain't going to make them better.

However, Pumping 0w40 WILL produce less start-up stress on any already damaged/defective bearings over 10w40 and ultimately the 0w40's very annoying seepage qualities will actually assist as 0w40 will be more likely to penetrate the ball-races than 10w40.

Just a final point that did jump out at me, you oddly mad a comment ref low oil:

Quote:
GT4 Low oil levels and low oil pressure (at idle when the engine is hot) can result in some or all systems inside the engine being starved of oil.
BAZ Really – come on GT4 is there anyone out there that thinks it is better to run with low oil and low oil pressure?


Apparently so, they may not be 911UKers, but many people drive around without checking their oil, or even worse with a warning light on!

Come on, you must see most of them!
 
  
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Gibbo205
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PostPosted: Thu Jul 07, 2011 12:14 pm    Post subject: Reply with quote

Hi there

My understanding is 0W-40 is too thin especially for a UK climate.

As everyone has rightly said, the first number is how thick the oil is when cold, when an oil gets colder it thickens and visocity increases.

This is why in very cold climates 0W and even below is recommended, places such as the Arctic/Canada.

However in the UK we simply don't see such cold temperatures, apart from maybe the extremes of Scotland, a typical winter for the UK is no colder than -10c which even a standard 10W-40 will cope just fine with.

I've always thought the reason Porsche use 0W-40 is more due to the fact it helps reduce emmissions and fuel consumption from what I've read as such giving them better statistics.

From my research and understanding of oils I firmly believe our engines would be better protected, especially the IMS bearing if a high quality 5W-40 oil was used and the oil was changed every 5000-6000 miles would help prevent a failure of the IMS bearing.

I suspect a 5W-40 oil will lubricate the engine from cold just as quick as a 0W-40 oil simply because our UK climate is not cold enough. Yes if we were in sub freezing conditions then 0W-40 would be more suitable.

I think both Baz/GT4 have valid points and it shall be interesting reading but I am still leaning on moving to 5W-40 (probably Motul) and changing the oil every 5000 miles and I have the newer IMS, but I still would take preventive action than having to possibly have it fail and pay the expense of a repair or new engine.
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PostPosted: Thu Jul 07, 2011 12:46 pm    Post subject: Reply with quote

very interesting
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PostPosted: Thu Jul 07, 2011 12:59 pm    Post subject: Reply with quote

GT4 - I am really sorry to have taken this on because you usually are so helpful and provide interesting answers usually quire rightly. I don't like arguing with those I respect on here but on this occasion - something is all wrong - and I cannot understand why - you are too clever to be pushing out this sort of stuff and I DON'T BELIEVE THAT YOU THINK IT IS RIGHT EITHER.

Please explain that IF the bearing is not up to the job - why then can we fit a new bearings of the same specification, not re-fit a seal, fit a stronger spindle (just because the old one is so weak in design it is a disgrace breaking all the notch rules for metal fatigue failure taught at colleges and universities Worldwide) and find that ever since they have all performed perfectly - hundreds of them? despite the fact that we are fitting them to older engines with worn parts in some areas (where customers do not want or cannot afford to replace all of them) and they still work just fine. If it is all to do with oil, toraional stress, revs, owners etc - how come just removing the seal fixes it?

Remember the other end just runs as a plain shaft running in an aluminium hole. I agree it only has one chain that end (not two) but that never gives any problems and being the other end of the same shaft has all the same torsional loadings as its opposite end.

I think your logic is misplaced on this and our experiences prove ours works and works better than the original design - for basically just replacing the same bearing without a seal. We even replaced the double row bearing with the single row one fitted to later cars (which is actually slightly stronger due to deeper tracks) together with a spacing kit and they are all OK too.

The proof of a solution is in the experience of it working or not - it works when the seal is removed - it doesn't if it stays in place.

My comment was sarcastic - sorry - but in the light of all the pading - I thought it a little obvious to state that it is better to have oil in the engine than not. I am sure that even those that run around with low oil know that and they didn't let their oil run low because they think it is OK - they just don't think or couldn't care less. For me it was stating the very obvious - somethingwe could all do and fill pages of answers - to no ones benefit.

Thin oil when hot also sqeezes out of all the tensioners and tappetts quicker (under the load from engaged tappetts and chain tension) than thicker oil - so when you switch off - loses more oil and pressure and on start up renders the car with more work to do to fill and support the loads. Tickover loads are negligible and by the time most people are motoring their cavities are full anyway and the car is running on full pressure.

Where did you get these explanations from - are they your own assessment or are you reading it from something someone else wrote on the subject?

Furthermore - If thin oil is so good why do all racing engines run thicker oil?

Even furthermore - if piston clearances new are OK for thin oil - after say 40K when they have increased by about 0.1mm - by what logic can the same oil be the best?

