Thanks molakule.
Sump Oil vs. Coolant Temperatures
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Do you guys think the area of the sump has enough area to make a" big " difference in the oil temp as there are no fins to increase the convection and the larger sump will take longer for the oil to heat up but I'm not sure about the cooler temps.most large diesels have oil coolers.
[ September 16, 2003, 01:20 AM: Message edited by: Steve S ]
[ September 16, 2003, 01:20 AM: Message edited by: Steve S ]
Hi,
I agree with the surface area argument but it does depend on the abount of time the oil is in the sump too.
As a matter of interest, most sumps on heavy trucks are now made of a moulded FRP in order to reduce weight and as an aid to the cooling process. Some have internal air tubes to enable a greater surface area to be exposed
Without going into great detail some past Manufacturer's heavy trucks had insufficient air flow under the cabin ( the tunnel ) to dissipate heat. This caused "whole of life" reliabilty and developement problems over the life of the cabin
Say 10 years or more!
The design of the cooling system - as a total "engine system" - is also vitally important.
In recent times the whole engine system is modelled to cover overall operational application, air flow, coolant capacity, heat dissipation from block/heads
( alloy/steel/magnesium/ceramic and etc )
and likely development of the engine package.
These include coolant pump speed/capacity, oil pump volumn and pressure requirements etc. amongst many others
As an example - some European trucks of 500hp have a 25 litres sump capacity. Some American engined trucks of 500hp have a 40 litres sump capacity.
The design philosophy in each case is different with dual pass radiators, viscos/air drive fans,mandatory synthetic oils and etc. all being part of the equation.
I have been involved in engine development where just a simple increase of 10% in sump capacity has dramatically increased engine reliability by lowering the "core" engine oil temperature
In other applications, increasing the fan size and/or speed has had a similar effect
Australia has been used as a development "test site" by many vehicle manufacturers because of the climate and operational geography of motor vehicles - cars, light & heavy trucks and 4X4s
I hope this adds a bit of interest to the discussion
Regards
I agree with the surface area argument but it does depend on the abount of time the oil is in the sump too.
As a matter of interest, most sumps on heavy trucks are now made of a moulded FRP in order to reduce weight and as an aid to the cooling process. Some have internal air tubes to enable a greater surface area to be exposed
Without going into great detail some past Manufacturer's heavy trucks had insufficient air flow under the cabin ( the tunnel ) to dissipate heat. This caused "whole of life" reliabilty and developement problems over the life of the cabin
Say 10 years or more!
The design of the cooling system - as a total "engine system" - is also vitally important.
In recent times the whole engine system is modelled to cover overall operational application, air flow, coolant capacity, heat dissipation from block/heads
( alloy/steel/magnesium/ceramic and etc )
and likely development of the engine package.
These include coolant pump speed/capacity, oil pump volumn and pressure requirements etc. amongst many others
As an example - some European trucks of 500hp have a 25 litres sump capacity. Some American engined trucks of 500hp have a 40 litres sump capacity.
The design philosophy in each case is different with dual pass radiators, viscos/air drive fans,mandatory synthetic oils and etc. all being part of the equation.
I have been involved in engine development where just a simple increase of 10% in sump capacity has dramatically increased engine reliability by lowering the "core" engine oil temperature
In other applications, increasing the fan size and/or speed has had a similar effect
Australia has been used as a development "test site" by many vehicle manufacturers because of the climate and operational geography of motor vehicles - cars, light & heavy trucks and 4X4s
I hope this adds a bit of interest to the discussion
Regards
MolaKule
Staff member
Doug,
Everyone adds something to the discussion.
"I agree with the surface area argument but it does depend on the amount of time the oil is in the sump too. As a matter of interest, most sumps on heavy trucks are now made of a moulded FRP in order to reduce weight and as an aid to the cooling process. Some have internal air tubes to enable a greater surface area to be exposed."
The longer the "dwell" time in the sump the more cooling there will be, but oil is always flowing from the hot parts of the engine to the sump and back, so oil dwell time can't be too long. If you can't increase oil dwell time, then larger heat exchangers need to be designed into the system to dissipate heat at a faster rate. Those internal air tubes acts as heat exchangers to dissipate heat, so the effective cooling area is increased.
