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GT4
Nordschleife
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Joined: 08 Nov 2008
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PostPosted: Fri Jan 20, 2017 2:45 pm    Post subject: Reply with quote

Whisper it, but the Mezger had an IMS (in name)

It has to do that the cams are run at the right speed.

The problem with the M96/M97 was yet another cost cutting/production efficiency.

Porsche started with a beautiful and conventional engineering solution, incorporating a continuous clean, fresh, cool oil-fed plane bearing one end, and then the tea-break klaxon sounded, and they popped a (mostly) sealed, greased ball-race not dissimilar to a BMX bike bearing on the other.

Both ends drive symmetric cam systems, both get symmetric oil pressure tensioners, both sides get symmetric forces and torque stresses.

But the bearings aren't symmetric ... and then they wonder why the poor thing imbalances itself to death or simply seizes, cracks or jumps a sprocket and lunches the valves into the pistons when the end with the ball-race overheats or its bearing grease leaks out.
 
  
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GT4
Nordschleife
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PostPosted: Fri Jan 20, 2017 2:48 pm    Post subject: Reply with quote

Alfaian wrote:
Well put baz; question for you- mines an early 2005 3.8 S with the smaller bearing and it's parked on my driveway which is fairly steep with the nose facing down. Am I right in thinking the ims bearing is swathed in luxurious millers 10w50 nano while it's parked up?

Just a thought and thanks in advance

Thumb


I might start an internet rumour.

You'll know when it's taken, as people will be popping their Porsches in inversion beds at night Bandit

 
  
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Alfaian
Imola


Joined: 12 Mar 2014
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Location: S.wales


PostPosted: Fri Jan 20, 2017 2:50 pm    Post subject: Reply with quote

bazhart wrote:
It also results in a physically smaller cam box sprocket and saves space which is desperately needed when you have two cylinder heads opposed and big tyres to squeeze in.

It reduces the speed of the oil pump as well (although that may not be a good thing).

Ball bearings usually retain oil in the carriers for a long time after running but even if parked up - the ball track in the IMS bearing is a groove internally in the vertical plane so the groove will always have some oil in it whatever way the car is parked and the oil splash is generated before the engine even fires up - so no need to worry about parking angles etc.


Baz


Cheers baz Thumb I can cancel the sleeping tablets for the time being Smile

GT4 - behave yourself man Smile
 
  
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Palladium
Indianapolis


Joined: 01 Nov 2015
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PostPosted: Fri Jan 20, 2017 2:58 pm    Post subject: Reply with quote

so my 1982 has one, why dident they just copy that one?
 
  
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Alex
Le Mans
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Joined: 06 Mar 2014
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Location: The Ribble Valley, Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Fri Jan 20, 2017 3:22 pm    Post subject: Reply with quote

Palladium wrote:
so my 1982 has one, why dident they just copy that one?


As GT4 states - cost cutting.
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Carrerascott
Silverstone


Joined: 28 Mar 2015
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PostPosted: Fri Jan 20, 2017 6:16 pm    Post subject: Reply with quote

So what is the best solution for my Dec 2004 C2S with the small IMS bearing ..... Dont know
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Clanky
Österreich


Joined: 24 Aug 2012
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2007 Porsche 997 Turbo

PostPosted: Fri Jan 20, 2017 6:18 pm    Post subject: Reply with quote

alex yates wrote:
DucatiRob wrote:
alex yates wrote:
+1!

Absolute nonsense


Not so sure it is nonsense, all bearings need some form of constant lubrication but in my opinion it is overly complicated when just removing the seal does essentially the same job, plus no more moving parts required!

Gutted for the OP!


The inside of a car engine is the equivalent of standing in a washing machine full of oil. The spray & vapour gets everywhere and the faster it spins - the more lubrication of all parts.


In most cases yes, but (Correct me if I'm wrong Baz) the IMS bearing is inside the IMS which is designed as a sealed tube, & therefore not designed to be filled with oil & splash lubricated.
I read somewhere, & it might even have been on Hartech's blog, about some of the failed bearings found to have had the grease washed out by the crankcase oil which had seeped in past the seals.

