All "IMS failures" are not IMS failures! Carnage within!

[dmcutter]

Jake, I don't think they use gavels all that much in suits, but maybe Lovebunny can weigh in on that one.

[Jake Raby]

This engine came from a Boxster with a manual tranny.... Owned by a Female that bought it new.

[blue2000s]

I don't like the idea that the guide is a wear item. They should be rollers instead. I built the attached in CAD. More rollers are better but this conveys the idea. If you want, I can help you develop the part with CAD and finite element analysis. Send me a PM.

[MikenOH]

Did one of the 3.2L tensioners survive the damage intact? If so, could you post a picture of the 2 side by side.

Is it fair to say the "newer" design is less robust than the old 2.5L design? If so, what would you guess the cost of material saved might be between the 2 parts?

Thanks

[catmanluge]

Now we have another weakness to worry about! This may just be a rare failure I hope!

[Jake Raby]

Originally Posted by blue2000s

I don't like the idea that the guide is a wear item. They should be rollers instead. I built the attached in CAD. More rollers are better but this conveys the idea. If you want, I can help you develop the part with CAD and finite element analysis. Send me a PM.

This design also has some issues as the roller axles are a failure point and the contact patch of the rollers would result in point loading. The drive chain is also a very hard composition that would create some challenges in metallurgy development and heat treat of the rollers, it would be easy to create more issues with chain wear with an arrangement like this. I do appreciate the concept and your input.

We do solid modeling and FE analysis in house along with LN Engineering on all the update components, but I do appreciate your willingness to assist us with the design of the updated component.

[blue2000s]

Originally Posted by Jake Raby

This design also has some issues as the roller axles are a failure point and the contact patch of the rollers would result in point loading. The drive chain is also a very hard composition that would create some challenges in metallurgy development and heat treat of the rollers, it would be easy to create more issues with chain wear with an arrangement like this. I do appreciate the concept and your input.

We do solid modeling and FE analysis in house along with LN Engineering on all the update components, but I do appreciate your willingness to assist us with the design of the updated component.

Very simple, add shallow teeth to the rollers and they turn with the chain. Like I said, it's just for the concept. Point loading is what a bearing is made for. This is a very simple problem to fix.

[Jake Raby]

We have to be very careful not to create a new problem while trying to solve another... This is something we fight all the time as we work to create solutions and what seems simple, generally never is.

Lots of the things inside this engine has simple fixes, but unfortunately this is not an area that is easy to access or inspect as it takes 6 hours of labor to access this component.

If we decide to experiment with bearings I'll certainly contact you...

[Jake Raby]

The second occurrence of this mode of failure in 10 months.. Yet again this one was misdiagnosed as an IMS bearing failure.

The IMS bearing is intact and has no symptoms of failure, but upon inspection we found a chunk of the IMS tensioner paddle wear pad in the oil sump. This sparked a boroscope interrogation of the IMS area through the IMS tensioner bore after the tensioner was removed.

The engine is not totally apart, but after I did a thorough inspection with the boroscope I can see that the tensioner paddle is missing it's plastic wear button and the entire wear pad has been ripped off and chewed up by the IMS drive chain. The remnants are laying at the bottom of the crankcase beneth the IMS drive as depicted here in these somewhat blurry photos from my boroscope from deep inside the engine.

The early engines had metal wear buttons for the IMS tensioer to rest against, that was too expensive so around 2001 this was changed to PLASTIC and when it wears thin and fails this sort of failure occurs since a ton of 'slack" exists in the IMS drive chain which causes the chain wear pad to be eaten up, resulting in an engine that has variable valve timing in a very bad way. The billet chain tensioner paddle that we have made with LN Engineering includes a STEEL wear pin that will resist this sort of failure; needless to say I use this in EVERY engine we build.

This engine is more than likely totally nuked. My forecast is that the majority of the pistons have had collisions with the majority of the valves and that most everything internally looks like 3 mile island.

More will be known when I complete the autopsy and fill out the failure report. For now it's clear to see that the IMS and chain are intact but that the wear surfaces and plastic wear button are FUBAR.