Usually - it is a difficult situation to criticise Porsche when their reputation was so good. Even when they made other errors that tuners fix - the general public are often sceptical about the solutions that small businesses provide (even though they are usually right). But in the case of these engines - with known problems with IMS bearings, "D" chunk failures, scored bores and pistons etc by what standards or logic can a conslusion be reached that they are always right when small businesses with comparatively limited resources can quickly see the p roblem and provide a solution that is proven to work and solve the problem and on that basis - from which stand point can anyone argue they are wrong and Porsche was right and if so why should any other of their publicity about oil grades and IMS failure causes be given any credence?

Did you also read my recent point reproducing all the benefits claimed by Porsche for their closed deck Mk2 997 engine design and my comment as to why - in that case - if it is so good - was it not fitted to the earlier models manufactured for 13 years when we managed to do so to the very first engine we saw - having imediately identified the problem.

If we can see a problem that they did not and fix it - why - when it comes to the IMS bearing - all of a sudden are Porsche right about it all and not us - especially when ours works and theirs often didn't?

You don't need to waste time replying on this - you got it wrong mate - you cannot win your argument - and the best thing to do is let it drop and pick up on something else where your input is usually so valuable.

One failure against so many good and valuable postings is not something to worry about.


Baz
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PostPosted: Thu Jul 07, 2011 1:11 pm    Post subject: Reply with quote

Gibbo205 wrote:
Hi there

My understanding is 0W-40 is too thin especially for a UK climate.

As everyone has rightly said, the first number is how thick the oil is when cold, when an oil gets colder it thickens and visocity increases.

This is why in very cold climates 0W and even below is recommended, places such as the Arctic/Canada.

However in the UK we simply don't see such cold temperatures, apart from maybe the extremes of Scotland, a typical winter for the UK is no colder than -10c which even a standard 10W-40 will cope just fine with.

I've always thought the reason Porsche use 0W-40 is more due to the fact it helps reduce emmissions and fuel consumption from what I've read as such giving them better statistics.

From my research and understanding of oils I firmly believe our engines would be better protected, especially the IMS bearing if a high quality 5W-40 oil was used and the oil was changed every 5000-6000 miles would help prevent a failure of the IMS bearing.

I suspect a 5W-40 oil will lubricate the engine from cold just as quick as a 0W-40 oil simply because our UK climate is not cold enough. Yes if we were in sub freezing conditions then 0W-40 would be more suitable.

I think both Baz/GT4 have valid points and it shall be interesting reading but I am still leaning on moving to 5W-40 (probably Motul) and changing the oil every 5000 miles and I have the newer IMS, but I still would take preventive action than having to possibly have it fail and pay the expense of a repair or new engine.


So, your OK March to November, but chancing it December to February?

Seems entirely sensible.

The oil is not like a switch, once over 0 degress it's thin.

Any thicker oil will continue to be relatively thicker through the entire temperature range until it hits the same "40" viscosity at operating temp.

I really don't see what downside there is to have it thinner at cold, afterall, it will only get even thinner any way once in use (warmed up).

As I said (may have been the other thread), it is still more important to have full oil than perhaps the exact oil.
 
  
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PostPosted: Thu Jul 07, 2011 1:18 pm    Post subject: Reply with quote

bazhart wrote:
GT4 - I am really sorry to have taken this on because you usually are so helpful and provide interesting answers usually quire rightly. I don't like arguing with those I respect on here but on this occasion - something is all wrong - and I cannot understand why - you are too clever to be pushing out this sort of stuff and I DON'T BELIEVE THAT YOU THINK IT IS RIGHT EITHER.

Please explain that IF the bearing is not up to the job - why then can we fit a new bearings of the same specification, not re-fit a seal, fit a stronger spindle (just because the old one is so weak in design it is a disgrace breaking all the notch rules for metal fatigue failure taught at colleges and universities Worldwide) and find that ever since they have all performed perfectly - hundreds of them? despite the fact that we are fitting them to older engines with worn parts in some areas (where customers do not want or cannot afford to replace all of them) and they still work just fine. If it is all to do with oil, toraional stress, revs, owners etc - how come just removing the seal fixes it?

Remember the other end just runs as a plain shaft running in an aluminium hole. I agree it only has one chain that end (not two) but that never gives any problems and being the other end of the same shaft has all the same torsional loadings as its opposite end.

I think your logic is misplaced on this and our experiences prove ours works and works better than the original design - for basically just replacing the same bearing without a seal. We even replaced the double row bearing with the single row one fitted to later cars (which is actually slightly stronger due to deeper tracks) together with a spacing kit and they are all OK too.

The proof of a solution is in the experience of it working or not - it works when the seal is removed - it doesn't if it stays in place.

My comment was sarcastic - sorry - but in the light of all the pading - I thought it a little obvious to state that it is better to have oil in the engine than not. I am sure that even those that run around with low oil know that and they didn't let their oil run low because they think it is OK - they just don't think or couldn't care less. For me it was stating the very obvious - somethingwe could all do and fill pages of answers - to no ones benefit.

