IMS - 2rs + freeze plug
 

All,

Starting a new thread so that the waters are clear.

Was originally going to go with an SKF Hybrid, later determined to be unsuitable, as discussed here:

http://986forum.com/forums/performance-technical-chat/67817-ims-going-skf-hybrid.html

Came up with a theory that the grease washout in the IMS bearing was caused by the "lung effect:"

http://986forum.com/forums/545188-post48.html

So my new plan is as follows:

Acquire dead IMS shaft for testing. Plug the end with a freeze plug, measure that this causes no deformity of shaft. install a pressure gauge on the air space inside, then heat to 300 degrees, see how much pressure we get. Once I have that number, take compressed air and double it to make sure the freeze plug will hold.

then, discard test shaft and install pelican parts bearing, as supplied by Pelican, with the addition of a freeze plug on my vehicle in situ.

At 40k miles pull pelican parts bearing and verify that oil has not washed out the grease, at that time install suitable steel SKF, FAG, NSK bearing of high quality. Thereafter every clutch change.

why?

My theory is that Porsche got the spec of the bearing right, assuming no grease washout. The laws of physics tell me that the "lung effect" (discussed above) is the most likely reason oil and grease are getting exchanged in the bearing. So, if you stop this effect, the bearing Porsche specified will be more than suitable to get from clutch change to clutch change (100k or so miles)

So the permanent (in my mind) IMS method is:

1) install freeze plug in end of IMS shaft, install pelican bearing (uprated bolt is critical)
2) change bearing every time you change clutch (plain steel bearing is like $10, uprated bolt should last through as many clutches and bearings as an engine could go through.)

I am advocating that the IMS problem can be resolved for essentially $3. A freeze plug is the missing component. I have no financial incentive from Pelican Parts or the Freeze plug manufacturers, just a fellow hobbyist with a theory that I intend to prove to be correct.

$185 initial outlay, assuming you can borrow special tools, then an extra $10 every time you change the clutch is a LOT more palatable than thousands especially if it is just as effective at preventing catastrophic engine damage. I actually think a 2rs (double sealed) bearing without thermally caused oil intrusion will be more effective at preventing catastrophe as metal particles will be kept out of the bearing, allowing it to lead its full rated life EVEN IF you end up with metal particle or two in the oil.

If someone asked, I would say that the factory bearing with no freeze plug is highly suspect and should be changed, it almost certainly has oil washout, and is not to be trusted.

regards,

Silber

Do we really need another thread on this?

Just buy the IMS Solution and be done with it.

I second that.

Sorry, that is so expensive they won't even tell you how much it costs. Not going to spend that kind of money on an engine with 114k miles on it.

If you don't want to read my thread, just pass it by.

regards,

Silber

Go for it Silber.

I went with a known IMS solution in my own car because I don't want to worry about it. However, I do enjoy reading these kind of experimental threads. You never know what you can learn.

Hello Silber,

1. as said, there are 3 different IMS shafts available and they are different in detail.
2. you have underpressure in your crank case.
3. the simple freeze plug - in my opinion - can start moving. That is why i said come up with something more sophisticated.

Regards, Markus

Gre
 

Hello Silber
I don't mind reading these type of thread's. I just had a thought about the grease in the bearing, would it not wash out anyway with the heat down there. I wouldn't have thought the grease would have been in there for long, unless it was some type of grease I dont know about. Just a thought.

1. as said, there are 3 different IMS shafts available [B]and they are different in detail

The only part that would need to be the same would be the tube size for my test purposes. Would that be different on all 3?

2. you have underpressure in your crank case.

True, will have to account for that with my testing.

3. the simple freeze plug - in my opinion - can start moving. That is why i said come up with something more sophisticated.

I want to test just how hard it is to move a freeze plug in an IMS shaft, so am going to install one in a test shaft and try to get it to fail. Sometimes the simple solutions are the best, especially if when tested they hold up. I think any other solution will either be a) not as strong, or b) impossible to remove. Freeze plugs are time tested as very strong, and possible to remove.

Regards,

Silber

The seal is supposed to keep the grease in and other stuff out. Even heated liquefied grease should stay in there to some extent. I just wonder why when these are taken apart there is no grease, only oil.