Anytime the thermal stability of the oil can be increased, either by additives and/or extra cooling, the engine reliability will go up.
I still think the Toyota engines prone to sludge (Main Auto Engine Oil Thread) were the result of oil overheating leading to intense thermal oxidation, thus reducing engine reliability. Additionally, the oil drain intervals were probably too long for the high oil temps encountered.
[ September 17, 2003, 03:20 PM: Message edited by: MolaKule ]
Everyone adds something to the discussion.
"I agree with the surface area argument but it does depend on the amount of time the oil is in the sump too. As a matter of interest, most sumps on heavy trucks are now made of a moulded FRP in order to reduce weight and as an aid to the cooling process. Some have internal air tubes to enable a greater surface area to be exposed."
The longer the "dwell" time in the sump the more cooling there will be, but oil is always flowing from the hot parts of the engine to the sump and back, so oil dwell time can't be too long. If you can't increase oil dwell time, then larger heat exchangers need to be designed into the system to dissipate heat at a faster rate. Those internal air tubes acts as heat exchangers to dissipate heat, so the effective cooling area is increased.
Anytime the thermal stability of the oil can be increased, either by additives and/or extra cooling, the engine reliability will go up.
I still think the Toyota engines prone to sludge (Main Auto Engine Oil Thread) were the result of oil overheating leading to intense thermal oxidation, thus reducing engine reliability. Additionally, the oil drain intervals were probably too long for the high oil temps encountered.
[ September 17, 2003, 03:20 PM: Message edited by: MolaKule ]
Theoretically larger sump volume should have little to do with oil temperature overall other things being equal. It will just take longer for it to reach its ultimate temperature. This takes a pretty good amount of time as it is in my observation, it is on the order of minutes of hard pulling before the oil temperature has made or stabilized at a large change. Larger pan area obviously has a lot to do with it though.
Now as far as dwell time, well, this will open a whole can of worms but I don't believe it. Hot fluid does not need to stop and think about it before transferring its energy. The heat transfer formula does not take into account the velocity of any fluid involved, it is just the temperature difference between the two. So it does not matter whether the oil is on its way to the pump or just sitting in an isolated corner of the pan, if the temperature difference is the same the rate of transfer will be the same (instantaneously that is, until the oil becomes cooler and the air becomes warmer, then more flow becomes better).
Birken
Now as far as dwell time, well, this will open a whole can of worms but I don't believe it. Hot fluid does not need to stop and think about it before transferring its energy. The heat transfer formula does not take into account the velocity of any fluid involved, it is just the temperature difference between the two. So it does not matter whether the oil is on its way to the pump or just sitting in an isolated corner of the pan, if the temperature difference is the same the rate of transfer will be the same (instantaneously that is, until the oil becomes cooler and the air becomes warmer, then more flow becomes better).
Birken
Oil flow rate is my friend ! The more turbulent the better !
In response to Patman and others assertions that a thicker more viscous oil is needed to overcome the heating in critical areas, remember, if I have a fluid that maintains its viscosity regardless of localized pressure/heating then I DO NOT want to overkill with a "thicker' fluid causing increased heating due to the viscous friction increase effect.
A poorly informed engine builder or racer will attempt to overcome mechanical friction and induce a localized heating issue by using the wrong ( many times too thick) lube.
Thus my fondness of roughly 11-12 cSt synthetic fluids for auto racing engines as a starting point.
Thanks Mola !
In response to Patman and others assertions that a thicker more viscous oil is needed to overcome the heating in critical areas, remember, if I have a fluid that maintains its viscosity regardless of localized pressure/heating then I DO NOT want to overkill with a "thicker' fluid causing increased heating due to the viscous friction increase effect.
A poorly informed engine builder or racer will attempt to overcome mechanical friction and induce a localized heating issue by using the wrong ( many times too thick) lube.
Thus my fondness of roughly 11-12 cSt synthetic fluids for auto racing engines as a starting point.
Thanks Mola !
Patman
Staff member
I don't believe in super thick oils though, such as the thicker 40wts and 50wts out there, but like you Terry, I believe the thicker 30wts will do very well for most engines, and there are a few other engines such as my LT1 which might even benefit from something closer to 13 or 14 cst, simply because of the larger clearances and the fact that they run hotter oil temps too.