Thin oil when hot also sqeezes out of all the tensioners and tappetts quicker (under the load from engaged tappetts and chain tension) than thicker oil - so when you switch off - loses more oil and pressure and on start up renders the car with more work to do to fill and support the loads. Tickover loads are negligible and by the time most people are motoring their cavities are full anyway and the car is running on full pressure.

Where did you get these explanations from - are they your own assessment or are you reading it from something someone else wrote on the subject?

Furthermore - If thin oil is so good why do all racing engines run thicker oil?

Even furthermore - if piston clearances new are OK for thin oil - after say 40K when they have increased by about 0.1mm - by what logic can the same oil be the best?

Usually - it is a difficult situation to criticise Porsche when their reputation was so good. Even when they made other errors that tuners fix - the general public are often sceptical about the solutions that small businesses provide (even though they are usually right). But in the case of these engines - with known problems with IMS bearings, "D" chunk failures, scored bores and pistons etc by what standards or logic can a conslusion be reached that they are always right when small businesses with comparatively limited resources can quickly see the p roblem and provide a solution that is proven to work and solve the problem and on that basis - from which stand point can anyone argue they are wrong and Porsche was right and if so why should any other of their publicity about oil grades and IMS failure causes be given any credence?

Did you also read my recent point reproducing all the benefits claimed by Porsche for their closed deck Mk2 997 engine design and my comment as to why - in that case - if it is so good - was it not fitted to the earlier models manufactured for 13 years when we managed to do so to the very first engine we saw - having imediately identified the problem.

If we can see a problem that they did not and fix it - why - when it comes to the IMS bearing - all of a sudden are Porsche right about it all and not us - especially when ours works and theirs often didn't?

You don't need to waste time replying on this - you got it wrong mate - you cannot win your argument - and the best thing to do is let it drop and pick up on something else where your input is usually so valuable.

One failure against so many good and valuable postings is not something to worry about.


Baz


I think I covered the fact my post does not vouch for the bearing quality or not, but only the affect of oil viscosity on the system the bearing is in.

Yes, my nan could do with a new heart valve, but instead of the cost and risk associated with a cure, she just doesn't run up and down stairs.

All owners who have an M99/97 engine have the IMS risk, my advice is just to help preserve it before is needs open Hart surgery.
 
  
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PostPosted: Thu Jul 07, 2011 1:31 pm    Post subject: Reply with quote

GT4 wrote:
bazhart wrote:
GT4 - I am really sorry to have taken this on because you usually are so helpful and provide interesting answers usually quire rightly. I don't like arguing with those I respect on here but on this occasion - something is all wrong - and I cannot understand why - you are too clever to be pushing out this sort of stuff and I DON'T BELIEVE THAT YOU THINK IT IS RIGHT EITHER.

Please explain that IF the bearing is not up to the job - why then can we fit a new bearings of the same specification, not re-fit a seal, fit a stronger spindle (just because the old one is so weak in design it is a disgrace breaking all the notch rules for metal fatigue failure taught at colleges and universities Worldwide) and find that ever since they have all performed perfectly - hundreds of them? despite the fact that we are fitting them to older engines with worn parts in some areas (where customers do not want or cannot afford to replace all of them) and they still work just fine. If it is all to do with oil, toraional stress, revs, owners etc - how come just removing the seal fixes it?

Remember the other end just runs as a plain shaft running in an aluminium hole. I agree it only has one chain that end (not two) but that never gives any problems and being the other end of the same shaft has all the same torsional loadings as its opposite end.

I think your logic is misplaced on this and our experiences prove ours works and works better than the original design - for basically just replacing the same bearing without a seal. We even replaced the double row bearing with the single row one fitted to later cars (which is actually slightly stronger due to deeper tracks) together with a spacing kit and they are all OK too.

The proof of a solution is in the experience of it working or not - it works when the seal is removed - it doesn't if it stays in place.

My comment was sarcastic - sorry - but in the light of all the pading - I thought it a little obvious to state that it is better to have oil in the engine than not. I am sure that even those that run around with low oil know that and they didn't let their oil run low because they think it is OK - they just don't think or couldn't care less. For me it was stating the very obvious - somethingwe could all do and fill pages of answers - to no ones benefit.

Thin oil when hot also sqeezes out of all the tensioners and tappetts quicker (under the load from engaged tappetts and chain tension) than thicker oil - so when you switch off - loses more oil and pressure and on start up renders the car with more work to do to fill and support the loads. Tickover loads are negligible and by the time most people are motoring their cavities are full anyway and the car is running on full pressure.

Where did you get these explanations from - are they your own assessment or are you reading it from something someone else wrote on the subject?

Furthermore - If thin oil is so good why do all racing engines run thicker oil?

Even furthermore - if piston clearances new are OK for thin oil - after say 40K when they have increased by about 0.1mm - by what logic can the same oil be the best?

