BucketList

I'm going to disagree with this assessment. The Lokasil bores are far more prone to scoring from dislodged glass beads than the Alusil bores. The 9A1 has a closed deck and improved water flow and a ferrous piston coating also. As long as I have been on this forum, there has only been ONE instance of someone with a scored bore and his engine was REALLY bad. Huge gouts in the aluminum where it rolled on itself. The guess at the time (and I have not heard another contradictory diagnosis) was that the engine seized due to piston heating much faster than the cylinder. This HAS been noted for these cars from drivers flogging it in very cold weather right from the get go. The temptation is there, cold air is much denser than hot air and you do get extra HP when everything is cold, but it's bad mojo for piston clearance.

silver_tt

If it wasn’t the case Porsche would not have gone SUMEbore in the 991.2 and later. Obviously it’s an issue….

Bruce In Philly

2009 C2S 188K miles

997.2 9A1 engine bore scoring frequency compared to .2 M96/M97 frequency: Go to 12:50

Peace
Bruce in Philly

silver_tt

It likely is the case that the 9A1 is less prone to scoring; however certainly not immune and I have seen several failures. In one of his lasts posts on RL I was having a conversation with Jake where he told me something like 90%+ of the failures they see on the 9A1 are scoring related. 9A1 also has new modes of scoring that were not seen on previous generations due to tight piston-to-cylinder clearances and the fact that is utilizes direct injection technology.

Purely from a logic perspective, the fact that Charles sees or has seen less of these failures is no surprise. The 9A1 engine is much newer and many of the failures have been under warranty and would not be seen in the aftermarket at a place like LN engineering. It makes sense that he would be seeing a lot more M9x engines and those engines have been around much longer with a lot more time/miles.

The cost of SUMEbore is very expensive and was even more so when Porsche first implemented it in the 718 and 991.2+. Prohibitively expensive in the aftermarket else LN would be using it instead of Nikasil and even in mass production it is expensive and adds significant cost to the engine production. The bean counters would not have allowed this if bore scoring was a non-issue on the 9A1.

Charles Navarro

Right now the cost for SUMEbore is somewhere around 4-6 times that of Nikasil. Oerlikon, who developed the SUMEbore process, equipment, and powders, focuses on selling the process to OEMs. They do have an R&D lab, but it isn't for production and they are not set up to service the aftermarket in any way, shape, or form.

For several years, Jake and I have been working closely with Total Seal to evaluate these coatings and develop honing processes and optimal ring combinations to make all of this work. We built an aircooled dyno mule where all the ring testing took place as well as an M96 3.2 Boxster engine that was built to 3.8 liters. The M96 engine was torn down during COVID, inspected, and re-ringed to allow for a ring change (bores did not need to be re-honed). and now Lake Speed Jr. is running around in a Boxster racking up serious miles for OTR testing. For the next step, Additionally, Oerlikon wants us to evaluate several other types of SUMEbore coatings used by VAG (and Porsche), so the testing is on-going.

Here is the M96 block with SUMEbore coated bores after it was torn down for inspection:



As you can see, there is no cross-hatch. It's interesting stuff - porosity in the coating, not valleys, holds the oil on the cylinder bore. I could go on but moral of the story is that I'm not too concerned about the SUMEbore coatings. The only question I have is if the castings themselves are better stress relieved than the MA1 blocks and I also am curious if Porsche changed the piston to cylinder clearance and/or pin offsets as I do believe these factor into the cylinder issues with the MA1 engine as much the use of Alusil itself.

I also always bring up the fact that Alusil was used successfully by Porsche in some aircooled 2.7 engines and all 3.0 SC engines and also on the 944, 928, and 968 successfully (with open deck blocks no less), but the manufacturing process, piston coatings, and lubricants have all changed greatly since then.