All "IMS failures" are not IMS failures! Carnage within! - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Jake Raby · 10-20-2009, 01:59 PM

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 · 10-20-2009, 04:53 PM

Thank you for keeping us educated Jake.

pcs5978 · 10-20-2009, 05:51 PM

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 · 10-20-2009, 06:40 PM

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 · 10-20-2009, 07:16 PM

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 · 10-20-2009, 07:29 PM

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

Jake Raby · 10-20-2009, 07:34 PM

Quote:

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!