Usually - it is a difficult situation to criticise Porsche when their reputation was so good. Even when they made other errors that tuners fix - the general public are often sceptical about the solutions that small businesses provide (even though they are usually right). But in the case of these engines - with known problems with IMS bearings, "D" chunk failures, scored bores and pistons etc by what standards or logic can a conslusion be reached that they are always right when small businesses with comparatively limited resources can quickly see the p roblem and provide a solution that is proven to work and solve the problem and on that basis - from which stand point can anyone argue they are wrong and Porsche was right and if so why should any other of their publicity about oil grades and IMS failure causes be given any credence?

Did you also read my recent point reproducing all the benefits claimed by Porsche for their closed deck Mk2 997 engine design and my comment as to why - in that case - if it is so good - was it not fitted to the earlier models manufactured for 13 years when we managed to do so to the very first engine we saw - having imediately identified the problem.

If we can see a problem that they did not and fix it - why - when it comes to the IMS bearing - all of a sudden are Porsche right about it all and not us - especially when ours works and theirs often didn't?

You don't need to waste time replying on this - you got it wrong mate - you cannot win your argument - and the best thing to do is let it drop and pick up on something else where your input is usually so valuable.

One failure against so many good and valuable postings is not something to worry about.


Baz


I think I covered the fact my post does not vouch for the bearing quality or not, but only the affect of oil viscosity on the system the bearing is in.

Yes, my nan could do with a new heart valve, but instead of the cost and risk associated with a cure, she just doesn't run up and down stairs.

All owners who have an M99/97 engine have the IMS risk, my advice is just to help preserve it before is needs open Hart surgery.



But your advice is going against what others have said.

The advice to preserve the IMS is to use 5W-40 instead of 0W-40 and perform more frequent oil changes.

Your saying its better to use 0W-40, wheras Hartech, LN Engineering amongst others say 5W-40 is better.

So the question is who is right?

You do realise an oil such as 5W-40 has more wear prevention than say a 0W-40 oil yes?

As its the bearing in the IMS which is the issue, its all about preventing the wear of that bearing, which a 5W-40 does better than a 0W-40, yet your suggesting otherwise.

Also I did not suggest using different oils during Summer/Winter here in the UK, our climate is not cold enough to warrant using such thin oils and I am fully aware oil is not like a switch as such why in the UK as our winters are rather mild and our summers just warm the same oil all year round is fine. But in more extreme climates they either run a thinner oil or change to a thinner oil for winter.
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PostPosted: Thu Jul 07, 2011 4:57 pm    Post subject: Reply with quote



Please not another oil debate
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PostPosted: Thu Jul 07, 2011 5:06 pm    Post subject: Re Reply with quote

So once again....which oil should we be using!???? (gen1 carrera s)
 
  
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PostPosted: Thu Jul 07, 2011 5:11 pm    Post subject: Reply with quote

Gibbo205 wrote:
GT4 wrote:
bazhart wrote:
GT4 - I am really sorry to have taken this on because you usually are so helpful and provide interesting answers usually quire rightly. I don't like arguing with those I respect on here but on this occasion - something is all wrong - and I cannot understand why - you are too clever to be pushing out this sort of stuff and I DON'T BELIEVE THAT YOU THINK IT IS RIGHT EITHER.

Please explain that IF the bearing is not up to the job - why then can we fit a new bearings of the same specification, not re-fit a seal, fit a stronger spindle (just because the old one is so weak in design it is a disgrace breaking all the notch rules for metal fatigue failure taught at colleges and universities Worldwide) and find that ever since they have all performed perfectly - hundreds of them? despite the fact that we are fitting them to older engines with worn parts in some areas (where customers do not want or cannot afford to replace all of them) and they still work just fine. If it is all to do with oil, toraional stress, revs, owners etc - how come just removing the seal fixes it?

Remember the other end just runs as a plain shaft running in an aluminium hole. I agree it only has one chain that end (not two) but that never gives any problems and being the other end of the same shaft has all the same torsional loadings as its opposite end.

I think your logic is misplaced on this and our experiences prove ours works and works better than the original design - for basically just replacing the same bearing without a seal. We even replaced the double row bearing with the single row one fitted to later cars (which is actually slightly stronger due to deeper tracks) together with a spacing kit and they are all OK too.

The proof of a solution is in the experience of it working or not - it works when the seal is removed - it doesn't if it stays in place.

My comment was sarcastic - sorry - but in the light of all the pading - I thought it a little obvious to state that it is better to have oil in the engine than not. I am sure that even those that run around with low oil know that and they didn't let their oil run low because they think it is OK - they just don't think or couldn't care less. For me it was stating the very obvious - somethingwe could all do and fill pages of answers - to no ones benefit.

Thin oil when hot also sqeezes out of all the tensioners and tappetts quicker (under the load from engaged tappetts and chain tension) than thicker oil - so when you switch off - loses more oil and pressure and on start up renders the car with more work to do to fill and support the loads. Tickover loads are negligible and by the time most people are motoring their cavities are full anyway and the car is running on full pressure.

