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All IMS failures aren't really "IMS Failures"


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Victim: 2001 M96 engine pulled from a Boxster S. Mileage reported to be 45K

Catastrophic Failure

MOF #14

We have discovered another MOF (Mode Of Failure) related to the M96 engine. This one is our most recent tear down that occurred with a 45K mile engine. It is one of the most radical failures that could occur with an engine and we have gained a good understanding of why it occurred. More importantly we are in work already on another "overkill" part to solve this issue that we can apply during our engine updates for our complete engines and component kits.

This is interesting, because this engine fooled us, it also fooled a Porsche Dealership and another independent Porsche shop that had diagnosed the engine prior to it being sent into us. The engine had all the classic symptoms of a seriously failed IMS that had resulted in valve timing alterations, thus colliding the majority of the valves with the pistons, a true nasty affair. When the intake manifold was pulled we immediately saw carnage (broken valves and chunks of piston in the intake ports!) and since I love to dissect engine failures I stayed late to see what was inside this beast.

As the engine was torn down I was expecting to see the IMS shredded, but every time we turned the engine while removing the valve train the only symptom that the engine had was altered valve timing, this was odd. Typically when an IMS fails this badly the shaft shears in half and "parks" the valve train that operates from the opposite end of the IMS drive, located at the flywheel end of the engine (I am trying to explain this so you guys can understand!) and that results in all the things we had witnessed. When this happens the IMS will not turn, so the oil pump stops functioning and 3 cylinders worth of valves stop actuating, resulting in a big mess.

This is where it gets interesting:

When the IMS fails to the point of allowing piston collisions with the valves the IMS is most always sheared.. But when this engine was rotated fore and aft the IMS was responsive to the change in crank position and the typical damage to the oil pump that results from IMS failure was not present.

How could an engine have such a radical failure, with all the same initial symptoms as the IMS failure and have an IMS that was responsive to crank position changes, intact and still functional??? Read on...

When the first cylinder head was removed the engine still had all the symptoms of an IMS failure, but when the second head was removed that cylinder head was found to be perfectly intact with zero piston/valve interference and no damage. The engine was still spotlessly clean inside and showed no signs of abnormal wear on the "intact" bank of cylinders.

As we went deeper it got interesting as it seemed the valve timing was radically off on both sides of the engine, but all the timing chains were intact, nothing was broken and all was in decent condition. At this point of the autopsy we knew that when the case was split we'd find something we hadn't seen before.

When the case was split the IMS came out in good condition without any oil inside it and without any signs of bearing failure or wear. We immediately removed the crank carrier and then we saw the culprit..... The crank/ IMS drive chain tensioner pad was non existant and the tensioner was broken in half! We then dug through the rubble and found the broken pieces and started putting the pieces together to figure out what happened.

Why the valve timing changed:

Because the main drive chain for the IMS lost all tension when the "tensioner" sheared in half, thus allowing the IMS to stop rotating and "parking" the valves. When this occurred a couple of cylinders had open and partially open valves that then collided with their pistons and that resulted in scattered parts, a loud bang and chunks of piston being emitted from the tail pipe...

What we learned:

Something we had never really paid close attention to was the shape and thickness of this tensioner through the various years and models of the M96 engine. We pulled this piece from several engines and started comparing them in shape, interchange, composition and design. We immediately noted that the the early 2.5 tensioner was thicker across the area where this tensioner had broken and that the early unit also had a hardened steel contact surface for the chain adjuster to ride against. The later 3.2 unit had been made thinner through the area where the breakage occurred and had a PLASTIC surface for the chain adjuster to contact.

The part number from the two parts were the same, but one was a .4 while the other had a .5 suffix.

So, why was this part changed? Why would anyone ever replace a hardened steel wear surface with something comprised of plastic, when even the steel wear surface does typically wear....

This is a MOF that we have never seen before and never heard of occurring. After seeing this failure and it's symptoms I believe that some of the "IMS failures" that are diagnosed without an engine tear down are actually this MOF, or at least something similar to it, that cannot be thoroughly understood without complete dissection of the engine.

That said, we are already in work creating a two new components that will solve this MOF issue. First we are making a billet aluminum tensioner unit made to use the OE tensioner pad, this will replace the lightweight, cast aluminum factory unit. This will incorporate a larger, tool steel wear surface much like the earlier 2.5 unit pictured below. Making the wear surface larger will increase the contact patch that the chain adjuster sees, thus increasing service life.

Secondly we are making the wear surface "button" compliant with the OE tensioner, so those that have the early tensioner can replace their wear surface with a larger, stronger part if they don't choose to utilize the entire billet tensioner that we are creating.

I'll never trust one of these OE tensioners again, we'll be applying the billet units to ALL our engines effective immediately and all builds are currently halted while this component is being made.

The key to avoiding problems like these are to make the parts heavier duty than they "need" to be on paper... I call it "overkill Engineering" and it's what keeps things from failing... Its nothing more than classic hotrodding being applied to these newer, robotically assembled, mass produced engines.

We are now going through cores and doing research trying to specify when Porsche changed this tensioner.... I'll report back when we have concrete evidence.

Now for the pictures... More will be posted today on the "reliability" page at www.flat6innovations.com

The pictures speak for themselves, its mass carnage of an unreal kind.. The kind of stuff that makes it to our "trophy Shelf" filled with offerings to the Gods of Speed...

