Originally Posted by PV997

Hi Charles - I've long believed the root cause of M96/97 bore scoring was failure of the piston skirt coating which leads to galling from aluminum (piston) on aluminum (cylinder) contact. There are lots of other contributors but ultimately I think it's the piston skirt coating flaking off that starts the ball rolling. It's also not just some scratches that's a problem but specifically aluminum galling, as that is what causes the ugly, unstoppable cascade. Seems like we are relearning some of the hard lessons of early aluminum block engine rebuilders regarding the importance of skirt coatings.

I noticed Jake had a livestream about two weeks ago where he discusses piston coat flaking (which he calls stage 0 scoring) and he alludes to this phenomena with more details to come in future videos. Looking forward to it.

What has me concerned is that the skirt coating flaking may be related simply to time (i.e. the coating becomes brittle with age) as opposed to mileage (wear). This could mean low mileage cars are just as susceptible as high mileage cars. Unfortunately, there's no easy way to inspect coating condition, all we can see are the results of it (scoring) and then it's too late once galling has started.

Following that same line of thinking, that means every M96/97 owner should assume their piston skirt coating is potentially compromised and the only thing preventing aluminum to aluminum galling is the motor oil. None of this is new thinking of course, but that would mean all M96/97 owners should follow a prevention list (along with rationale):
.

• Frequent oil changes (to guard against viscosity break down)
• Use the highest viscosity oil that's appropriate for the car's operational climate (to ensure adequate oil thickness/viscosity at the thrust face)
• Use oil with high levels of moly or a moly additive at a minimum (as moly is well known for it's aluminum anti-galling properties)
• Install a low temperature thermostat (to reduce temps at the thrust face and preserve oil viscosity)
• Never lug the engine (to reduce piston to cylinder sidewall forces at the thrust face that can squeeze out the oil and increase temps)
• Ensure injectors aren't leaking (to prevent fuel wash of the motor oil)

The last one seems more of a theoretical concern to me as the bank 2 thrust face is on the top of the engine. Visualizing this, gravity should help out here as unatomized fuel would fall to the bottom of the cylinder away from the thrust face. This would be more of an issue for bank 1 (where the thrust face is at the bottom) yet we almost never see scoring there.

Any other thoughts on this or additional suggestions?

Thinking more along these same lines, have you noticed the piston skirt coat flaking being more prevalent on bank 2? It's a chicken or the egg question. Do the higher temps of the bank 2 thrust face cause the coating to flake off? Or does the coating flake off on all cylinders but bank 2 is more susceptible to scoring due to motor oil break down?

Always appreciate your thoughts on this and your willingness to share what you've learned.

Originally Posted by Charles Navarro

That's a great summary.

With regards to fuel injectors, we have seen time and time again bad injectors associated with cylinders that have scored. I am also aware of at least one case where a new factory shortblock failed within 3000 miles from bore scoring on the same cylinder. Turned out to be a bad injector on that cylinder.

In my personal opinion, the wrist pin offset is likely the cause of bank 2 scoring first in most engines. Porsche did not use bank specific pistons for this application and I believe that having the piston offset going the wrong way does not help the situation. However I don't think it is one specific item that is the root cause of these issues but rather an accumulation of things that break the proverbial "camel's back."

Originally Posted by PV997

Thanks Charles, good info as always. I'll have to look into the wrist pin offset as I've never seriously considered it. I guess the mechanism there is increased sidewall forces due to the geometry? That would be interesting to model. Happy Easter.

Originally Posted by Brokenhearted997

There is an emerging movement among dissatisfied 997 S customers who all have come to realise that a systemic fault with the 997 S engine has left them with significant financial damage through no fault of their own. The engine block of the 997 has proven incapable of handling the bigger cylinders of the 997 S as the walls were simply too thin.

By now, more than 70% of all 997 S cars have experienced cylinder bore scoring through tilted pistons due to the thinner walls giving ever so slightly and allowing the pistons to tilt over and begin scraping. This is unrelated to mileage and has occurred in cars anywhere from 20,000 miles and upward.

This usually leads to autonomous catastrophic engine failure, through absolutely no fault of the customer.

At this point the data evidence is completely overwhelming and Porsche should really take responsibility for the serious harm and grief caused to an entire generation of customers. Lord knows they are profitable enough to show some stakeholder concern and show they care about their customers.

I hear in the United States there may be another Porsche class action lawsuit developing, led by two of the country's top class action law firms. In Germany, one of the leading Auto illustrated magazines is currently investigating, and I understand the Financial Times is doing the same.

Originally Posted by R. Moya

Hello, New to the forum. I purchased a 2006 997.1SC2 a little over a year ago from a Porsche dealer that said the car was "Porsche Certified" (We have drastic differences of that term). Any way long story short... Slight bore scoring and second gear issues that my independent shop will address. And in that discussion, we talked about my options..i.e. rebuild... FSI stage 1...sell the car. Then he tells me that he has a 996 Mezger Turbo motor that he would sell. Any Thoughts?

Originally Posted by R. Moya

Hello, New to the forum. I purchased a 2006 997.1SC2 a little over a year ago from a Porsche dealer that said the car was "Porsche Certified" (We have drastic differences of that term). Any way long story short... Slight bore scoring and second gear issues that my independent shop will address. And in that discussion, we talked about my options..i.e. rebuild... FSI stage 1...sell the car. Then he tells me that he has a 996 Mezger Turbo motor that he would sell. Any Thoughts?