Where did you get these explanations from - are they your own assessment or are you reading it from something someone else wrote on the subject?

Furthermore - If thin oil is so good why do all racing engines run thicker oil?

Even furthermore - if piston clearances new are OK for thin oil - after say 40K when they have increased by about 0.1mm - by what logic can the same oil be the best?

Usually - it is a difficult situation to criticise Porsche when their reputation was so good. Even when they made other errors that tuners fix - the general public are often sceptical about the solutions that small businesses provide (even though they are usually right). But in the case of these engines - with known problems with IMS bearings, "D" chunk failures, scored bores and pistons etc by what standards or logic can a conslusion be reached that they are always right when small businesses with comparatively limited resources can quickly see the p roblem and provide a solution that is proven to work and solve the problem and on that basis - from which stand point can anyone argue they are wrong and Porsche was right and if so why should any other of their publicity about oil grades and IMS failure causes be given any credence?

Did you also read my recent point reproducing all the benefits claimed by Porsche for their closed deck Mk2 997 engine design and my comment as to why - in that case - if it is so good - was it not fitted to the earlier models manufactured for 13 years when we managed to do so to the very first engine we saw - having imediately identified the problem.

If we can see a problem that they did not and fix it - why - when it comes to the IMS bearing - all of a sudden are Porsche right about it all and not us - especially when ours works and theirs often didn't?

You don't need to waste time replying on this - you got it wrong mate - you cannot win your argument - and the best thing to do is let it drop and pick up on something else where your input is usually so valuable.

One failure against so many good and valuable postings is not something to worry about.


Baz


I think I covered the fact my post does not vouch for the bearing quality or not, but only the affect of oil viscosity on the system the bearing is in.

Yes, my nan could do with a new heart valve, but instead of the cost and risk associated with a cure, she just doesn't run up and down stairs.

All owners who have an M99/97 engine have the IMS risk, my advice is just to help preserve it before is needs open Hart surgery.



But your advice is going against what others have said.

The advice to preserve the IMS is to use 5W-40 instead of 0W-40 and perform more frequent oil changes.

Your saying its better to use 0W-40, wheras Hartech, LN Engineering amongst others say 5W-40 is better.

So the question is who is right?

You do realise an oil such as 5W-40 has more wear prevention than say a 0W-40 oil yes?

As its the bearing in the IMS which is the issue, its all about preventing the wear of that bearing, which a 5W-40 does better than a 0W-40, yet your suggesting otherwise.

Also I did not suggest using different oils during Summer/Winter here in the UK, our climate is not cold enough to warrant using such thin oils and I am fully aware oil is not like a switch as such why in the UK as our winters are rather mild and our summers just warm the same oil all year round is fine. But in more extreme climates they either run a thinner oil or change to a thinner oil for winter.


I think I answered that the first time you asked, two or three posts up the page Confused

And the answers still stand.

A thicker oil will stop wear, a thicker oil will require more force and power to move around and be slower to move around.

You pays your money and takes your choice.

I choose to protect my IMS at start up and take care not to wear it out by not loading the engine before it fully lubricates, actuates and reaches operating temp (where "Xw" has no bearing anyway).

I don't think I made any statements about the frequency of oil changes.

I did however make the point you MUST keep it topped up (to some extent irrespective of grade).

The whole point was the optimum way to run the hydraulic systems: that
requires a lot of oil (ie brimmed) and requires oil as quick as possible.

Last edited by GT4 on Thu Jul 07, 2011 5:12 pm; edited 1 time in total
 
  
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PostPosted: Thu Jul 07, 2011 5:11 pm    Post subject: Reply with quote

Ground nut oil is very good on Trim so I'm told Very Happy
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PostPosted: Thu Jul 07, 2011 5:19 pm    Post subject: Reply with quote

tea Grey

Apart from careful warming up from cold, regular oil changes(every 5/6k) the thermostat upgrade, regular rad cleaning(+ coolant flush every 20k) and using good quality oil to prevent IMS failure, it's a bit of a lottery which car gets this issue.

btw £166m up for grabs in the lottery. Win that and you won't give a damm about IMS failures Laughing
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PostPosted: Thu Jul 07, 2011 6:21 pm    Post subject: Reply with quote

GT4 I have been asked if it is better for a M96 or M97 engines (that's the standard 986,996,987.1 and 997.1 blocks) to run high viscosity oils, like 10w40.

BAZ My answer is YES

10w40, you're kidding, right?

GT4 The reason is the favourite bête noir of the water-cooled flat sixes - the IMS (intermediate shaft).

BAZ Air cooled flat sixes have one and it has proven perfectly OK – the only difference is that in those it is not a ball bearing on the shaft shrouded from an oil supply but a shell bearing (like big ends and main bearings – force fed oil.

Almost all cars have an "IMS" (or layshaft). The engines on a 993 and 996 are so similar, you're kidding right?