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post-34760-1231775098_thumb.jpg

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you da man Jake! Whats up with porsche and their little black plastic parts?!?!?! Cheapskates. They already have the highest profit margin on ANY car in the world..you would figure they could spare a few bucks a car for proper metal parts:(

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The metal wasn't breaking so they figured it was "over engineered"...

:o The ghost of Colin Chapman!

And the ghost of a previous 911 problem with tensioners.

So should we all be lining up for preventative replacements?

What does it cost?

Thanks, Jake.

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To uncover this tensioner the ENTIRE engine must be torn down, if you notice the tensioner attaches to the crank carrier, the first assembly installed into the engine when building it and the last assembly removed at tear down. There is no way to apply our updated part without removing every bolt from the engine, unfortunately.

And when you buy a replacement Porsche engine, guess what part they use :-)

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Could it be possible that a valve head broke off causing the loading on the chain to be increased and breaking the tensioner arm? I know everybody to quick to blame Porsche and all the cheap parts they use but as nobody has seen this part fail before I'm wondering if it a design flaw or perhaps just a bad part.

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Despite what this engine had impact it first, this failure illustrated a weakness within the engine that could come back to bit me in the *** later down the road.. Anytime we witness something like this we must act upon it.

Even if a valve snapped first, the tensioner should have been strong enough to absorb the impact...

Its hard to tell exactly what happened first because the carnage is so bad, its lind of like crime scene investigation with a dead body thats been decapitated... Near impossible.

I learned a bit more that I have not posted just yet, still waiting on some more evidence..

I do not believe that the issue occurred upstream in the valve train as trhere was no damage to any of the vario cam assembly, or etc that would occur IF a shock of this magnatude occured and sent a shockwave through the IMS and to the tensioner.

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Scary stuff...one more thing to wonder about? I'm still at a loss to understand why Porsche took so many shortcuts, especially with their history of over-engineering most their applications. What did this save per car; a couple hundred dollars, at most?

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The cars that built the Porsche brand were assembled by hand, not by robots.. Their engines were also built by hand, some by one individual.

In those days the German Engineers called the shots.. Today the German Accountants are in command.

200 bucks per car multipled by the production rate of the Boxster and 996 is millions of dollars, where if it were still the 356 days it would not have been very much at all.

We are building engines and creating parts the way that Porsche did yesterday.. One individual applies the upgrades and developments and takes the engine from an assembly of parts through it's dyno testing procedures. Its the way Porsches were designed to be built and the only way that I'll stamp my name on anything.

All it has taken to create solutions to these inadequacies is an outlay of money and expenditure of effort.

Edited by Jake Raby
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Whats up with porsche and their little black plastic parts?!?!?! Cheapskates. They already have the highest profit margin on ANY car in the world..you would figure they could spare a few bucks a car for proper metal parts:(

Some type of phenolic is pretty much the industry standard for internal chain tensioners. Do you have any idea how loud the engine would be if the tension surface was metal?

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Whats up with porsche and their little black plastic parts?!?!?! Cheapskates. They already have the highest profit margin on ANY car in the world..you would figure they could spare a few bucks a car for proper metal parts:(

Some type of phenolic is pretty much the industry standard for internal chain tensioners. Do you have any idea how loud the engine would be if the tension surface was metal?

It would be loud and wear would be hard to control on the chains... Something has to wear..

We are working on procedures and modifications to increase oil delivery to this area of the engine in an attempt to provide a solution to the tensioner pad wear issues.. The best part is that my initial concept may be patentable.

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So does this mean that the latest direct-injection engines on the 997-2 and the incoming facelift 987 Boxster/Cayman could still have "catastrophic engine failure" even when the new engines do not have the intermediate shaft?

Too bad there's no way to check or access the tensioner. So basically we can just hope and pray that the engines don't blow up in the meantime, and when time comes to get it overhauled, then strip it all the way to the tensioner.

It makes me wonder then -- this IMS problem seems to be this mysterious disease that doesn't seem to have a logical or easily pinpointed cause (be it driving style, maintenance, mileage), highly unusual. Is it possible that Porsche, who should have a fair few engines shipped back to them from around the world during warranty repairs, knows about your discovery and has just kept mum about it and perhaps snuck in updated fixes into the new engines?

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The new engines do not have this particular component, as it drives the IMS, a component they do not incorporate. Porsche sees these engines by the hundreds and I am sure they know how they fail, they don't need us to illustrate it to them.

The new engine will have its own flaws, I am already trying to buy one so we can dissect it and start designing "fixes" for it as they pop up... Any new design breeds a fair amount of new problems while trying to address old ones.. It happens with anything thats manufactured and has even happened to us.

I have several ideas about what causes the IMS issues but we need to see atleast a couple dozen more failures and fullyn investigate and compae them before I divulge the information.

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  • 2 years later...

Jake is right, I have this problem now the tensioner let go. When I heard this noise I turned the car off & restarted to I hear the sound again but better for a second or two. The engine started

right up the second time but with noise, the infamous marbles in the can but louder sound (slightly masked by the supercharger) the oil ran out the engine I thought the ims was the culprit but

there is some small parts on the tensioner plastic in the oil filter housing. and no oil where the ims and rms usually leak. Note the code was for the camshaft solenoid and not misfiring on any

cylinders which leads me to believe the tensioner let go and not the chain by reason of the ims bearing which would had compromised the timing therefore not starting the second time.

However nothing is sure until a complete tear down and rebuild from the crank which is in the near future. Just my .02 in to try & support the view of a very knowledgeable professional and I

know he in no way needs it...

Edited by 2fas4u
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