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Interesting. Thanks. All I see is 928 engines and bore scoring is pretty rare - and even-more-rarely catastrophic - even with serious wall washing. One might suspect that the Lokasil process just doesn't work nearly as well as the last-century cast Alusil cylinder blocks.
There were significant changes to the Alusil process from when the 928, 944, and 968 engines were originally produced. Specifically the silicon exposure process was changed which can result in more torn of fractured silicon particles which then in turn reduce the load bearing capability of the cylinder walls. Secondly, the iron clad coating on the pistons was replaced with a printed wear pad which has shown itself not to be anywhere as durable as the older plating process which manufacturers went away from because of environmental reasons.
Lokasil suffers from the same issues for similar reasons, but there is a lot more going on there. The fact that Porsche was the only manufacturer to ever use Lokasil and they stopped using it after the M96 engine says it all.
Just curious, Charles, if you have any comments on the performance of the Rotating Single-Wire (RSW) bore lining process used on the 9A2 (991.2) - as compared to the previous processes.
Just curious, Charles, if you have any comments on the performance of the Rotating Single-Wire (RSW) bore lining process used on the 9A2 (991.2) - as compared to the previous processes.
cheers!
Night and day. The RSW or APS coated bores are much more durable. I have experience with Oerlikon's SUMEbore coatings (used in the 918 Spyder among other Porsche and VAG products) and it has worked phenomenally. Performance is on par with Nikasil and likewise has excellent heat transfer like Nikasil since it's only applied .0045" thick. I would not be concerned with cylinder bore scoring on the newest blocks using this technology.
Here is a picture of an M96 block we did with SUMEbore after being run and torn down for inspection. Engine was reassembled and is back on the road now. Lake Speed Jr. from Total Seal (previously Driven Racing Oils and Joe Gibbs Racing) owns the car we're doing the over the road testing with. We have done an aircooled Porsche test engine as well and the results were excellent. Our next step is to evaluate some of the other Oerlikon coatings as there are several variants of SUMEbore we'd like to learn more about. Very long term project we are doing in conjunction with Oerlikon, Total Seal, and Flat 6 Innovations.
Night and day. The RSW or APS coated bores are much more durable. I have experience with Oerlikon's SUMEbore coatings (used in the 918 Spyder among other Porsche and VAG products) and it has worked phenomenally. Performance is on par with Nikasil and likewise has excellent heat transfer like Nikasil since it's only applied .0045" thick. I would not be concerned with cylinder bore scoring on the newest blocks using this technology.
Did you apply the thermal coating in Momence or did you have to send the cylinders to Zürich? What is the cost vis-à-vis Nikasil?
Edit: For clarification I am speaking generally about a racing engine where the cylinders can be serviced. I'm guessing this is not the case since for an M96 engine, like you posted, as you would need to ship the entire block abroad.
Last edited by silver_tt; 06-27-2021 at 11:59 AM.
Reason: clarification
Did you apply the thermal coating in Momence or did you have to send the cylinders to Zürich? What is the cost vis-à-vis Nikasil?
Edit: For clarification I am speaking generally about a racing engine where the cylinders can be serviced. I'm guessing this is not the case since for an M96 engine, like you posted, as you would need to ship the entire block abroad.
We don't have the equipment to do it in house ($$$) - we had to send the block out to have it coated. One of my mentors is close friends with the guys at Sunnen and they were kind enough to lend us the tooling to hone the block to the mirror finish required. As you can see, there is zero crosshatch in the bores. There are micropores that hold the oil instead. Neat stuff.
Cost is still prohibitive. It's over four times the cost and that doesn't include the honing.
Yes that plasma vaporization composite technology is so cool. I see how the hone works -- the coating process actually shoot little iron pellets into the cylinder wall creating an uneven finish which, when you come back and hone it out, creates little divots that will hold the oil. Such a fascinating technology......
So, costs aside, compared to Nikasil is this a superior product? It seems like the answer is "probably yes.....but time must be the judge". Obviously it's better ring seal, less oil consumption, etc. Are there any downsides? Are any of the racing teams using this technology? Similar to Nikasil I'm assuming a bad injector can still take out a cylinder?
By the way @Charles Navarro do you guys now do rebuilds of the 991.1 engines? I know we're still within the 10 year window where factory short blocks are easily available but in a few years a rebuild may be the most economical way going forward. It would be awesome to get one of these improved coatings on the rebuild and potentially also increase displacement a bit.