GT4 Low oil levels and low oil pressure (at idle when the engine is hot) can result in some or all systems inside the engine being starved of oil.
BAZ Really – come on GT4 is there anyone out there that thinks it is better to run with low oil and low oil pressure?

Apparently this was a joke Dont know

GT4 Lack of oil to these systems (which control the valves etc) will at best cause increased component wear and reduced operating life, at worth their destruction and ensuing catastrophic engine failure.
BAZ Does anyone need this explaining and what has it to do with the IMS bearing failures?

Not sure if this is meant as a joke too, but how many people owning a 9X6, 9X7 know how the hydraulic tappets, Variocam and VariocamPlus work and what they depend on for their efficacy and longevity?

GT4 It is the oil pump at the end of the IMS that puts the biggest rotational stress on the IMS. However, ironically, it is the oil pump that actuates the Variocam system that needs to be supplied with equal, stable and sufficient oil and oil pressures to prevent IMS imbalances (lateral stress) and bearing stresses!

BAZ Not had a problem though with the pump or shaft.

frustrated I must be speaking Mongolian. I never said there was a problem with the shaft or pump, just that they are what the shaft drives or what the shaft works against. Additionally, as stated, if the pump fails to feed the oil actuated chain tensioners controlling the cams, then laterall stress may occur across the IMS and/or the timing is (by definition) disrupted.

GT4 Ignore all the numerous IMS and IMS bearing and IMS seal modifications that Porsche made over the years (three just during the 996's lifetime, two more in the 997's lifetime, not including its final removal).

GT4 None of these fixed the problem: they were attempting to cure for IMS stresses, not a prevention of them.

BAZ All the above relates to the IMS (or intermediate shaft). While much of it is reasonably accurate it is irrelevant because this is not what fails – it is the bearing that fails – and the reasons for that failure have nothing whatever to do with the shaft (otherwise how come all the ones we modify have never had a subsequent failure?).

Hmm, I wonder what might be over stressing the (admittedly under engineered) bearings Question
I know, I'll write it all down and post it on the forum.
Just because you can produce an engineering cure, does not preclude trying to implement some prevention


BAZ Remember we are not really interested in the IMS failure – only why the bearing fails.

I wasn't, I was interested in what stresses are put on the IMS (and its bearings), not the bearing themselves. That's why I haven't discussed them, or the multitude of other parts (good or bad) in a 996

BAZ There are a few reasons for the failures.
BAZ The bearing starts out filled with grease and sealed to prevent oil getting in. The bearings are an interference fit and some are so tight that they run initially very hot (because the grease is trapped and has higher viscosity) and grinds off a lot of small “running in”particles and while the heat melts the grease (which exits the bearing) that remaining grease and small metal particles turns into a mixture like grinding paste and wears out the internals.
BAZ The pressure on the outer cage from the bearing being too tight can metal fatigue the cage which splits.
BAZ The wear and heat wear through the ball cage which splits in two halves allowing the balls to crowd together. When they do this the mating faces of the balls run against each other in opposite directions (vreating more wear and heat) while the centre of the shaft runs slightly off to one side. The heat generated is much higher than normal. Eventually the hard surface of the bearing is compromised and results in complete failure.
If a bearing started out loose enough to avoid this problem - the heat generated is less and the loss of grease slower and by the time the grease is running out the seal has worn enough to allow a small amount of oil to penetrate into the bearing to lubricate it (and there is oil being sprayed at high velocity by 2 chains right next to that bearing housing (like a chain running @ 40mph in an oil bath) and the pressure from the splash of that oil will get inside the bearing once the seal has worn a bit. Hence usually if the bearing lasts for say 60K – it may go on for the same amount of time again.
BAZ In view of my explanation – the following padding seems just a lot of hot air about nothing very much at all.

Glad you rolled out yet another speech on bearings again, when I have made no comment on bearings per se.

This time I get to say irrelevant, as that was NOT what the OP asked me about in his PM ref: 0w40 or 10w40.

If you have something to add in the respect of oil grades, I would be grateful.



GT4 Manufacturing fractures to bearing/bearing cage or shaft - this is "discovered" quite quickly during the engines life and is almost instant in its failure mode. Usually only affects one batch of bearings or shafts. IMS failures have spanned a DECADE. This is not likely to represent a common cause over time. Under German and US laws Porsche would have to document the issue to the relevant TuV/DoT regulators. No such documents have been filed.

BAZ How come then that we can re-use the same shaft with modified bearing parts with complete success once we remove the silly seal that causes most of the problems?.

Erm, this list of three "possibilities" were meant as a process of elimination. If you re-read that first paragraph, it is written to conclude NO batch manufacturing fractures to bearing/bearing cage or shaft have been proved. ie you actually agree with the conclusion?