It seems like there has to be some factor other than simple heat that would remove all the grease and substitute oil. Air expands and contracts with heat, this creates pressure in a sealed system, or movement of fluids/gasses in a system with a leak. I think the bearing seals are that leak and the action of the air pulls oil through the bearing over and over washing the grease completely away. Remove the air reservoir and (hopefully) the problem is solved.

I could well be wrong, but most analysis of the IMS looks at the grease washout as a given, and tries to solve the problem from there by throwing fancy bearings at it. I want to go back one step and solve the grease washout problem so the fancy bearing is not needed.

regards,

Silber

Air
 

Hello Silber
I don't think you can remove the air reservoir from a bearing. They are never fully packed with grease, for a number of reasons.
If you look to the other end of the IMS shaft what do you see, a simple plain bearing. Never any problems at that end. Personally I think a plain bearing is the way to go, oil fed of course. I know as well as most there is one on the market
but wouldn't be a big deal for an engineer with a lathe to make one.

The grease is washed out.

If you don't understand why read the SKF brochure i've linked in the other thread. Especially the part with the sealings, contamination, lifetime and so on. OK over all it's 300 pages, but than you'll understand bearings a little more.

The IMS tubes are different in detail, because the used bearings are different. Some have circlip grooves, some not. Also some are for 3 chain and some are for 5 chain engines.

Regards, Markus

Markus, all of the tubes have clip groves cut in them, just in different places and of different sizes depending upon which style bearing is used.

By air reservoir i meant all the air in the ims tube, it is acting as a reservoir of air that sucks oil through the bearing, i believe.

Regards,

Silber

I am just going to test the freeze plug, so will never install a bearing or chain, will never go in an engine. I believe the tube dimensions are common to all styles of shaft.

regards,

Silber

Silber says this is his personal experiment. He is not evangelizing use of his freeze plug. And if you have been around the M96 as long as I have you will have read prior discussion(and rejection) of the freeze plug + ball bearing idea by an expert(not me- although I was the one who asked that specific question).
Let's try to help Silber ? it is like a Jake Raby destruction test without all the instruments and dyno
The Freeze plug dimensions and material choice.
1. How do you define Interference fit?give the 0.0000"
2.Why use plug material with a different coefficient of expansion ?
3. Use Bearing Seal ? High temp Epoxy?
I do hope no destruction occurs !

I expect that Silber has already seen this thread. It runs for about 250 posts and addresses some similar questions. Post #52 actually has a freeze plug in the diagram. It's worth browsing through if you are interested in this topic.

http://986forum.com/forums/performance-technical-chat/49448-another-ims-bearing-thread.html

I had not seen this link, about halfway through reading it, came upon this:

http://986forum.com/forums/425140-post230.html

had not considered the pressure disassembling IMS shaft. Will have to think that one through. At first blush, I don't think the pressures will be high enough, but need to test exactly how high the pressures might be experimentally.

EDIT: the last two posts in the thread seem to indicate the IMS Solution uses a "blanking plate" to block air/oil from the ims shaft tube. Sounds very similar to what a freeze plug does, and would indicate that pressure inside the shaft is not an issue.

All I want to do is make the Porsche bearing last as long as a clutch does reliably. May not be possible. Nothing in that thread rules out that a plug might help the situation, however.

1) Freeze plugs commercially available would seem to be .3mm or .01 inch interference. However since they are sheet metal there will be some deformation.

2) I have changed my mind on this, I think steel plug will hold better and be less prone to impacting anything.

3) am hoping that without the air in the IMS shaft to pressurize and depressurize the bearing, a standard 2RS seal will be enough to make the bearing last as long as a clutch reliably. Pelican parts bearing is rated at 40k, plan to pull it at that time to verify if there is any grease left or it all washed out.

The only real risk I am taking is that a freeze plug will cause my engine to explode. I can rule a lot of that out with destructive testing on a dead IMS shaft. I believe there is a previously sold ims retrofit that used a freeze plug, anyone know more about this?

I appreciate your willingness to experiment and freely share your results. I wish you best of luck and be safe.

I get where your coming from financially. My car has 133K miles and, at 17 years old, the last nine of which have been mine, I've of the opinion that the car owes me nothing. That being said, if I'm still the owner when the car needs a clutch, I'll replace the bearing.

