Where does the oil "disappear" to?
06-17-2016, 03:19 PM
#16
Drifting
Oil pools in all types of heads, but especially on horizontally opposed engines, yes. But, the oil that collects in a head is all on the valvetrain side of the head, which is not exposed to the combustion chamber, except through your valve stem seals. I am no technician, but I'll wager that on a healthy, horizontally opposed engine, the bulk of the oil that seeps into the combustion chamber comes from the crank side, from behind the piston.
On the topic of radials, I always wondered why you sometimes see old film of ground crews turning props on a radial prior to start-up. I have never heard of enough oil collecting in a radial cylinder that it could break a connecting rod, but it certainly seems plausible. That oil, too, would come from the crank side, leaking past the piston rings and down into he combustion chamber. I wonder if turning the prop prior to start-up helps to minimize the risk of this occurring?
On the topic of radials, I always wondered why you sometimes see old film of ground crews turning props on a radial prior to start-up. I have never heard of enough oil collecting in a radial cylinder that it could break a connecting rod, but it certainly seems plausible. That oil, too, would come from the crank side, leaking past the piston rings and down into he combustion chamber. I wonder if turning the prop prior to start-up helps to minimize the risk of this occurring?
06-17-2016, 04:06 PM
#17
RL Community Team
Rennlist Member
Rennlist Member
Oil pools in all types of heads, but especially on horizontally opposed engines, yes. But, the oil that collects in a head is all on the valvetrain side of the head, which is not exposed to the combustion chamber, except through your valve stem seals. I am no technician, but I'll wager that on a healthy, horizontally opposed engine, the bulk of the oil that seeps into the combustion chamber comes from the crank side, from behind the piston.
On the topic of radials, I always wondered why you sometimes see old film of ground crews turning props on a radial prior to start-up. I have never heard of enough oil collecting in a radial cylinder that it could break a connecting rod, but it certainly seems plausible. That oil, too, would come from the crank side, leaking past the piston rings and down into he combustion chamber. I wonder if turning the prop prior to start-up helps to minimize the risk of this occurring?
On the topic of radials, I always wondered why you sometimes see old film of ground crews turning props on a radial prior to start-up. I have never heard of enough oil collecting in a radial cylinder that it could break a connecting rod, but it certainly seems plausible. That oil, too, would come from the crank side, leaking past the piston rings and down into he combustion chamber. I wonder if turning the prop prior to start-up helps to minimize the risk of this occurring?
Peace
Bruce in Philly
06-17-2016, 05:00 PM
#18
Three Wheelin'
You turn a radial engine by hand before starting to ensure it's not locked -- not hydraulically locked -- from oil seeping into the cylinders when it sits.
.
.
06-17-2016, 05:44 PM
#19
Race Director
Oil pools in all types of heads, but especially on horizontally opposed engines, yes. But, the oil that collects in a head is all on the valvetrain side of the head, which is not exposed to the combustion chamber, except through your valve stem seals. I am no technician, but I'll wager that on a healthy, horizontally opposed engine, the bulk of the oil that seeps into the combustion chamber comes from the crank side, from behind the piston.
No way any oil that remains in the cylinder/on the piston is going to flow *towards* the hot end of the cylinder.
And once the engine cools the oil's not going to force itself between the piston/rings and cylinder walls.
Barring a bad engine -- which is thankfully quite rare -- the bulk of the oil consumption I believe comes from the AOS failing to remove a sufficient amount of oil vapor from the crankcase fumes.
As a result the engine "burns" oil in the form of vapor. Because most of the time the engine/converters is/are hot we see no smoke. The soot at the exhaust outlets is just the normal byproduct of an otherwise healthy engine (and its converters) which produces around 19lbs of carbon (most in the form of CO2 with the rest as particulate matter) per gallon of gasoline burned.
The only time we might see smoke is upon a cold start. And this comes from oil vapor that has been passed through the AOS to the intake collecting and forming liquid on the intake walls. When the engine is shut off this oil will drain down into a cylinder through open intake valves or puddle on top of intake valves that are closed. When the engine cranks/fires this oil burns but burns inefficiently and smoke is what we see.
The AOS doesn't just let this oil vapor past/by just before the engine is shut off but is a continuous process.
While no one likes an "oil burner" be aware that in almost all cases it is due to a less than efficient/effective AOS (which describes almost all AOS's other than the ones that are just bad and the engines smokes all the time) not a sick engine.
06-17-2016, 06:30 PM
#20
Nordschleife Master
You'd lose.
No way any oil that remains in the cylinder/on the piston is going to flow *towards* the hot end of the cylinder.
And once the engine cools the oil's not going to force itself between the piston/rings and cylinder walls.
Barring a bad engine -- which is thankfully quite rare -- the bulk of the oil consumption I believe comes from the AOS failing to remove a sufficient amount of oil vapor from the crankcase fumes.