GT4 2) Out of balance shaft due to manufacturing or build alignment - this would cause the bearings to rapidly wear, wear unevenly and eventually collapse. However, the noise created by an out of balance IMS would be unmistakably evident on start up. The engine would run badly as the valve timing would-be out and would trigger the DME to illuminate the CEL (engine warning) to full emergency FLASH mode (warning of impending disaster). This would allow an observant driver enough time to turn off the engine before it explodes. Again, if this were to occur, once the engine had been returned to Porsche and investigated, under German and US laws Porsche would have to document the issue to the relevant TuV/DoT regulators. No such documents have been filed.

BAZ An out of balance shaft would not put any valve timing out (only a complete beraring failure does this once it has failed) – nothing would be triggered - just load the bearing a little more radially than a well balanced one.

Again, this "possibility" is put forward in the process of elimination and is then eliminated on our way to a definitive cause of IMS failure (or at least the most common or probable). So again you actually agree with the conclusion?

GT4 3) Lack of engine oil to hydraulic systems - this is caused by both true low oil, the wrong oil and instantaneous low oil (starvation) during start-up, high hydraulic use and high-G cornering etc. This is the most likely cause of the intermediate bearing collapse. This is NOT to be confused with the oil (grease) in or not in the IMS ball-races, this is the hydraulic and general oil system the IMS pumps and uses to balance itself (or at least without, becomes imbalanced).

BAZ This has nothing to do with it in a standard grease filled bearing with the seal still in place since replenished oil is not what it is using for lubrication.

Yes – low or no oil will not help any lubricated system to survive but this is just a smoke screen.

Never said it did have any affect on the supposed SEALED (or at least the bizarrely intentionally sealed at inception ball-races). This is all about how one grade of oil or another may affect instantaneous stresses on the IMS.

I know the old adage that everything to a man with a hammer looks like a nail, but really, not every question has the answer "defective bearing".


GT4 (3) has no other cause other than the owner or driver's use or abuse.

BAZ There is no use or abuse I can think of that will have any influence on the IMS bearing unless it is to drive with low or no oil so the other parts of the engine suffer and add load and heat to the IMS bearing that way.

OK, so it's the bearing again. I can't argue with that as A) that wasn't the point of my post, B) I am getting tired of all this bearing stuff.

Use and abuse can, oddly, affect ALL the cars systems


GT4 Porsche partially recognised this oil significance and bumped up the 996 crankcase capacity by another 6% (0.5 litres) in MY1999 and also modified the bearing housing (this is in addition to the three 996 direct IMS mods).

BAZ None of which achieved anything because they all retain the seal.

Hmm, Porsche add oil capacity to increase consistency of supply to hydraulic ancilleries and some how that has what to do with an unrelated seal?

GT4 So, the oil should always be filled to the brim (so to speak), we know that (and can handily check from the driver's seat without even pulling the dipstick, you have no excuse!).

BAZ I cannot argue with that.

Thank **** for that!

GT4 But what oil? Well Porsche is pretty specific and unequivocal about this: 0w40.
Yes, it is thin and, yes, that means it can leak (especially with an old or ill fitting RMS), but to not bother getting to the cause and rectifying seals and gaskets or simply tightening block bolts etc by bodging with a thicker (non-leaky) oil is inexcusable. The "0w" in that code means it is exceptional thin when cold.

BAZ But this is only because if it was thicker when the engine was newer it would be more difficult to get into the seal and lubricate the bearing – which of course simply removing the seal does very nicely.

Oh FFS, who brings a bearing to a hydraulic ancillery fight?
Look, Porsche never intended oil of ANY grade to enter your damned bearing as they conciously SEALED it! (and no, I don't want a discussion about how they shouldn't we all know that, and after-market is by definition in hind-sight. But is ISN'T anything to do with oil grade used


GT4 This is when the engine is at most stress, the pump is at most stress, the engine is unlubricated, all those hydraulic systems (tappets, Variocam, VariocamPlus etc) are all unpressurised and ineffective.

BAZ The engine is at most stress at peak revs and full throttle – in this condition the oil delivery is at the maximum oil pressure the oil pressure relief valve allows and all systems are receiving the maximum oil delivery in volume and pressure possible.

Outside of simple heat stresses or friction wear, which obviously occur most at high engine speeds, peak oil pressure is most defininitely an indicator of high stress loads. Guess what, you get 5 bar plus at start-up. All this post was about was using thicker or thinner oil ("Xw") at start-up (not operating temp, as "Xw" has no bearing :doh: then). Did you just say "all systems are receiving the maximum oil delivery in volume and pressure possible", so you want the pump to pump oil to where it is needed as quickly as possible, and you ant the pressure transmitted without viscosity losses Question

If only there were a fast moving, low-viscosity loss oil for use at start-up?


GT4 So help it out: the "0w" (low viscosity oil) will operate all its hydraulic systems as quickly as possible and get around the engine quicker and hence reduce your start-up wear.

BAZ But as clearances increase (this is what wear is) a thinner oil is less effective and seeps out of the gaps left when the car is parked up resulting in less oil on start up (which is when most wear takes place).