My math is kind of like this....
Current value of car: $7.5K
Value as a roller (worst case):$2.5K
Spending $1500-$2,000 to just go ahead and replace the bearing seems like very expensive insurance.

Please understand that I'm all for the bearing change with a clutch. I sleep well at night not worrying about this thing although I do find the discussions worth reading.

OK, let's talk about the expansion of air.

And sorry i have to calculate in the metric system, because i'm too stupid to do it in the imperial system.

If we have 1 litre of air = 1000 cm3 and we heat it up 10 degree celsius it will expand 37 cm3 with every 10 degree celsius more.

So lets say the ims shaft has a volume of 1 litre (i'm retty shure it's more) and we heat it up from 0 degree celsius to 200 degree celsius as a max, value (i would say the max. should be between 120 and 150 degree celsius in the IMS area). So calculate worst case 200 degree celsius and that would mean we have an expansion of 740 cm3.

p1 = 10^5 Pa
V1 = 0.1m^3
T1 = 0° = 273K
V2 = 0.174m^3
T2 = 200° = 473K
p2 = ?

p2 =

p1 * V1 * T2 | 10^5 Pa * 0,1 m^3 * 473 K | 4730000 | 99574 Pa
--------------- = -------------------------------- = ---------- =
T1 * V2 | 273 K * 0,174 m^3 | 47,502 |

99574 Pa = 0,99574 Bar = 14,4 PSI

To compare that. The recommended 986 front tyre pressure is 2.0 Bar.

Atmospheric pressure will be set as a constant of 1 Bar at normal ground.

Additionally in a crank case we have a low pressure system. That means we have negative pressure. And that means we are below 1 Bar atmospheric pressure.

Next would be to calculate the right volume for the IMS tube so you can calculate the right pressure at a given temperature.

Personally i think that would be a lot of atmospheric pressure for a simple freeze plug in a rotating and vibrating IMS tube. Also i suspect the volume in an IMS tube is much higher. And remember the freeze plug has to stay in place and you have to prevent additional unbalancing.

Regards, Markus

PS: i don't know if there is any way to show the formula in a better way. If i open it in the editor it looks good. But if i click save it looks goofy.

Keep up the good work Silber ,New ideas are great for all .
An idea , if you want the pressure in the ims tube to equalize either negative or positive, with the pressure on the other side of the bearing , just punch a SMALL hole in the sealing cap inside the hex drive at the oil pump end of the shaft . This is what the EPS folk suggest as an oil feed for their roller bearing conversion , although they do groove the hex drive as well. General leakage will take care of the equalization which is what you want
Peter

I really like the freeze plug idea. Don't know ok if the pressures work out but it sounds like a cost effective way around the problem. Also gets around the problem of having an open bearing.

Markus, your posts are always so exceptionally helpful, thank you for all your input on this!

14.4 psi is almost ideal for a freeze plug. Automotive cooling systems usually are designed to operate at a pressure of between 14 and 15 psi. Freeze plugs are designed to stay put and hold pressure in this application, I would assume there is a wide margin of safety, but will be testing to make sure.

I still plan to do some research to find out what the previous retrofit was that used one and what happened with peoples engines.

Silber

But freeze plugs are hammered in to a cast iron block usually. Very different from a flimsy sheet metal IMS tube

Here's some photographic proof that it's been done before, the ones that did it was a company called Casper.

http://986forum.com/forums/526229-post29.html

IMS solution uses a plug is well, I hear it is patented, but I'm not sure that that would hold up if it's just freeze plug, as it was done before by Casper.

Regards,

Silber

But, that tube is supported by the sprocket casting where are you are driving into it, so essentially you're driving into a casting. The tube will do nothing but be an intermediate layer between the casting and the freeze plug it will not have to support any load.

As soon as I find a dead intermediate shaft I will be testing this.

Silber

It is patented, and is not a freeze plug. And the "Casper" system was a failure....

It would be a lot more helpful to say why it was a failure.

This sample calculation was done by using 1 litre as the inner volume of the tube and a max. temperature of 200 degrees Celsius. As said, the volume will be higher. So measure an IMS tube and recalculate. I suspect the pressure will be much higher than 14,4 PSI, because i think the inner volume of the IMS tube higher.

Besides that in a crankcase you have a negative pressure, but in an closed IMS tube you have positive pressure – as said before.