More pics later

[Jake Raby]

BTW- Here are some shots of the billet chain tensioner paddle vs the new, revised Porsche component.. Theirs is still plastic and cast aluminum.

Go overkill.

Here ya go.. These pics are of the newest Porsche revised part Vs the LN/ Flat 6 overkill component. Ours is the shiny, heavy duty one, theirs is the cheap cast aluminum one.

Shiny doesn't mean better, if you feel the difference in the weight of the parts alone you'd know the difference.. And you can't buy a new one with a STEEL wear pad for the IMS chain tensioner!

[kabel]

Thank you for keeping us educated Jake.

[pcs5978]

I'm pretty certain Jake has done more M96 autopsies than anyone - anyone that is other than the guy(s) who work for Porsche AG tearing down blown up M96 motors - and those guys aren't talking.

This is the second failure he's seen like this and it occurred in an '03 M96/24, three chain motor with approx. 60K miles. There's not much that this 986 owner could have done to prevent this. Tic, Tic, Tic Boom!

Jake's contribution to this thread included photos of "The Replacement" tensoner paddle that he's developed along with Charles Navarro at LN Engineering. He gives you a description of the differences between the two. I have the first motor that this "Replacement" part was installed in. What Jake doesn't say in the thread is what was actually involved in fabricating the part. Once this problem was identified (N=1, now 2), there was an active decision not to rebuild my motor until this part could be perfected, because if this part breaks, there is nothing left of your M96 to rebuild.

It took three prototypes and nearly 4 months of work to get it right. Only then was my 3.6 upgrade reassembled - The guys are persistent! When I looked at the LNE website, the part cost $249 - this is an ounce of prevention.

Engine development is an iterative process. You build it, you drive (track) it, you break it, you analyze it, you fix it. Then you do it all over again. This mode of M96 failure isn't a common problem, but it is a problem. Any M96 rebuild need this "Replacement" part.

[jaykay]

Well I hope having a 2000 3.2 with a steel rest pad rather than plastic will keep me a bit safer than most!

Nice idea with the rollers! One has to consider the chain shape produced with them especially the speeds we are talking about; I would guess flat would be better. Any bearing dia that small is going to be doing some wicked rpms assuming no skidding/wear; one will need to ensure strength/lubrication at these sites...increasing the bearing dia will weaken the the arm at points; all in a limited space.

From what I can see the LN arm has a greatly increased web area which would give increased strength. I am surprised the Porsche arm fails as it has. It must be a combination of poor castings or choosing to put a casting where one shouldn't and shock loading resulting from the rest pin failling......just a guess without seeing the set up of the engine

[Jake Raby]

When the factory changed the IMS drive chains in the '01 model engines they also changed the metal tensioner contact pins to the plastic type...

Phil's engine had a metal wear pin because it was a 2000 model Boxster S, the only "S" with the metal contact pin and the old style IMS drive arrangement.

I probably won't have time to tear this core down for a while, but when I do the failure report with pics will be posted.

[jaykay]

Thanks much appreciated.........Jake you must have been an aircraft mechanic or turbine engine specialist. Nobody else usually utters the word boroscope....

[Jake Raby]

Originally Posted by jaykay

Thanks much appreciated.........Jake you must have been an aircraft mechanic or turbine engine specialist. Nobody else usually utters the word boroscope....

Yep, worked with T58 and T64 GE Turboshaft engines as a Marine when I wasn't crewing CH 46E Helos..

Phil calls it a bronchoscope :-)
He has been trying to find me an even more bad ass unit than what I have now.. This new one does video and allows for narration as well, its really sweet!

[catmanluge]

Jake

Is it possible that the plastic button let go first and then the ware of the guide increased?

[Jake Raby]

Originally Posted by catmanluge

Jake

Is it possible that the plastic button let go first and then the ware of the guide increased?

That is exactly what happened.

I am working on an extraction procedure for the plastic wear component that can be replaced in the car, engine assembled. LN and I already have the metal wear surface made that can replace it as a retrofit.

[clickman]

Originally Posted by Jake Raby

I am working on an extraction procedure for the plastic wear component that can be replaced in the car, engine assembled. LN and I already have the metal wear surface made that can replace it as a retrofit.

I can't wait to see this piece of magic