Yep, this advice is for un-shagged engines. This is for when they are young, before they develop IMS failure. If the engine has survived long enough to round out, then it has probably gone past the point where the IMS failure we all dread can happen. At that statge everything is just fair wear and tear.

Every post I have every made before has advocated 0w40 as long as the engine is young and tight enough eg:

http://www.911uk.com/viewtopic.php?t=64051
http://www.911uk.com/viewtopic.php?t=60002
http://www.911uk.com/viewtopic.php?t=46081
etc etc


GT4 Most importantly, when it comes to the IMS, the super thin "0w" will be less stress on the pump at the end of the shaft and will balance the Variocam tensioners across the IMS quicker, and hence reduce IMS bearing stress.

BAZ Only when new but once the tensioner seals wear and shafts wear they leak quite a lot and this reduces the pressure on the tensioners – so a thicker oil actually leaks less and preserves pressures better. The main stress to the bearing is the result of the cams having large bumps (or lobes) on them and clattering into tappets, valves and springs 12 times every 2 * revs creating tension changes in the chains and hydraulic tensioners and transmitting this down to the sprocket which is therefore subjected to continuous acceleration and deceleration and therefore torque.

Exactly! Thicker oil is used to hide losses or leaks, not for the benefit of the systems it is supposed to run. 10w40 is for mechanics who can't be bothered to change a seal, gasket, tighten up bolts or simply swap out the old for new.

GT4 Because of all this, DON'T rag it cold either, or even "warm", wait until it is good and hot (at operating temp and oil pressure <2 bar at idle), then the oil is even thinner. That oil pressure gauge is saying how much stress the pump and IMS are under. Try to minimise it.
The IMS is under greater stress if the delivered oil pressure is higher at higher revs -

BAZ but all the other parts are more likely to wear if the running oil pressure is below maximum (which it is at low revs) – it is not the shaft we are worried about – but the bearing which is not pressure fed anyway.

So ignoring the bearing (yet again), are you saying Porsche designed an oil pump that can't pump enough?

Oil is incompressible, it doesn't matter how thick or thin it is, it WILL transfer ALL the pressure everywhere almost instantaneously - that is the point of ALL hydraulic systems, be they the brakes on your car or the rams on a JCB. If, however, if it is thick, it will present FLOW problems.

Again, this is all a smoke screen (as you might put it), as 99% of the time 0w40 = 5w40 = 10w40 = Xw40 as it will be at operating temp. For the first few minutes in every drive I want my oil where it is supposed to be as quickly as possible, everything else is irrelevant.


GT4 In the words of Swiss Tony:
"Driving a Porsche is like making love to a beautiful woman - make sure she's hot and wet before the rough stuff" (or something like that)

BAZ I cannot argue with that but intend to test out the theory - again!.

Floor

GT4 Here is the IMS and the oil pump, and the Variocam tensioners and the VariocamPlus cam control and the valves etc etc:

BAZ IN CONCLUSION I think I could have probably written GT4’s report if I was instructed to write an article to deflect attention from the true situation, weave a lot of true but completely irrelevant points into it (to gain the nod of readers as they plod through it) and generally try and make it seem that it was just one of those things. I reads like an employee asked to write a whitewash story full of basically true but practically irrelevant points that provide a smoke screen to the real cause of the problem – the idiotic decision (IMHO) to fit a seal to shroud the bearing from a cool and refreshed oil supply (which the actual bearing manufacture also commented in the same light to me). It was brilliantly executed too – FULL OF TECHNICAL ISSUES THAT ARE ALMOST RIGHT OR RIGHT BUT HAVE NOTHING TO DO WITH THE PROBLEM OR THE SOLUTION, but I find it hard to believe that GT4 has not read my reports before (detailing all the above) and I suspect that he already knows that after fitting the same basic bearing to shafts that are not too tight on the interference fit, with a stronger spindle – but no seal – there has never been any problem whatsoever – and this in itself is the ultimate proof that the only problem is with that silly seal and the consequences. Even without a seal - when the car is left standing the groove in the bearing is vertical so retains oil in the bottom so there is always oil there on start up.

Sorry to disagree GT4 – I simply could not allow such a lot of misleading stuff be recorded as the oracle on the subject without putting in my point of view (surely you already knew I would).

We all have an opinion – many differ – mine is from the point of view of a qualified design engineer and engine designer of previous merit and performance that has found a simple explanation and solution that has works 100 % and is currently responsible for the rebuilding of one engine/day and therefore not only probably sees more failures than anyone else Worldwide – but also provides the most satisfactory proof that his diagnosis and solution is right.

Baz

OK, so thanks for ending on a, guess what, a bearing note, but I again ask what this has to do with:

Quote:
I have been asked if it is better for a M96 or M97 engines (that's the standard 986,996,987.1 and 997.1 blocks) to run high viscosity oils, like 10w40.
 
  
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