I'm all for the idea of removing the seals providing there is enough lubrication after the grease has inevitably washed out, hence the idea of the forced feed, but even that would need the IMS vented in some way to allow the flow to return to the sump.

If you only remove the seals, then after the grease has gone, where can you expect the oil to get in to lubricate the bearing if the shaft is still sealed?
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Alex
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PostPosted: Fri Jan 20, 2017 7:34 pm    Post subject: Reply with quote

The shaft and bearing is submerged below oil when the engine isn't running. The outer side of the bearing is fully exposed to whats going on in the engine so gets enough lubrication (as it doen't need much being a frictionless bearing unlike a solid one) to function correctly.

As for Porsche designing the ims.......that was the problem......they didn't. It's a crazy concept putting a dust shielded grease filled bearing submerged in oil. Even the bearing manufacturer advised Porsche of that. Obviously they didn't listen.
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timbo1811
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Joined: 13 Dec 2016
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PostPosted: Fri Jan 20, 2017 7:53 pm    Post subject: Reply with quote

My local Indy has seen many IMS failures and have replaced some without a bearing failure and all of them had the grease washed out and were relying on oil which had seeped in. When they replace a bearing now they remove the grease seal and have had no issues so far.
As for early 997's having either the small or large bearing, apparently its almost impossible to tell without eyeballing it, at least with the smaller bearing it can be replaced with engine in situ, ok if your fitting a clutch, but as I have a tip not such what to do either.
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Floydsolo
Monza


Joined: 04 Sep 2015
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PostPosted: Fri Jan 20, 2017 8:05 pm    Post subject: Reply with quote

For any potential buyers out there....Not all Early 2005 have the small bearing. Check the engine number to be sure.
 
  
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DucatiRob
Albert Park


Joined: 22 Jul 2015
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2006 Porsche 997 Carrera 2S

PostPosted: Fri Jan 20, 2017 8:27 pm    Post subject: Reply with quote

Floydsolo wrote:
For any potential buyers out there....Not all Early 2005 have the small bearing. Check the engine number to be sure.


I believe that the larger bearing was fitted to the MY2006 cars which were shipped around October 2005. Somewhere on here is a thread where you can check the engine number for when it was upgraded.
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Floydsolo
Monza


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PostPosted: Fri Jan 20, 2017 8:30 pm    Post subject: Reply with quote

Yes just what I said, & mine is a March 2005 with the later bearing.
 
  
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bazhart
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Joined: 20 May 2009
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PostPosted: Sat Jan 21, 2017 10:37 am    Post subject: Reply with quote

Yes a plain bearing (as fitted to earlier 911 variants up to M96 engines) has a pressurised oil feed which all plain bearings need but the ball bearing in the M96/97 IMS can be exposed to plenty of splash oil if the seal is removed.

Oil does seep in if the seal is still there - it can hardly be called an oil seal - OK for dust and thick grease perhaps - but someone seems to have forgotten that the engine temperatures inside would turn the grease thin like oil anyway and eventually seep out.

The shaft is hollow and eventually can fill up with very old smelly and probably carcinogenic oil through the leak in the inner seal.

The inclusion of the seal could be connected to manufacturing storage time as a grease filled sealed bearing has longer shelf life than an open unsealed one? Don't forget the new boss brought in to transform Porsche financially had a washing machine manufacturing background!

All they had to do was pull the outer seal off during assembly! leave the existing grease there and allow it to wash out during running in to be replaced with fresh oil.

The smaller bearings have too thin an outer track to prevent the interference fit from altering the pinch between different shafts, spindles and bearings when the tolerances stack up for a tight fit. The larger bearing has a much stronger thicker outer casing and of course does not require a tighter fit - so sustains the designed clearances better.

