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We tear down and inspect 3-5 M9X engines a week and have yet to see one where scoping from the bottom would have revealed more information than scoping from the top.
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That could easily be due to the kind of engines you receive, namely those where bore scoring has progressed that far, that a rebuild is in order (my assumption).
Or do you get a significant amount of 'elective rebuilds' where only little borescoring is evident AND in those cases the borescoring is not near BDC but somewhere halfway down the stroke?
That is a lengthy and thoughtful report as usual from Baz, but It asks the 96 thousand dollar question , then fails to answer ...
The question ;; what single thing can a finger be pointed at, that would cause bore scoring to start most likely on Bank 2 on the most effected cars?
The answer is quite simple, but not mentioned.....The heat exchanger !!
The heat exchanger is mounted to the top of the engine case and directly above the #6 cylinder ( the one most likely to score first)...and it transfers the heat of the oil under hard operation to the coolant on bank 2 cylinders.....The extra heat thins/lowers the oil viscosity and oil film protection for the cylinders...
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Keeping the highest quality, robustly viscous oil protection, keeping the cooling system/temperature as low as possible ( in the normal range) and in top shape, will avoid the bore scoring in Lokasil..
Once bore scoring has started, it can't be stopped. The only reasonable repair is to get rid of the Lokasil... As Baz correctly stated, he had trying to replicate the factory process that was invented by KolbenSchmit and the results were disastrous/not long lasting...That process is extremely difficult to recreate, even Porsche had difficulty in the consistency of the process and is why some cars have higher blow-by than others....
If you have bore scoring on Loksail Cylinders, the only solution is to go to something else...Nickasil is the preferred choice at this time ( even though it is an older process )
Also FWIW::: the cylinders can be scoped through the wrist pin access hole for bank 2 ( the one most likely to score) , It is much easier than through the plugs, OR through the Sump.( you don't even have to drain the oil to scope through the wrist pin hole)....but pulling the sump is always a good idea.....you can learn so much about the engine from dropping the sump and having a look..
Skip. Interesting thoughts on the heat exchanger which facilitates a question. If one would replace the 996 heat exchanger with the 20% larger 997S heat exchanger on their 996, would this potentially add more heat and therefore risk for bore scoring on bank 2?
We tear down and inspect 3-5 M9X engines a week and have yet to see one where scoping from the bottom would have revealed more information than scoping from the top. And it's near impossible to get to all of the cylinders from the bottom. If scoring is most prevalent on the thrust face then logic has it that it occurs during the combustion phase of the 4 stroke cycle. Meaning that it would start from the top and work downward. Scoping through the plug holes is always our recommended method.
Brandon, two questions on Baz's paper.
1. What "hard" coated pistons are used by Hartech instead of "soft" coated?
2. Can you offer more details on why a 3rd radiator could make things worse?
@Porschetech3 interesting theory on the heat exchanger. I would love to be able to wrap some data around that. If we can measure it, we can improve it.
We literally see about everything. Lots of spun rod bearings, real bore scoring, false bore scoring, bent valves, about 30% elective rebuilds, and then all of the core engines from one of the largest LS swappers.
@GC996 the hard coating referred to is DLC. I understand Baz’s concepts on center radiators from technical standpoint, but from a practical standpoint, the center radiator will typical (doesn’t do much in stop and go traffic) reduce max oil temps which is why we always recommend them.
Here a pics of cylinder 4, 5, and 6 of an engine we got in yesterday for a race build from a shop so not sure of the background on it. But it has one cylinder that is heavily scored, on that is in the beginning stages of scoring (2 deep grooves), and one that is similar to what we call false scoring which is scuffs with no depth. The redline is drawn where the top of the piston would be.
Heavy scoring, definitely would consume oil and have soot on pipe. Beginning of scoring with two deep grooves. May or may not have symptoms associated with it. Light scuffing. Often, shops will mistake cylinders similar to this for bore scoring.
The conclusion that can be drawn is the best thing any 996 owner can do is run damn good oil with high viscosity and change it often. It solves for alot of problems.
what single thing can a finger be pointed at, that would cause bore scoring to start most likely on Bank 2 on the most effected cars?
The answer is quite simple, but not mentioned.....The heat exchanger !!
The heat exchanger is mounted to the top of the engine case and directly above the #6 cylinder ( the one most likely to score first)...and it transfers the heat of the oil under hard operation to the coolant on bank 2 cylinders.....The extra heat thins/lowers the oil viscosity and oil film protection for the cylinders...
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Interesting.
Well very possible could be 100% correct. Sounds plausible...
Might be time to take a old 996 oil cooler, cut the mounting plate off. Weld some fittings on it to bypass the water, and route new oil lines to engine bay. Or where ever u can find room for a small air to oil cooler with high cfm fan.
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Could rig up numerous ways to control the fan, or let it run all the time.
Might as well also install 2 fittings in return and supply oil lines to measure oil temperature & pressure. Then you could see how much temp the oil cooler drops the oil, without the 200° water to cool oil. Just using ambient temp air might really cool oil down if set up right..?
This remote air to oil cooler system could add 2 more additional benefits, along with above benefits...
1) might add an extra quart of oil.
2) could increase cooling system capacity by deleting the btu load from oil cooler, especially right above #6 cylinder.
The oil cooler is also an oil heater for the colder climates. The coolant temp rises faster than the oil temp - so in cold climates the water will help bring the oil temp up to operating temp faster for better lubrication.
The oil cooler is also an oil heater for the colder climates. The coolant temp rises faster than the oil temp - so in cold climates the water will help bring the oil temp up to operating temp faster for better lubrication.
-Tom
Many ways to control the oil cooler fan. In colder climates could use a temp switch/relay on the cooler to only allow fan to come on at a predetermined oil temp..?
With all we are discussing on water and oil cooling and the things to be aware of, what's the better option for more EFFECTIVE and SAFER cooling.
1. Add the bigger 997s oil cooler on the 996 w/o adding the 3rd radiator.
2. Add the 3rd radiator w/o adding the bigger 997s oil cooler
3. Add both
4. Don't add either
Thoughts?
Add: if the oil cooler is potentially responsible for adding to bore scoring in 6, would adding the bigger 997s cooler add to the problem?
Skip. Interesting thoughts on the heat exchanger which facilitates a question. If one would replace the 996 heat exchanger with the 20% larger 997S heat exchanger on their 996, would this potentially add more heat and therefore risk for bore scoring on bank 2?
Doesn't the 997 also have this issue? I believe the answer is yes.
Might be time to take a old 996 oil cooler, cut the mounting plate off. Weld some fittings on it to bypass the water, and route new oil lines to engine bay. Or where ever u can find room for a small air to oil cooler with high cfm fan.
09-06-2024 | 07:29 AM
