Oil's part in cooling engine

[ZeeOSix]

Originally Posted by Virtus_Probi
Originally Posted by ZeeOSix
No arguments here. It's pretty simple, the oil gets heat input from only two things: 1) Shearing of the oil in all parts that shear the oil, and 2) heat transferred into the oil from hotter parts that it comes into contact with. Item 2) is the cooling effect of the oil.

Every engine is different, and the amount of heat the oil picks up from hot parts (ie, oil providing cooling) depends a lot on how well the engine's cooling and oiling system are designed. If the cooling system is lacking efficiency in the head area for instance, oil can certainly pick up heat there and provide some cooling up and beyond what the cooling system provides. No cooling system is 100% efficient to allow oil from not acting as cooling medium to some extent - there will always be some level of added cooling from the oil. For instance around the valve ports (especially the exhaust valves) and spark plug areas where cooling jackets may not be very effective due to the physical location of water jackets to those areas. In hot areas on the heads, the contacting oil is most likely a bit cooler than those surfaces so it also helps cool the heads if the cooling jackets aren't doing a perfect job.

Obviously, the hottest areas that oil comes into contact with is on the piston crown underside, cylinder walls and ring area. The ring area runs pretty hot because they are very close to the combustion gases. Oil in those areas gets the most beating temperature wise. The cylinder walls, even though water cooled, will still have a surface temperature well above any oil splashing on them even if that oil is coming right out of the journal bearings and heated up some from shearing.

Would you say this is still true for a typical turbocharged engine with oil and coolant circulated to the turbo?


Well of course oil circulated through a hot turbo is going to be exposed to high temperature surfaces - most likely higher temps than the bottom of a piston crown. My post wasn't addressing a turboed engine specifically. Oil being ran through a turbo is also providing cooling of the turbo as well as lubrication. And most turboed engines also have some kind of oil cooler to extract all the absorbed heat the oil picks up within the engine and turbo(s).

 

[Shannow]

OK then...

I guess that we now have to add the "cooling" function to the function of piston rings and con-rods then. In performing their primary function, they generate heat and transfer it to another place, so therefore piston rings provide cooling as well....

Given that oil splash (or directed) is a minor player in transferring piston heat to the coolant, then one of it's primary roles is "cooling"

 

[y_p_w]

Originally Posted by ZeeOSix
Well of course oil circulated through a hot turbo is going to be exposed to high temperature surfaces - most likely higher temps than the bottom of a piston crown. My post wasn't addressing a turboed engine specifically. Oil being ran through a turbo is also providing cooling of the turbo as well as lubrication. And most turboed engines also have some kind of oil cooler to extract all the absorbed heat the oil picks up within the engine and turbo(s).

Older turbos were only cooled by the oil, although I suppose then an oil to coolant heat exchanger might also indirectly help to lower the oil temperature and thus the coolant temperature.

However, pretty much all turbos these days are water cooled. In my 2004 there are coolant lines going to the oil cooler (where my filter mounts) and also to the turbo. And that water cooling is nice because on shutdown it cools the turbo through thermal siphon. Still - the oil supposedly still has an important role in drawing heat from the turbo bearings.

 

[ZeeOSix]

Originally Posted by y_p_w
Originally Posted by ZeeOSix
Well of course oil circulated through a hot turbo is going to be exposed to high temperature surfaces - most likely higher temps than the bottom of a piston crown. My post wasn't addressing a turboed engine specifically. Oil being ran through a turbo is also providing cooling of the turbo as well as lubrication. And most turboed engines also have some kind of oil cooler to extract all the absorbed heat the oil picks up within the engine and turbo(s).

Older turbos were only cooled by the oil, although I suppose then an oil to coolant heat exchanger might also indirectly help to lower the oil temperature and thus the coolant temperature.

However, pretty much all turbos these days are water cooled. In my 2004 there are coolant lines going to the oil cooler (where my filter mounts) and also to the turbo. And that water cooling is nice because on shutdown it cools the turbo through thermal siphon. Still - the oil supposedly still has an important role in drawing heat from the turbo bearings.