By the way @Charles Navarro do you guys now do rebuilds of the 991.1 engines? I know we're still within the 10 year window where factory short blocks are easily available but in a few years a rebuild may be the most economical way going forward. It would be awesome to get one of these improved coatings on the rebuild and potentially also increase displacement a bit.
We do recondition the blocks and have for many years, however we do not rebuild 9A1 and later engines. Here's a summary of our program:
Yes that plasma vaporization composite technology is so cool. I see how the hone works -- the coating process actually shoot little iron pellets into the cylinder wall creating an uneven finish which, when you come back and hone it out, creates little divots that will hold the oil. Such a fascinating technology......
So, costs aside, compared to Nikasil is this a superior product? It seems like the answer is "probably yes.....but time must be the judge". Obviously it's better ring seal, less oil consumption, etc. Are there any downsides? Are any of the racing teams using this technology? Similar to Nikasil I'm assuming a bad injector can still take out a cylinder?
Thank you as always for the information.
With Oerlikon's SUMEbore, there are several types of coating. The one we have the most experience with is their F2071 which is designed for corrosive fuels and environments and actually has ceramic in it. It took some time to figure out the right rings to run and now we're playing with different lubricants. I can tell you it doesn't like Mobil 1 0w40... The F2071 coating is used in Europe for diesel engine blocks where durability and longevity is paramount. There are other coatings that have moly or other materials in the mix that greatly reduce friction and might possibly outperform Nikasil which we are going to be testing with this next round, but I would say the performance is on par with Nikasil, especially from the benefit of heat transfer for aluminum blocks. The big benefit of the SUMEbore process is the environmental benefits over the Nikasil or any other plating process which is considered dirty and all the OEMs are trying to go to environmentally friendly solutions.
SUMEbore has been and is used in Nascar engines and other kinds of racing. Many OEMS have licensed the SUMEbore process.
This isn't the most recent list, but is all that I have come across during my time working on this R&D project.
So, what caused the scoring? Piston slap? Leaky injector/preignition-related overheating?
Maybe it is the bore to stroke ratio. When your stroke is relatively fixed since these are boxer engines and the bore gets increased to increase the engine capacity, you end up with more of a side load on the piston and cylinder wall under heavy acceleration than you would with a longer stroke.
Here is a pic. Note the size of the horizontal force arrow.
Maybe it is the bore to stroke ratio. When your stroke is relatively fixed since these are boxer engines and the bore gets increased to increase the engine capacity, you end up with more of a side load on the piston and cylinder wall under heavy acceleration than you would with a longer stroke.
Here is a pic. Note the size of the horizontal force arrow.
Bore-stroke ratio certainly plays a factor but I don't believe it's as much as a problem on the 9A1 engine as it was on the M96 engines when they increased the stroke to 82mm from the 78mm. The increase in stroke resulted in the piston coming out of the bore 7mm at BDC (versus 2mm on the shorter stroke engines). At BDC changeover, that's putting extra load on the piston skirts and probably contributes to the premature failure of the piston coating. However, there are many factors that contribute to cylinder bore scoring which I spent over a year researching. I wrote a white paper on the topic for those interested:
With Oerlikon's SUMEbore, there are several types of coating. The one we have the most experience with is their F2071 which is designed for corrosive fuels and environments and actually has ceramic in it. It took some time to figure out the right rings to run and now we're playing with different lubricants. I can tell you it doesn't like Mobil 1 0w40... The F2071 coating is used in Europe for diesel engine blocks where durability and longevity is paramount. There are other coatings that have moly or other materials in the mix that greatly reduce friction and might possibly outperform Nikasil which we are going to be testing with this next round, but I would say the performance is on par with Nikasil, especially from the benefit of heat transfer for aluminum blocks. The big benefit of the SUMEbore process is the environmental benefits over the Nikasil or any other plating process which is considered dirty and all the OEMs are trying to go to environmentally friendly solutions.
SUMEbore has been and is used in Nascar engines and other kinds of racing. Many OEMS have licensed the SUMEbore process.
When you say F2071 is designed for corrosive fuels does that mean ethanol specifically or is that a more general statement? I see the blend material for F2071 is oxide ceramics. What if you use no blend material and use an oxide ceramic for the matrix material (F6418)? Looks like friction reduction and wear resistance are off the charts using that coating.
Maybe the most exciting thing is that the cost has apparently come down ~50% in the last 5 years. Given the direction of ICE, definitely seems like this is the way of the future. That is an impressive list of engines.
06-24-2021, 12:45 PM
