What does a puff of smoke mean?
08-19-2006, 03:26 PM
#16
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Originally Posted by Feehliks
To my humble knowledge, the oil is sprayed to the bottom of the piston, but not on the side of the combustion chamber, but opposite: inside of the piston. Imagine the oil being sprayed along/parallel to the connecting rod.
This is what I meant, the splash valves spray at the *** of the piston, AND on the combustion chamber. When the piston is closed, the majority of the combustion chamber is BEHIND the piston, or the *** of the piston.
08-19-2006, 05:31 PM
#17
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What also could happen is the oil ring (which wipes the walls of the cylinder) can have its gap positioned at the bottom of the barrel...this will allow more oil to seep to the second compression ring. There are three rings in all on the 993 pistons so any oil from the crankcase side to the combustion chamber has to pass all three layers...this is why it does not happen that often. My understanding is that the oil ring is installed with the gap upwards (at least that is what I did on my rebuild) but the rings can and do rotate.
Does anyone know if the Subaru engines have the same characteristic?
Cheers,
Mike
Does anyone know if the Subaru engines have the same characteristic?
Cheers,
Mike
08-20-2006, 12:31 AM
#19
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Hi Mike (nile13),
If your car is a daily-driven car, then you may have oil seeping into one of the combustion chambers. Does the puff of smoke have a slight tinge of blue? ...that and the smell of oil is a dead giveaway for oil burning. If it's really white and/or only occurs on cold mornings, then it's just condensation. Not to alarm you, but if you are getting an oil puff, it is likely valve guide wear as ring wear is pretty rare on stock 911 engines ...whereas guide wear has been one of Porsche's issues since the Carrera. Not that this alone would prompt me to to do head work at the tune of about $5K. How's your overall oil consumption between oil changes?
Mike J.
I've never heard of this happening to Subies (not that it "doesn't" ...just that I've never heard of it nor noticed it myself among owners). My guess is that since aircooled engines have to tolerate a wider heat range, they expand/contract more than a water-cooled one with a much narrower operating temp range. Thus, all 911s (like the venerable VW bugs) will have wider tolerances when the car has cooled, thus increasing the likelihood of oil seeping through. Not that any of this is a "problem," per se. Think of it as a "quirk" inherent to a special car.
Edward
If your car is a daily-driven car, then you may have oil seeping into one of the combustion chambers. Does the puff of smoke have a slight tinge of blue? ...that and the smell of oil is a dead giveaway for oil burning. If it's really white and/or only occurs on cold mornings, then it's just condensation. Not to alarm you, but if you are getting an oil puff, it is likely valve guide wear as ring wear is pretty rare on stock 911 engines ...whereas guide wear has been one of Porsche's issues since the Carrera. Not that this alone would prompt me to to do head work at the tune of about $5K. How's your overall oil consumption between oil changes?
Mike J.
I've never heard of this happening to Subies (not that it "doesn't" ...just that I've never heard of it nor noticed it myself among owners). My guess is that since aircooled engines have to tolerate a wider heat range, they expand/contract more than a water-cooled one with a much narrower operating temp range. Thus, all 911s (like the venerable VW bugs) will have wider tolerances when the car has cooled, thus increasing the likelihood of oil seeping through. Not that any of this is a "problem," per se. Think of it as a "quirk" inherent to a special car.
Edward
08-20-2006, 12:40 AM
#20
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No top end rebuild has been done.
The puff of smoke is white and, I believe, is oil. I have to look see if it only occures after a couple days of car being parked, or if it's actually an everyday occurence. Your question got me thinking, Edward.
There's a bit of an oil smell, although I'd say there's more of a gas smell when the car is first started in the morning.
The puff of smoke is white and, I believe, is oil. I have to look see if it only occures after a couple days of car being parked, or if it's actually an everyday occurence. Your question got me thinking, Edward.
There's a bit of an oil smell, although I'd say there's more of a gas smell when the car is first started in the morning.
