Bore Scoring prevention?
11-09-2021, 06:58 PM
#31
Last night at freeway speeds I couldn't get my oil temp past 150F. Ambient sea level temps were low 50s and the rain was scrubbing heat off of the radiators quickly. Cool water many cool oil.
My knowledge of mechanics and thermodynamics would indicate that once stabilized oil would be hotter than water. There are some here that disagree with that.
But in hot thin mountain air I've seen oil temps that were close to 275F. I'm sure the oil was hotter than the water. So technically last night my thermostat never opened?
The 125F difference between winter conditions and summer is pretty significant in my mind. If the thermostat is operating to control water temperatures, and that thermally controlled water was stripping heat from the oil, you would think the water temp used to cool the oil temp would not vary quite that much.
As a comparison, my wife's car puts out 200HP per liter and in all conditions the temperature of oil and water varies by less than 5F. And that is fluctuation as the thermostat opens and closes. But AMG had the luxury of designing the cooling systems from scratch. Porsche engineers were dictated to a flat six motor producing more and more power within a package that needed to minimize mass. Not an easy task. But they did eventually add an extra radiator to partially "fix" the situation.
Anyway, enough rant. Once your oil temp gauge reaches 175F you're free to produce grins. When I can't get above 150F I simply grin and bear it, avoiding heavy throttle.
The following users liked this post:
Snakebit (11-09-2021)
11-09-2021, 09:39 PM
#32
Originally Posted by Wayne Smith
Porsche got tired of customer concerns regarding water temperature. The water gauge is an idiot light that has little to nothing to do with actual water temp. Oil temp is your concern. And the more you watch this the more you realize that our cars are not thermally stable.
Last night at freeway speeds I couldn't get my oil temp past 150F. Ambient sea level temps were low 50s and the rain was scrubbing heat off of the radiators quickly. Cool water many cool oil.
My knowledge of mechanics and thermodynamics would indicate that once stabilized oil would be hotter than water. There are some here that disagree with that.
But in hot thin mountain air I've seen oil temps that were close to 275F. I'm sure the oil was hotter than the water. So technically last night my thermostat never opened?
The 125F difference between winter conditions and summer is pretty significant in my mind. If the thermostat is operating to control water temperatures, and that thermally controlled water was stripping heat from the oil, you would think the water temp used to cool the oil temp would not vary quite that much.
As a comparison, my wife's car puts out 200HP per liter and in all conditions the temperature of oil and water varies by less than 5F. And that is fluctuation as the thermostat opens and closes. But AMG had the luxury of designing the cooling systems from scratch. Porsche engineers were dictated to a flat six motor producing more and more power within a package that needed to minimize mass. Not an easy task. But they did eventually add an extra radiator to partially "fix" the situation.
Anyway, enough rant. Once your oil temp gauge reaches 175F you're free to produce grins. When I can't get above 150F I simply grin and bear it, avoiding heavy throttle.
Last night at freeway speeds I couldn't get my oil temp past 150F. Ambient sea level temps were low 50s and the rain was scrubbing heat off of the radiators quickly. Cool water many cool oil.
My knowledge of mechanics and thermodynamics would indicate that once stabilized oil would be hotter than water. There are some here that disagree with that.
But in hot thin mountain air I've seen oil temps that were close to 275F. I'm sure the oil was hotter than the water. So technically last night my thermostat never opened?
The 125F difference between winter conditions and summer is pretty significant in my mind. If the thermostat is operating to control water temperatures, and that thermally controlled water was stripping heat from the oil, you would think the water temp used to cool the oil temp would not vary quite that much.
As a comparison, my wife's car puts out 200HP per liter and in all conditions the temperature of oil and water varies by less than 5F. And that is fluctuation as the thermostat opens and closes. But AMG had the luxury of designing the cooling systems from scratch. Porsche engineers were dictated to a flat six motor producing more and more power within a package that needed to minimize mass. Not an easy task. But they did eventually add an extra radiator to partially "fix" the situation.
Anyway, enough rant. Once your oil temp gauge reaches 175F you're free to produce grins. When I can't get above 150F I simply grin and bear it, avoiding heavy throttle.