Dedicated water cooling to the turbo is more efficient cooling, but there is still oil going through the bearings which are much hotter than the oil flowing through them, so the oil is still adding some cooling in addition to the water cooling.

 

[ZeeOSix]

Originally Posted by Shannow
OK then...

I guess that we now have to add the "cooling" function to the function of piston rings and con-rods then. In performing their primary function, they generate heat and transfer it to another place, so therefore piston rings provide cooling as well....

Given that oil splash (or directed) is a minor player in transferring piston heat to the coolant, then one of it's primary roles is "cooling".


That chart doesn't show the effect of any oil cooling ... just the relative level of conductive heat flow and their paths from the hot piston. Obviously rings conduct a lot of heat because they are the direct bridge between the piston and cooler cylinder wall. If any of those parts (including the cylinder wall) are hotter than the oil that comes into contact with them, then the oil is also providing some cooling of those parts (reference steady-state engine temperatures figure I posted earlier).

 

[ZeeOSix]

Ford Coyote 5.0L V8. Apparently not enough oil getting up there under the pistons without these.

 

[Snagglefoot]

I believe the Chev Gen 5 engines also have oil jets.

 

[Shannow]

Originally Posted by ZeeOSix
Originally Posted by Shannow
OK then...

I guess that we now have to add the "cooling" function to the function of piston rings and con-rods then. In performing their primary function, they generate heat and transfer it to another place, so therefore piston rings provide cooling as well....

Given that oil splash (or directed) is a minor player in transferring piston heat to the coolant, then one of it's primary roles is "cooling".


That chart doesn't show the effect of any oil cooling ... just the relative level of conductive heat flow and their paths from the hot piston. Obviously rings conduct a lot of heat because they are the direct bridge between the piston and cooler cylinder wall. If any of those parts (including the cylinder wall) are hotter than the oil that comes into contact with them, then the oil is also providing some cooling of those parts (reference steady-state engine temperatures figure I posted earlier).


Doesn't matter what thecquantum is...the pistin ring is shifting piston heat...therfore as determined in this thread, cooling and heat transfer is one of its core functions.. even though some of its heat is generated by friction.

Same diff e.g. ?

 

[ZeeOSix]

Originally Posted by Shannow
Originally Posted by ZeeOSix
Originally Posted by Shannow
OK then...

I guess that we now have to add the "cooling" function to the function of piston rings and con-rods then. In performing their primary function, they generate heat and transfer it to another place, so therefore piston rings provide cooling as well....

Given that oil splash (or directed) is a minor player in transferring piston heat to the coolant, then one of it's primary roles is "cooling".

That chart doesn't show the effect of any oil cooling ... just the relative level of conductive heat flow and their paths from the hot piston. Obviously rings conduct a lot of heat because they are the direct bridge between the piston and cooler cylinder wall. If any of those parts (including the cylinder wall) are hotter than the oil that comes into contact with them, then the oil is also providing some cooling of those parts (reference steady-state engine temperatures figure I posted earlier).

Doesn't matter what the quantum is...the pistin ring is shifting piston heat...therfore as determined in this thread, cooling and heat transfer is one of its core functions.. even though some of its heat is generated by friction.

Same diff e.g. ?


Not arguing if the piston rings remove heat from the piston crown ... obviously they do to a large degree (as you graphs shows) since they are right in the main hot zone and are a connecting "bridge" to the cooler cylinder wall. Yes, they conduct more heat away then they generate from fiction and oil shearing.

Bottom line is that up under the piston area and on the cylinder walls, the oil that splashes up there or gets squirted up there with oil jets is also contributing to cooling those hot parts. That's one of the hottest areas inside an engine where oil comes into contact (beside in a turbo). It's obviously not nearly as much cooling as what the cooling system provides, but oil still plays a minor role in cooling some hot engine parts. That's all I'm saying, and not trying to quantify the exact level split of oil vs coolant system cooling because every engine is designed a bit differently in those departments.