Tampa991

Back to the original topic...I hope this issue does not occur to many of us.

Noah Fect

Oil analysis carried out by labs like Blackstone is done to look for contamination and foreign elements. They couldn't care less about the oil itself, it's not their job. What Blackstone does is as different from what tribologists do as what your mechanic does is different from what an automotive engineer does.

This entire thread is bad, and everyone participating in it except me should feel bad.

VII7

LOL

NuttyProfessor

hahaha funny line!

Seriously, please expound on the difference between Tribologists and Blackstone?

limegreen

speak for yourself, I learned a lot in this thread. Mainly that Porsche doesn't know anything about engine oil.

Airbag997

I agree.

NuttyProfessor

That doesn't surprise me.


I'm a sucker for a good analogy. Please show us your power Noah... flood us with information... split the waters of knowledge man!!

Basically, your analogy is this...
"Blackstone is to a Tribologist like a Mechanic is to an Automotive Engineer"

Expound for us. Are you saying that Blackstone Lab techs are basically kids with home science kits?

JimmyChooToo

I have a 996.1 3.4L and it loves Liqui-Moly Molygen. Noticeably smoother idle and revs like a sewing machine at high rpms. I have a Ferrari California and it absolutely hates Liqui-Moly. Liqui Moly Leichtlauf made it idle like it had a broken engine mount and it would shake the entire car until I took it out. Any changes in idle is extremely noticeable in a flat-plane crank, front-engined V8 (probably why they never used it until the F149). I used Ceratec in my SAAB turbo. Awesome product. Silkened up a high-mileage engine.

limegreen

Getting back on track, I went back and re read the " bore score and seven years ago" article from the Feb 2019 issue of Panorama.

Other than outlining the entire situation and awesome rebuild work utilizing LN's incredible fix, there is no mention of what might have caused the issue to occur in the first place. The authors car ( Carl Spencer) had extremely low mileage at the time on what appeared to be a well kept 997.

SO the question is : What is the leading theory among experts right now as to the cause of this bore scoring issue? Why has it become the most prevalent issue now seen by Charles Navaro at LN?

More importantly and most concerning is how does what happened in the M96/97 engines cross over to the 9A1 used in the 997.2 and our 991.1's? Other than the engine configuration and basic layout, the engines are completely different right down to the cylinder liners.

NuttyProfessor

Check out Jake Raby's most recent videos on Bore Scoring on the Rennvision YouTube Channel. It's also shown on Amazon Prime. I suggest watching at least part 1 and part 2 in order to answer your question(s).

digits

Rennlist always delivers - this thread turned out to be quite an unexpected treat!

Any other theories on what is most likely to have contributed to scoring in just one of the six cylinders?

Airbag997

Injector failure leading to pre-ignition (Some people call it LSPI, I disagree, just plain old pre-ignition, not enough BMEP to hit LSPI in a non forced induction motor)

Tampa991

I contacted Jake Raby’s team about 991 bore scoring, see the below response:

Thank you for your email about cylinder scoring.

Although most emails about cylinder scoring are from concerned M96/M97 owners with Porsche Boxster, Cayman, and 911 models from 1997-2008, this issue is not one limited just to these models. It can also affect other models with Lokasil or Alusil bores including Panamera and Cayenne models as well as other European makes with similar block technologies. 2009 and later sports car models with the MA1 (9A1) engine can also suffer from cylinder scoring, but it is nowhere near as prevalent as with other models.

In a Lokasil or Alusil bore engine, when the Ferrostan coating on the piston skirt wears through or flakes off, the result is aluminum to aluminum contact in the cylinder bore which causes adhesive wear, also referred to cylinder scoring.

Based on over a decade of observations, bore scoring is typically limited to models with forged pistons, so the Boxster 2.5, 2.7, and 3.2 models as well as the Base 2.7 Cayman engine typically do not suffer cylinder scoring.

Engines with failing or bad injectors or anything that might contribute to the engine running too rich can also cause cylinder washdown, leading to cylinder damage, but this can occur with any engine or cylinder technology, however the Nikasil process used in earlier aircooled Porsche engines is one of the most durable cylinder finishes and not prone to scoring.

Watch for one tail pipe being sootier than the other or for ticking noises coming from the engine when at full operating temperature. Misfires with fouled spark plugs coupled with increases in oil consumption aren't always the first signs of cylinder scoring.

Here are a few things you can do to help lessen your chances of scoring:


1. Change your oil every 6 months or 5,000 miles with Driven DT40 on 1997-2008 models with the m96 or m97 engine and DI40 on 2009 and later models with the MA1 (9A1) engine. If you do frequent, short drives or operate the car in a cold climate, you should change your oil every 3k miles or 3 months.


2. Use Top Tier fuels and Driven Injector Defender at least every 3,000 miles or better every fill up.


3. Install a low temperature thermostat.


4. Especially in colder climates, once the engine gets off cold start, don’t idle the engine any more and start driving. Limit yourself to 50% throttle and keep the engine under 3,500 rpm until the engine is at full temperature.


5. Add used oil analysis to your toolbox. Scored cylinders typically will be visible in test results with elevated aluminum and silicon levels, often with reduced oil viscosity and increased fuel contamination.

6. Interrogate the DME to observe fuel trim values and check for pending or active faults regularly. Beyond malfunctioning mass airflow (MAF) or oxygen (O2) sensors, changes to fuel trim leading to rich operation are indicative of a problem that can also stem from vacuum leaks from cracked AOS vent tubes or oil fill tubes.

limegreen

Lots of great information, Thank you for sharing!

It appears to me after watching the Flat 6 videos that the primary source of this issue regarding the m96/97 engines lies in the inherent design and manufacturing processes that are exposing a weak point in much the same way as the IMS issue where by under less than perfect conditions excessive wear/damage can occur.

For instance, I did not know that those m96/97 engines had a slightly less than favorable rod ratio resulting in additional side loading of the piston skirt against the cylinder wall but that seems to be one of the bigger contributing factors in this along with the less than optimal durability of the lokasil/alusil coating. I understand there are many other factors in this "equation" but I'm trying to find the similarities between the m96/97 engines and the 9A1.

Does anyone know what the rod ratio is in the first gen 3.6, 3.8 (997.2) and the second gen 3.4 , 3.6 ( 991.1) 9A1 engines?

verstraete

Add Item 7.

7. Never drive a Porsche that is not under warranty

Seriously, I have a Ph.D in aerospace/mechanical engineering, am a veteran of the aerospace industry, and have taught mechanical design courses to engineering students for many years. A street vehicle that requires steps 1 through 6 to avoid catastrophic engine failure in normal daily use represents a badly flawed design. The only way I can rationalize my continuing use of a 991 as a DD is by maintaining warranty coverage while exerting only a reasonable level of care and maintenance. Using Top Tier Fuel and avoiding flogging a cold engine, for example, seem like good general practice with any vehicle.