04-26-2024, 12:56 PM
#33
Rennlist Member
This is a great point, the 997.1 and 997.2 have very different engines with very different bore scoring mechanisms. That's why the failure signature and failure rates are so different, in the 9A1 Porsche reduced the cause of the M96/97 scoring, but inadvertently introduced a new scoring mechanism (the siezing issue). Fortunately it appears to happen at a much lower rate than that seen on the 997.1, at least so far.
Good advice for both engines is to not lug the engine and to keep the revs low until the oil is at operating temperature. These are at potentially at odds with each other so it effectively means babying the car until the engine has reached a uniform temp. The goal is to keep engine stresses low at first so the pistons/cylinders can expand uniformly and reach equilibrium. After that have at it.
Beyond that mitigations (thermostat, oil type, etc.) are probably specific to the engine I would think.
Good advice for both engines is to not lug the engine and to keep the revs low until the oil is at operating temperature. These are at potentially at odds with each other so it effectively means babying the car until the engine has reached a uniform temp. The goal is to keep engine stresses low at first so the pistons/cylinders can expand uniformly and reach equilibrium. After that have at it.
Beyond that mitigations (thermostat, oil type, etc.) are probably specific to the engine I would think.
05-01-2024, 01:52 PM
#34
Intermediate
Cautions...
Watching the video is just another great example of why I would never buy a car that has been tracked.
I remember having arguments in the 996 forum about tracked cars and most guys tracking their car trying to convince me a tracked car gets no more abuse than a non-tracked car.
Just watch some videos of rookie track drivers and easy to understand my logic.
I remember having arguments in the 996 forum about tracked cars and most guys tracking their car trying to convince me a tracked car gets no more abuse than a non-tracked car.
Just watch some videos of rookie track drivers and easy to understand my logic.
YMMV
05-01-2024, 04:15 PM
#35
Rennlist Member
Charles:
You mentioned an improved version of Shell V Power gas in the Bore Scoring Video above. I recently switched from Shell V to Sunoco 94 Ultra which is also a top tier fuel. Based on your comment, should I go back to Shell V power 93 or is Sunoco 94 just as good as the improved Shell V power in terms of everything else and aside from the octane and cost factors? Not sure if I've noticed any difference performance wise, maybe slightly in my head.
2005 C2 3.6 since new, 52k mile, so far runs perfect, burns no oil.
Thanks!
You mentioned an improved version of Shell V Power gas in the Bore Scoring Video above. I recently switched from Shell V to Sunoco 94 Ultra which is also a top tier fuel. Based on your comment, should I go back to Shell V power 93 or is Sunoco 94 just as good as the improved Shell V power in terms of everything else and aside from the octane and cost factors? Not sure if I've noticed any difference performance wise, maybe slightly in my head.
2005 C2 3.6 since new, 52k mile, so far runs perfect, burns no oil.
Thanks!
05-01-2024, 10:40 PM
#36
Rennlist Member
Charles:
You mentioned an improved version of Shell V Power gas in the Bore Scoring Video above. I recently switched from Shell V to Sunoco 94 Ultra which is also a top tier fuel. Based on your comment, should I go back to Shell V power 93 or is Sunoco 94 just as good as the improved Shell V power in terms of everything else and aside from the octane and cost factors? Not sure if I've noticed any difference performance wise, maybe slightly in my head.
2005 C2 3.6 since new, 52k mile, so far runs perfect, burns no oil.
Thanks!
You mentioned an improved version of Shell V Power gas in the Bore Scoring Video above. I recently switched from Shell V to Sunoco 94 Ultra which is also a top tier fuel. Based on your comment, should I go back to Shell V power 93 or is Sunoco 94 just as good as the improved Shell V power in terms of everything else and aside from the octane and cost factors? Not sure if I've noticed any difference performance wise, maybe slightly in my head.
2005 C2 3.6 since new, 52k mile, so far runs perfect, burns no oil.
Thanks!
The following users liked this post:
Sporty (05-02-2024)