As a result the engine "burns" oil in the form of vapor. Because most of the time the engine/converters is/are hot we see no smoke. The soot at the exhaust outlets is just the normal byproduct of an otherwise healthy engine (and its converters) which produces around 19lbs of carbon (most in the form of CO2 with the rest as particulate matter) per gallon of gasoline burned.
The only time we might see smoke is upon a cold start. And this comes from oil vapor that has been passed through the AOS to the intake collecting and forming liquid on the intake walls. When the engine is shut off this oil will drain down into a cylinder through open intake valves or puddle on top of intake valves that are closed. When the engine cranks/fires this oil burns but burns inefficiently and smoke is what we see.
The AOS doesn't just let this oil vapor past/by just before the engine is shut off but is a continuous process.
While no one likes an "oil burner" be aware that in almost all cases it is due to a less than efficient/effective AOS (which describes almost all AOS's other than the ones that are just bad and the engines smokes all the time) not a sick engine.
No way any oil that remains in the cylinder/on the piston is going to flow *towards* the hot end of the cylinder.
And once the engine cools the oil's not going to force itself between the piston/rings and cylinder walls.
Barring a bad engine -- which is thankfully quite rare -- the bulk of the oil consumption I believe comes from the AOS failing to remove a sufficient amount of oil vapor from the crankcase fumes.
As a result the engine "burns" oil in the form of vapor. Because most of the time the engine/converters is/are hot we see no smoke. The soot at the exhaust outlets is just the normal byproduct of an otherwise healthy engine (and its converters) which produces around 19lbs of carbon (most in the form of CO2 with the rest as particulate matter) per gallon of gasoline burned.
The only time we might see smoke is upon a cold start. And this comes from oil vapor that has been passed through the AOS to the intake collecting and forming liquid on the intake walls. When the engine is shut off this oil will drain down into a cylinder through open intake valves or puddle on top of intake valves that are closed. When the engine cranks/fires this oil burns but burns inefficiently and smoke is what we see.
The AOS doesn't just let this oil vapor past/by just before the engine is shut off but is a continuous process.
While no one likes an "oil burner" be aware that in almost all cases it is due to a less than efficient/effective AOS (which describes almost all AOS's other than the ones that are just bad and the engines smokes all the time) not a sick engine.
The AOS is a pollution control thing. Does it really make much difference? What would happen if the AOS circuit was disabled?
06-18-2016, 01:25 PM
#22
Rennlist Member
If just "blocked off", and emissions were not a concern, there still might be a residual issue with pressurizing the crankcase (with blow-by). That might lead to unintended consequences with leaks (if not vented) and tuning. If the crankcase pressure were an issue (undoubtedly, it would be) then an elevation "high point" on the block, and baffling, could be identified to minimize liquid exiting (entrainment and vapors would still occur) the crankcase and a vent installed that would "drip" to the ground or a reservoir...
06-18-2016, 02:02 PM
#23
Race Director
The AOS is intended to -- and it does this just not very effectively -- remove oil vapor from the crankcase fumes. These engines especially with their splash lubed cams/lifter buckets, all those cam chains, and scavenge pumps, generate a lot of oil vapor.
Also, the AOS is to whenever possible keep the crankcase under low pressure to lower the boiling point of gasoline and water to facilitate the removal of these volatile contaminates from the oil.
And last but not least the AOS protects the crankcase from an overpressure condition which could compromise engine seals.
In spite of its less than stellar performance removing it without replacing it with something similar is not advisable.
I can remember a time when engine ventilation consisted of a hose connection to the valve cover with some steel wool in the connector and the hose then ran down along side the engine and its terminating end sticking down below the engine slighly in the air stream serving as a draft tube to when the car was moving forward to create a low pressure area to help pull crankcase fumes from the engine.
At stop lights it was a common site to observe the tubes in some vehicles emitting vapor, water vapor and oil vapor and dripping water and oil. At stop lights in the center of the traffic lanes where countless vehicles dripped this mess from the draft tube was a real, well, mess.
At that time engines typically needed a top end job sometimes at 30K miles miles and a bottom end rebuild at 50K or thereabouts. 100K mile untouched engines were rare.
And engine sludge was a real problem.
Proper crankcase ventilation plays a vital role in modern engine cleanliness and longevity.
06-18-2016, 02:37 PM
#24
Nordschleife Master
The AOS is more than a pollution control device.
The AOS is intended to -- and it does this just not very effectively -- remove oil vapor from the crankcase fumes. These engines especially with their splash lubed cams/lifter buckets, all those cam chains, and scavenge pumps, generate a lot of oil vapor.
Also, the AOS is to whenever possible keep the crankcase under low pressure to lower the boiling point of gasoline and water to facilitate the removal of these volatile contaminates from the oil.
And last but not least the AOS protects the crankcase from an overpressure condition which could compromise engine seals.
In spite of its less than stellar performance removing it without replacing it with something similar is not advisable.
