bazhart

Sorted the weird additions to my text above now and look forward to hearing from interested intelligent technically minded people with actual experience (like Jake and LN) about our findings and theirs.

Baz

bazhart

Black 997er - sorry - but one thing I have learned when trying to help owners is not to give opinions on oils because it opens up a can of worms in which everyone and his dog know more than I do. I suggest you find someone else to advise you.

Sorry again and Best regards,


Baz

Charles Navarro

We do carry the DI40 as well:

https://lnengineering.com/joe-gibbs-...12-quarts.html

Here are the viscosity specs for DI40.

Kv100= 13.98

Kv40= 81.18

VI= 178

When we were developing it, it was designed as a 5w40. It's final version ended up technically as a 0w40, but it's barely a 0w. HTHS Vis is 4.2 compared to M1 0w40's 3.6.

Charles Navarro

I'll add a few observations from the literal thousands of blocks we've seen since we started sleeving blocks:

- Injectors going bad on cylinders that have scoring indicates that is one component originally overlooked. We're thinking that injectors are going to need to be replaced at set intervals, as rebuilding them has not proven to prevent this failure. I spoke to one shop owner at Tech Tactics had put a factory shortblock in and 2000 miles the shortblock suffered the same scoring on the same cylinder. Injector had been rebuilt and tested fine.

- Other than a 3.2 block from Russia, I can't remember the last time we have seen scoring on a 2.5, 2.7, or 3.2 with cast pistons.

- Scoring is typically limited to bank 2, but I have seen a few (just a few) with scored bores in all cylinders. Usually Cayenne v8 blocks have the same issue with bank specific scoring. I do want to note that Porsche eventually changed to have bank specific offsets and I believe that is why we see far less scoring in 9A1 engines and later Cayenne v8s.

- We see 3.6 and 3.8s with scoring ten to one over 3.4s. Obviously there are more 3.6 and 3.8 engines out there than 3.4s, but the piston offset coupled with the poor rod/stroke ratio don't help. As Porsche increased the stroke, rod lengths shortened. The 2.5 for reference has the optimal rod/stroke ratio.

- When developing the original RND program, we found the factory forged pistons needed a bit more clearance, so we opened those clearances up without any negative effects. We also found many forged pistons with collapsed skirts, where I cannot recall seeing a single cast piston with collapsed skirts. Every piston was measured and bores match honed, so we had to check all pistons.

bazhart

Thanks for that Charles, we too are in the thousands of Nikasil cylinder replacements and build on average 4 engines/week while supplying many more blocks with new cylinders Worldwide.

Most of my text above is relating to the differences in the failed 9A1 engines we have worked on and I agree with your general findings with the Lokasil blocks.

The first hard iron coated pistons didn't score bores because the surface was hard enough to resist the released silicon particles penetrating the surface (and the particle size was smaller).

Later engines had larger silicon particle sizes (which reduced ovality creep) but impinged on the now plastic coated pistons resulting in bore scoring.

The 9A1 has Alusil (as very successful previously in 944/968 engines) but a different piston coating that is not quite as hard as the originals but much better than plastic!

By not changing the block height or cylinder spacing when increasing capacity from 2.5 to 2.7, 3.2, 3.4, 3.6 and then 3.8, Porsche did compromise the rod length to stroke ratio - but they work Ok if the cylinders survive.

The piston offset is odd - right one side and wrong the other until the 3.6/8 engines, then the same both sides and then back to right and wrong in the Gen 2 9A1. We don't see this as a major issue though.

It would be good if anyone over there has a scored (really a seized) Gen 2 9A1 block and can measure the bores very accurately (with a bore comparator) near the seized one and next to it at different positions and heights and compare notes with ours - all of which had the same shrinkage.

Best regards,


Baz

sumbaco

I know that the answers to this question are likely to range from no to hell no, but I'll ask it for the one percent chance it leads to something useful. Is there any advantage to adding a small amount of synthetic two stroke oil to the gas to help lubricate the cylinder and help prevent lspi? Especially if the engine is going to be run in less than ideal conditions?

HenryPcar

At this point all we know is that there is cylinder bore scoring and no tell-tale definitive cause as to how and why it happened. There are speculations on coating peeling off from the cylinder or piston and even motor oil related failures. There could be a gazillion reasons of what is the root cause and until there are more datas to support a definitive answer to the cause of the problem, it is for now only speculation.

