JapaDog

Hi guys,

I've been a long time lurker and a new member to the forum. I'm planning to get into an 05-07 911 C2S and am doing as much research as i can to understand more on the car.

I've did quite a bit of research in regards to the RMS and IMS problem and from the general consensus, most people agree that, due to the beefier IMS bearing on the MY06+ car, owners of MY06 cars seem to less likely to encounter the IMS failure problem.

I've read quite in depth into the IMS article posted by LN engineering and through reading it, I've come to a few questions specifically regarding to the articles:

"On a new or remanufactured engine built in or after MY06 utilizing the revised M97 IMS, the only "preventative" measure that can be taken short of our retrofit kits is to remove the seal off the front of the IMS bearing, to allow for engine oil to lubricate the bearing"

How difficult is it for a shop to perform such modification? can this be done at the same time when replacing the clutch?

And here comes the question relating a possible turbo upgrade in the future. Keep in mind though I'm not very mechanically savy and do apologize for my ignorance,

"Computer simulation of the 6204 bearing showed that only three ***** are under load at any given time. Hertz stress is moderate. Lube film thickness is very small. Ideally it should be greater than the worst surface finish. Speed is not high enough to develop an elastohydrodynamic film to overcome surface finish/film issue. Fatigue life is high due to relative light load but with no EHD film there will be metal/metal contact and wear. With only three ***** under load at any one time the unloaded ***** will be dragged around by the ball separator. When a ball leaves the loaded zone it will tend to be driven into the separator pocket."

Now, in according to the previous paragraph, does it imply that, with a higher intermediate shaft rpm, the increased speed would be high enough to increase the elastohydrodynamic film formation in lessening the effect of surface contact, that such phenomenon then reduce the wear of the roller ***** inside the bearing, and hence we come to the conclusion that when we drive it like we stole it, the IMS tends to have a lesser chance of failing?

and if such speculation is correct, does it mean that, if tpc turbocharge upgrade is to be considered in the future, this upgrade would not necessarily cause the IMS bearing to fail faster because a higher horsepower engine would cause the IMS rpm to be higher?

Of course, I understand that adding a turbo charge into an N/A engine will stress other part of the engine shortening the general engine life span.

I know that I'm overreacting here but hope to fully educate myself as much as I can in all the preventative actions. I hope you guys can understand~~

Spiffyjiff

i'm not sure i understood more than 1/2 of what you typed but i'll give you a few brief thoughts nonetheless.

when i went to a talk given by charles from LN, i learned that apparently it's basic "ball bearing 101" logic that the faster it spins, the less stress it's under.

as far as a turbo/SC conversion goes - let's face it, the engine was not "specifically designed" for that. does that mean it shouldnt be done? maybe. does that mean it cant be done safely and with minimal negative impact to the engine? of course not. anything can be done. and with the right shop doing the work and/or with proven products, you lessen the risk significantly. BUT there's still that risk.

i'm sure all the the turbo/SC dealers and installers out there will stand by their work and products - TPC included. but the bottom line remains, despite some of them having outstanding skills and working knowldge of these cars, they might not have the research history or a test population big enough to be sure beyond a shadow of a doubt that it's "completely safe". does this make them in the wrong to tell you it's safe? absolutely not. they've done their homework and they believe in their products and services. hell, take the IMS issue that even you bring up. porsche believed in the 996 and 997 engines but despite all the experience and skill, and all the countless hrs of R&D, they still put a ("unofficially"!!) weak component in their top of the line model. who knows, maybe internally they had their doubts about the product, but the issue wasn't really brought to the forefront until "customer testing" began and engines started failing.

all that said, it doesnt hurt to arm yourself with all the research you can but at the end of the day we live in the real world where scientific proof rules. find folks who have gotten a turbo/SC conversion and see what, if any, problems or issues they've had.

FWIW, if i ever decide to bolt on some HP, i will go to TPC as well.

i'm sure this didnt help, but i'm done rambling nonetheless.

Palmbeacher

a)Not very difficult, b) Yes





I disagree with the conclusion, not to mention the completely anecdotal data sampling from which it is extrapolated. The IMS shaft turns at only 2/3 the speed of the engine. An engine running at 2K vs 7K amounts to only a difference of 3K rpm of the IMS. That would not increase EHD film enough to significantly affect the longevity of the bearing.

A more plausible explanation as to why engines run consistently at higher RPMs might see less IMS bearing failure is this: The bearing was designed to be packed with bearing grease and sealed. Thus the internal specifications of the bearing are designed to accomodate the thickness of grease, vs oil. Also, the bearing placement is such that it does not receive copious amounts of oil splash. Once the seal breaks down, small amounts of oil seep in and wash out the grease. Now the ***** have more slop, plus the dirty oil contains grit and turns acidic, leading to both mechanical and chemical wear of the bearing.

Higher engine RPMs force more oil to the bearing, and exchange it more frequently, thus potentially prolonging the bearing life.

NOTE: That ONLY can happen if the seal is not intact.