On diss- assembly some housings and outer bearing diameters in the smaller bearing show signs of "pick up" during assembly or running and pushing another new bearing in without measuring the housing and correcting any errors can lead to further problems down the line. Bearings have different fits (or tightnesses) in their design and manufacture and we chose a replacement bearing with more clearance to compensate. We may replace a larger bearing on a high mileage engine during reassembly and have not seen "pick-up" there.

Feeding oil from a pressurised feed will not deliver it into the bearing under pressure - just flow - and if it is high flow it would starve/reduce the engine oil delivery on hot tickover when the pressure is low anyway and well below the relief valve setting - so there is nothing you can do about it. Whereas as soon as an engine starts there is a massive amount of oil splashed into the bearing area - after all - if you want some proof - just consider that a high mileage car with the seal still in place and the bearing still OK has managed to lubricate sufficiently after all the grease has gone and just relying on the tiny amount of oil that is managing to splash into it past the slightly worn seals - not being replenished and therefore running hotter than the main oil supply! What more evidence do you need that splash oil without the seal restricting it - is adequate?

Baz
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infrasilver
Fast & Furious
Fast & Furious


Joined: 04 Oct 2010
Posts: 8200
Location: East Midlands

2001 Porsche 996 Targa

PostPosted: Sat Jan 21, 2017 2:18 pm    Post subject: Reply with quote

I fitted a new bearing kit to our washing machine and when I looked at the bearing it looked the same size as my IMS bearing, I got them both side by side and measured with my caliper and they were identical. The washing machine bearing took more load than the IMSB would ever do though, the kit was £30.
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GT4
Nordschleife
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PostPosted: Sat Jan 21, 2017 9:36 pm    Post subject: Reply with quote

Carrerascott wrote:
So what is the best solution for my Dec 2004 C2S with the small IMS bearing ..... Dont know


When you crack the engine/gearbox (e.g. Clutch), just pop an OEM bearing in there with the seals removed.
 
  
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Carrerascott
Silverstone


Joined: 28 Mar 2015
Posts: 121
Location: West Yorkshire


PostPosted: Sat Jan 21, 2017 11:17 pm    Post subject: Reply with quote

So if you order a OEM bearing from Porsche OPC do you get another 'small' version or do you get a 'large' newer one?
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infrasilver
Fast & Furious
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PostPosted: Sat Jan 21, 2017 11:26 pm    Post subject: Reply with quote

Carrerascott wrote:
So if you order a OEM bearing from Porsche OPC do you get another 'small' version or do you get a 'large' newer one?


You can't order one from OPC unless you order the whole IMS, you need to just buy the correct spec bearing from one of the bearing manufacturers.
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bazhart
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PostPosted: Sun Jan 22, 2017 12:38 pm    Post subject: Reply with quote

OK but remember that bearings are manufactured in different specifications even though they are the same overall sizes - and this is relevant to choose the right ones for the application (not necessarily just the most expensive or precise ones).

Baz
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Delanor
Nürburgring


Joined: 01 Oct 2016
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Location: The land of the big cat!


PostPosted: Sun Jan 22, 2017 2:01 pm    Post subject: Reply with quote

infrasilver wrote:
I fitted a new bearing kit to our washing machine and when I looked at the bearing it looked the same size as my IMS bearing, I got them both side by side and measured with my caliper and they were identical. The washing machine bearing took more load than the IMSB would ever do though, the kit was £30.


I really can understand that comparison of bearings. Laughing

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Clanky
Österreich


Joined: 24 Aug 2012
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2007 Porsche 997 Turbo

PostPosted: Sun Jan 22, 2017 6:04 pm    Post subject: Reply with quote

Delanor wrote:
infrasilver wrote:
I fitted a new bearing kit to our washing machine and when I looked at the bearing it looked the same size as my IMS bearing, I got them both side by side and measured with my caliper and they were identical. The washing machine bearing took more load than the IMSB would ever do though, the kit was £30.


I really can understand that comparison of bearings. Laughing

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Del.


LMFAO!
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