So the freeze plug handles negative pressure, not positive pressure. So to say it isn't pressed to the outside, it is sucked in. ;)

And if you have 14 psi negative pressure in a crankcase and you have 14 psi positive pressure in the IMS tube, the pressure difference is 28 PSI.

Casper Labs IMS: just do a google search. ;)

Regards, Markus

This ancient history thread explains some of the twists an turns in this story and mentions Casper:
Different Approach to DIY IMSB Retro / Parts and Pics
The problem with the freeze plug idea is the interference fit,the tool to install it, the lubricant(Bearing Seal?) -the issue is not axial of course.It is linear. If you force a very tight freeze plug into flimsy tube and it goes in like some RMS seals do,so you push harder ......
Try to adapt on of the IMSB insertion tools to do this gently & square ?
Recall that the IMS tubes are often oor so that may complicate the interference issue.
* Why do you think most IMSB kits use 1RS and no plug ?
Even the kits designed by JR and sold by LN. And those guys know all about the freeze plug concept. They deliberately do not use it with ball bearings but they do with the plain bearing. The cost issue is trivial.

I have googled Casper labs, and their IMS retrofit.

It seems like they just sort of disappeared, I haven't been able to find any reports of failures, or any other reason why they apparently stopped existing.

Silber

In that case, I'll try to fill in the blanks for you: Bill Ryan of Casper (who were involved in aircraft components) came out of nowhere in late 2011, claiming to have a "low cost alternative to the over priced LN ceramic bearing" (the Casper kit sold for around $325). They cobbled together a kit using an off the shelf ceramic bearing, a center bolt either from Pelican or reuse your own (was never really clear on this), a plugged shaft, and which used the OEM flange from your original bearing. They sold a couple of kits off fleabay, which apparently did not fare very well, and they folded their tent in the IMS retrofit market in early 2012. End of story.........

I am thinking this is not a problem, freeze plugs are often used in oil galleries and oil pressure can be higher than that.

I cannot seem to find any engineering data for freeze plugs on the web as far as what kind of pressures they can hold. I may have to experiment. I have feelers out for a damaged IMS shaft that I can plug and pressure test, hopefully I will find one before too long.

Silber

The problem is not the freeze plug itself, it's the overall situation.

You have an IMS tube that rotates axial, horizontal and vertical at very different frequencies and is accelerated and decelerated. Just think about that this thing is part of the valvetrain and every time the cam moves / hits a valve it vibrates a little bit. Also the IMS tube connects both valvetrains. One in the front and one in the back. So you have torsional forces within the IMS tube.

Next thing is that if the freeze plug starts moving, because the air in the IMS tube expands in worst case it will be pressed against the IMSB main bolt. The freeze plug rotates, the bolt is in a fixed position. Think about if you want that and what can happen to the bolt, screw and plug and in the end to the IMSB and IMS tube. Keep in mind that you have horizontal, vertical and axial forces and vibration. And you have vibration caused by combustion.

If you install the freeze plug like Casper Labs installed their "patented thing", the edge of the freeze plug can rub against the circlip that holds the IMSB in position. This might be a less bad situation as if the plug rubs against the center bolt at first sight. But if the circlip fails, everything will fail sooner or later.

As said before, the problem is to fix the freeze plug or anything else without harming the IMS tube (temperature, expansion levels, balancing, weight, maybe engine oil in the Ims tube to the bearing side) in a defined and fixed position.

That is why i said come up with a more sophisticated solution than a freeze plug. ;)

And to be honest, i did like the freeze plug idea too at first sight, but after thinking of it in detail, i don't think that it is a clever solution. The clever solution would be if you can make 100% shure that the "plug" can't move in any direction, doesn't harm the tube and doesn't cause any balancing problems.

But if you insist on using a freeze plug… it's your car, your engine, your money. ;)

Regards from Germany,
Markus

Casper does not hold the patent, Jake Raby does.

JFP: if you like to have a discussion about patents, laws, country regions… we can do that.

Besides that i think we all know what your interests are.

But i think here we just talk about ideas and if somebody decides to do an individual solution for a personal car. So…

Regards, Markus

My interest is keeping the conversation on point and factually correct...

Some previous freeze plug discussion.

http://986forum.com/forums/performance-technical-chat/59365-ims-bearing-upgrade-6.html

Silber