Removing the seal if it has been breached would allow better oil inflow and outflow, which is good. However, it still doesn't lubricate as well as the grease for which the bearing was designed...therefore, removing an intact seal would actually be worse for the bearing. It makes sense only because of the cost involved in getting at the bearing. If it was an easy job, it would make much more sense to check it periodically and only remove the seal once it was determined to be ineffective.

The LN bearing is made specifically with materials that better withstand less than adequate lubrication.

JapaDog

Thank you for all the replies!

Now that the IMS seal issue has been clarified, here comes another question. What are some of the symptoms when the ims seal starts failing? As I understand that on a MY05 car, all you have to do is to have a shop to replace the ims bearing to the LN bearing and that would resolve the whole problem. However, what would you do if you caught your MY06 car's ims start failing? is engine assembly the only way out on this?

The reason the IMS bearing worries me so much on a MY06+ car is due to the fact that, according to the LN articles, the bearing cannot be extracted independently like an MY05 car, and when it does fail or starts to fail, an engine reassembly is needed to change the bearing, seems like a very pricey solution.

Like I said, I might have been overreacting, but an MY05 car + LN bearing seems like a better solution down the road than having an MY06+ car with bearing that cannot be serviced. Or, is my logic faulted?

RollingArt

The correct answer is VERY difficult. You'd need to open the motor to even see the bearing seal. That's the problem.

I don't think you're very clarified just yet. You may need better opinions than this band of internet experts has to offer.

Don't be to quick to drink the LN cool-aid. He and Jake want everyone who'll listen and pay attention to buy an '05 car and then buy the bearing retrofit. The evidence of '06 and up cars blowing their IMS just isn't there. Tony Callas of Callas Motorsport had an IMS thread going here once upon a time. Jake Raby had joined in to help fuel the flames. At one point Tony asked Jake if he had ever seen an '06 M97 motor with an IMS failure. Jake mysteriously disappeared, never answered the question and the thread faded away. Hmmm- draw your own conclusions.






Phil

RollingArt

One final thought.

Just buy a 997 turbo car. Totally different engine, starting with the crankcase. No IMS shaft and it's designed from the crankshaft to the spark plugs to be a real turbo motor. Plus you get a stouter transmission, bigger brakes, better cooling...

Think about it.





Phil

Spiffyjiff

actually, i think that's incorrect. it is "relatively" easy to change the seal, just not the bearing. the seal can be removed/changed "simply by" separating the trans/motor etc - as you would when changing a pre-05 IMS - and removing the IMS cover to get to the seal. but the redesigned '06+ bearing is too big to fit thru the hole (that's what she said) and thus the need to open the motor itself to extract and change the actual bearing.

or a GT3.

JapaDog

Thank you for the input RollingArt,

as you can probably tell from my reply, as much as the MY05 + LN bearing seems to make more sense in the long run, I'm leaning more over to the MY06 cars, hence I've come to the question, is an engine reassembly inevitable if the bearing does fail.

Ynot

justatoy and cattman from 6speedonline are guys you want to talk to if you are thinking about forced induction. I'm not mechanically inclined either. But I do drive a TPC turbo C4S, it has about 5K miles with the TPC turbo, it's been flawless. Drive very normal, until you petal to the metal. MarathonBob (also from 6speedonline) daily his C2 without any issues. TPC is a great company, guys there are very friendly and willing to assist with any problems you might have. Life is too short to worry about problems, if you are worried get a CPO one, then buy extended warranty when CPO expires.

JapaDog

Ynot:

Definitely, I'm on 6speed too and I just happen to live very close to justatoy. Both Justatoy and Cattman are the people that gave me great confidence that FI on the M97 can be reliable.

racer

Typically, when the bearing fails, the shaft moves and the engine is destroyed. From what I've read, these motors get "replaced", not rebuilt in the traditional sense.

JapaDog

From what I've heard, if an inspection is done every 30,000 miles or when the clutch is replaced, mechanics can probably pick up the symptoms that the bearing is failing before the engine is destroyed.

According to the LN article, before the bearing should fail complete, there should be a slight movement on the stud that shows the bearing isn't firmly holdng the stud. I've also heard that a very slight rattle sound can be heard from under the car before the bearing fail completely and cause the motor to be destroyed.

cbzzoom

I don't see how that could work. The idea is to remove the seal on the engine side of the bearing. You can only access the clutch-side of the bearing from the outside, and you can't get the bearing out. How are you removing the interior seal with the bearing in the way?

cbzzoom

There have been a number of cases reported on the 996 board where people detected the bearing coming apart before the complete failure occurred, and their engines were successfully rebuilt.

Spiffyjiff

from LN:

Engines replaced or vehicles purchased in or after MY2006 should have the revised, larger single-row IMS bearing, identifiable by a larger 22mm nut in the center of the IMS hub flange. This uses a very large 6305 single-row bearing with a load rating similar to the dual row 6204 bearing compared to the earlier single row 6204 bearing which has about 2/3rds the load rating of the 6305.

Revised Single row 6305 bearing IMS with larger diameter stud and 22mm nut configuration, shown with the hub flange removed. Although the bearing is accessible via a removable circlip, you cannot remove it from the IMS without disassembling the whole engine because the o.d. of the bearing is larger in diameter than the opening in the back of the case