I can remember a time when engine ventilation consisted of a hose connection to the valve cover with some steel wool in the connector and the hose then ran down along side the engine and its terminating end sticking down below the engine slighly in the air stream serving as a draft tube to when the car was moving forward to create a low pressure area to help pull crankcase fumes from the engine.
At stop lights it was a common site to observe the tubes in some vehicles emitting vapor, water vapor and oil vapor and dripping water and oil. At stop lights in the center of the traffic lanes where countless vehicles dripped this mess from the draft tube was a real, well, mess.
At that time engines typically needed a top end job sometimes at 30K miles miles and a bottom end rebuild at 50K or thereabouts. 100K mile untouched engines were rare.
And engine sludge was a real problem.
Proper crankcase ventilation plays a vital role in modern engine cleanliness and longevity.
The AOS is intended to -- and it does this just not very effectively -- remove oil vapor from the crankcase fumes. These engines especially with their splash lubed cams/lifter buckets, all those cam chains, and scavenge pumps, generate a lot of oil vapor.
Also, the AOS is to whenever possible keep the crankcase under low pressure to lower the boiling point of gasoline and water to facilitate the removal of these volatile contaminates from the oil.
And last but not least the AOS protects the crankcase from an overpressure condition which could compromise engine seals.
In spite of its less than stellar performance removing it without replacing it with something similar is not advisable.
I can remember a time when engine ventilation consisted of a hose connection to the valve cover with some steel wool in the connector and the hose then ran down along side the engine and its terminating end sticking down below the engine slighly in the air stream serving as a draft tube to when the car was moving forward to create a low pressure area to help pull crankcase fumes from the engine.
At stop lights it was a common site to observe the tubes in some vehicles emitting vapor, water vapor and oil vapor and dripping water and oil. At stop lights in the center of the traffic lanes where countless vehicles dripped this mess from the draft tube was a real, well, mess.
At that time engines typically needed a top end job sometimes at 30K miles miles and a bottom end rebuild at 50K or thereabouts. 100K mile untouched engines were rare.
And engine sludge was a real problem.
Proper crankcase ventilation plays a vital role in modern engine cleanliness and longevity.
06-18-2016, 02:41 PM
#25
The AOS is more than a pollution control device.
The AOS is intended to -- and it does this just not very effectively -- remove oil vapor from the crankcase fumes. These engines especially with their splash lubed cams/lifter buckets, all those cam chains, and scavenge pumps, generate a lot of oil vapor.
Also, the AOS is to whenever possible keep the crankcase under low pressure to lower the boiling point of gasoline and water to facilitate the removal of these volatile contaminates from the oil.
And last but not least the AOS protects the crankcase from an overpressure condition which could compromise engine seals.
In spite of its less than stellar performance removing it without replacing it with something similar is not advisable.
I can remember a time when engine ventilation consisted of a hose connection to the valve cover with some steel wool in the connector and the hose then ran down along side the engine and its terminating end sticking down below the engine slighly in the air stream serving as a draft tube to when the car was moving forward to create a low pressure area to help pull crankcase fumes from the engine.
At stop lights it was a common site to observe the tubes in some vehicles emitting vapor, water vapor and oil vapor and dripping water and oil. At stop lights in the center of the traffic lanes where countless vehicles dripped this mess from the draft tube was a real, well, mess.
At that time engines typically needed a top end job sometimes at 30K miles miles and a bottom end rebuild at 50K or thereabouts. 100K mile untouched engines were rare.
And engine sludge was a real problem.
Proper crankcase ventilation plays a vital role in modern engine cleanliness and longevity.
The AOS is intended to -- and it does this just not very effectively -- remove oil vapor from the crankcase fumes. These engines especially with their splash lubed cams/lifter buckets, all those cam chains, and scavenge pumps, generate a lot of oil vapor.
Also, the AOS is to whenever possible keep the crankcase under low pressure to lower the boiling point of gasoline and water to facilitate the removal of these volatile contaminates from the oil.
And last but not least the AOS protects the crankcase from an overpressure condition which could compromise engine seals.
In spite of its less than stellar performance removing it without replacing it with something similar is not advisable.
I can remember a time when engine ventilation consisted of a hose connection to the valve cover with some steel wool in the connector and the hose then ran down along side the engine and its terminating end sticking down below the engine slighly in the air stream serving as a draft tube to when the car was moving forward to create a low pressure area to help pull crankcase fumes from the engine.
At stop lights it was a common site to observe the tubes in some vehicles emitting vapor, water vapor and oil vapor and dripping water and oil. At stop lights in the center of the traffic lanes where countless vehicles dripped this mess from the draft tube was a real, well, mess.
At that time engines typically needed a top end job sometimes at 30K miles miles and a bottom end rebuild at 50K or thereabouts. 100K mile untouched engines were rare.
And engine sludge was a real problem.
Proper crankcase ventilation plays a vital role in modern engine cleanliness and longevity.
06-18-2016, 02:55 PM
#26
Racer
Join Date: Mar 2014
Location: Brentwood
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Still not a good idea. There are enough poor maintained cars out there that continue to seep.