HenryPcar

After reviewing the video, I must say the score pattern on the cylinder is very unusual. The scuff area has 2 distinct patterns on the left and right, and yet the center of the looks in good shape. It is almost like there are scratches to 2 sides, leaving the center untouched. So the question is although the wear is on one side, attributed to the rocking action of the piston, but then why there are 2 scuff patterns with the center surface almost in pristine condition. Could it possibly be the failure of the arrest pin on the piston connect rod, thus causing the piston to vibrate and scuff 2 wear patterns ? Perhaps looking at the wear pattern, and the condition of the connecting pins there could perhaps be a means of tracking down what was the source of the problem.

anewman

Guys - Bronz has been very generous, along with Jake, about sharing the very interesting details of this very rare incident. We all wish Bronz the best outcome with his new 4.0. BUT - PLEASE lets not allow this very rare incident become blown out of proportion. The sky is not falling, and it is only up to US to prevent this from propagating into become a new, unfounded, urban legend that ultimately devalue our 997.2, like this forum did to the 996's and 997.1s. I ask everyone reading this to remember the tremendous value, reliability, and strength of the 9A1 motors, and NOT let this run amuck. Keep cool and carry on, the 997.2's and the 9A1 motors in them are outstandingly solid. Lets keep that reputation in tact.

caitov

^ Well said.
There's a reason why multitudes of knowledgeable people have said this is one of the most bullet proof engines Porsche has ever built - because it is.

rtl5009

Quit acting like the 997.2 isn't going to have problems. Its simply coming into the stage of the life cycle that the 997.1 has already been through. I am sorry to burst your bubble, but it is the truth!

Chris M.

Do you see more scored 3.8s vs 3.6s?

edomund

rtl5009 did you read through this thread? What you are saying is the opposite of the data found in this thread.

Two of the most knowledgeable people on this board have both said in this thread that the 997.2 9A1 is a REALIABLE ENGINE and that failures are rare. Read their quotes below from this thread.

Flat6 Innovations, "l will add that any of these failures are very rare, and to date the 9a1 has been light years ahead of where the M96 engine was in it’s first decade of practical use. By this point with the M96 l had already noted 20 modes of failure, and our line for engine build was out the door, and around the building. Today the 9a1 still only comprises 1/3 of our work load here. These engines have proven to be very robust".

Baz from Hartech, "They are fantastic engines and this fault will either be a very rare and unpredictable one that afflicts a very small number of all of them - or the issue may have been addresses so only early ones suffer. Unfortunately because early ones will probably have also experienced the most heat cycles statistically they would be the most likely to exhibit the fault first either way - so only time will tell which scenario will apply.
I would expect the numbers to be far too small to worry anyone and I don't think there are any steps to reduce the problem except that if some cylinder bores are shrinking in at the bottom, the best way to extend the life of the engine is too thoroughly warm it up before giving it too much throttle - because the piston will seize if it grows bigger than the bore and this is most prevalent on warm up cycles where too much throttle has been applied too soon".

edomund

I'd also like to add my thoughts. I raced motorcycles for years and currently race jetskis and have assembled all of my race and recreational engines. I have assembled hundreds of engines and seen plenty of engine failures. Based on my observations through the years I agree with Baz and Jake. I think there are 2 things happening.

1. I think there is a VERY SMALL number of engines that the cylinder has shrank or is out of round due to the reasons Baz notes in his posts and when an engine is not totally warmed up the piston is too large and can score or seize in the cylinder (I’ve seen this many times). Baz noted most failures he has seen were in the winter. I want to add that this is not necessarily the fault of the owner. If it's very cold outside the temps on the gauges can show it’s warmed up, but the cylinder and piston are not the same temp as Baz noted.

2. These engines use forged pistons for their inherent strength. The downside of forged pistons is that they can expand more than cast pistons. If an engine using forged pistons is not totally warmed up you run the risk of scoring or seizing. I have seen this many times with other people’s race skis when they don’t warm it up properly and hammer the throttle or let someone else ride their ski and it hasn’t been warmed up. For this reason I always run cast pistons in my recreational engines because you can for the most part jump on it and ride. For our race engines (that use forged pistons for various reasons) when we are at a race we always go out for a warm up lap RIGHT before our moto to ensure that the engine is warm and when the race starts we can hammer the throttle right away.

These are great engines, but they are high performance engines and thus need an extra bit of care and procedure than a typical engine when using them.

bazhart

The problem we found on all 5 we measured was the same and I suppose another explanation could be warm up rates influencing the rate of stress relieving.

The main bearing shell area of the casting is very thick and so if engines are driven hard too soon that part of the crankcase heating and expanding will lag behind the cylinder area and this in turn creates a local stress so when they both cool back to cold there has been a typical stress relieving episode going on in that part of the block. However it isn't just the differential heating and cooling because we measure them cold and the shrinkage is there to measure afterwards.

So it could just be that cars that were used for several years with rapid warm up cycles exhibit this shrinkage when those warmed up more slowly (or perhaps never driven as hard anyway) do not.

Either way in my experience an engine is not fully warmed up until it has been driven at least moderately for 20 to 30 minutes so anyone only or mainly doing short journeys would also affect the stress relieving process and perhaps some do shrink and others do not depending on the use they have been put to.

I would guess that regardless of whether they are mainly used for long or short journeys - being patient and allowing a more gradual warm up before driving aggressively would delay shrinkage or possibly stop it ever occurring.

Baz