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Sparkling oil, time for IMS Replacement ?
- Thread starter Fabs911
- Start date
jond58 said:
I have been searching about that as well and indeed can happen to any 996 of 997.1.
it's another thing to keep in mind e look for and prevent it.
However, it doesn't seem that I have any symptoms of bore scoring but I'll keep my on it. and try the install a Low-Temperature Thermostat and not worry to much.
bazhart
Barcelona
- Joined
- 20 May 2009
- Messages
- 1,343
There was a down and up side to the earlier engines (up to the last 996 3.4's) which cracked or "D" chunked (because the thin open deck cylinders were not strong enough to avoid flexing and stretching oval until they cracked). However they also used hard iron coated pistons so did not suffer bore scoring.
Later engines (late 3.4 996's, 3.6, 3.8 and Cayman S engines) changed the alloy casting mix to include bigger silicon particles making the cylinders stronger (unlikely to crack) - so far so good - but then combined that with softer coated pistons that then can score bores.
All Lokasil and Alusil bores (like all wear modes in any parts) gradually release particles. The size of the particles influences the damage they can do.
Most metallic particles are too small to not simply sit between the metal parts inside the oil film and flow round to be picked up by the oil filter. The silicon particles in Alusil and Lokasil are big enough to potentially cause problems which the harder iron coated pistons minimised. The larger particles in the later engines combined with softer piston coatings resulted in damage over time with some cylinders (and some coatings on some pistons) turning out better than others and introducing a random element to predicting life span.
Nikasil also has silicon particles but they are about on tenth of the size of those in Lokasil or Alusil and better bonded into the substrate with very slow release rates anyway and can survive without any piston coatings as a result.
Support rings in the top of the earlier engines could have removed or eliminated cracking and "D" chunking while fitting the hard iron pistons to the later stiffer cylinders could have avoided scoring.
Out of the frying pan into the fire seems appropriate to describe the outcome.
Baz
Later engines (late 3.4 996's, 3.6, 3.8 and Cayman S engines) changed the alloy casting mix to include bigger silicon particles making the cylinders stronger (unlikely to crack) - so far so good - but then combined that with softer coated pistons that then can score bores.
All Lokasil and Alusil bores (like all wear modes in any parts) gradually release particles. The size of the particles influences the damage they can do.
Most metallic particles are too small to not simply sit between the metal parts inside the oil film and flow round to be picked up by the oil filter. The silicon particles in Alusil and Lokasil are big enough to potentially cause problems which the harder iron coated pistons minimised. The larger particles in the later engines combined with softer piston coatings resulted in damage over time with some cylinders (and some coatings on some pistons) turning out better than others and introducing a random element to predicting life span.
Nikasil also has silicon particles but they are about on tenth of the size of those in Lokasil or Alusil and better bonded into the substrate with very slow release rates anyway and can survive without any piston coatings as a result.
Support rings in the top of the earlier engines could have removed or eliminated cracking and "D" chunking while fitting the hard iron pistons to the later stiffer cylinders could have avoided scoring.
Out of the frying pan into the fire seems appropriate to describe the outcome.
Baz
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