I don't believe there are very many engine designs out there at all which would show very good results with a 15w50 or 20w50 oil though. But yet a lot of our members here, especially those outside of North America, still hang onto that belief.
I don't believe there are very many engine designs out there at all which would show very good results with a 15w50 or 20w50 oil though. But yet a lot of our members here, especially those outside of North America, still hang onto that belief.
How can you create turbulent flow? I know thinner viscosity will become turbulent more easily. Short of redesigning the engine, what else could you change? And how would you know that the particular lube you have chosen is more turbulent than another. I suppose lower oil temps would be a clue.
Jason, By the predominant molecular structure of the lube/liquid. Internal modifications to the oil system. But mostly the lube itself.
The Dyson theory of laminar vs turbulent lubricant flow.
Many disagree with me and I cannot do the math to quantify it but I have successfuly employed the theory for some time !
The Dyson theory of laminar vs turbulent lubricant flow.
Many disagree with me and I cannot do the math to quantify it but I have successfuly employed the theory for some time !
That's what I thought but it seemed like you would basically be shooting blind trying to find one, but apparently not... Pretty cool
Hi,
dwell time is an important issue. The rate of temperature "transfer" in this location will be a factor of the volumn of oil in circulation, the "static" volumn of oil in the sump and the surface area of the sump and its ancillaries.
A major factor is also the amount of exposure of the sumps surface area to air flow. Many oil pans are now ducted for this purpose
Regards
dwell time is an important issue. The rate of temperature "transfer" in this location will be a factor of the volumn of oil in circulation, the "static" volumn of oil in the sump and the surface area of the sump and its ancillaries.
A major factor is also the amount of exposure of the sumps surface area to air flow. Many oil pans are now ducted for this purpose
Regards
Would a larger oil filter also help lower temps?
Hi,
"350" - yes, filters can reduce oil temps. It was/is common to fit large "LuberFiner" type by pass filters to heavy 'dozers and trucks. These were placed in the full airflow, on trucks at least, and held an additional 20 odd liters of oil.
On 'dozers etc. they were fitted in an area of "open air" in order to dissipate heat
I cannot remember before and after "core" sump temperatures but there were significant variances
On a car, fitting a remote oil filter helps too as heat is shed via the hoses and the filter body - and the extra volumn of oil required. Small "parasitic" heat shedding perhaps, but measurable
These "tricks" were often carried out on air cooled "warmed" VWs and Porsches'
Regards
"350" - yes, filters can reduce oil temps. It was/is common to fit large "LuberFiner" type by pass filters to heavy 'dozers and trucks. These were placed in the full airflow, on trucks at least, and held an additional 20 odd liters of oil.
On 'dozers etc. they were fitted in an area of "open air" in order to dissipate heat
I cannot remember before and after "core" sump temperatures but there were significant variances
On a car, fitting a remote oil filter helps too as heat is shed via the hoses and the filter body - and the extra volumn of oil required. Small "parasitic" heat shedding perhaps, but measurable
These "tricks" were often carried out on air cooled "warmed" VWs and Porsches'
Regards
My theory on this is it is a waste of money to use any filter other than designed for the engine. Using a larger oil filter will increase the oil capacity, but the oil will still heat to the same temp, just take it longer to do it. Also once it is hot, the increased capacity takes longer to cool down.
Put a mechanical gage on a trans. or engine oil pan. Take the readings, now increase the size of the sump/pan/filter and the readings will be the same, but may have to drive 2 miles more to get it to that temp.
The solution is to add an oil/trans fluid cooler prior to any other component on the front of the vehicle, just behind the grille.
JMO
MolaKule
Staff member
"Now as far as dwell time, well, this will open a whole can of worms but I don't believe it."
It's a fact. More volume generally equals more surface area = greater heat dissipation.
The longer the oil is allowed to sit before being pumped back up to the hot engine, the cooler it will become over time.
Now in a real sump, the oil is mixed so you have short dwell time, which means that you want to design enough surface area into the heat exchangers to keep oil temps from peaking into the oil oxidation ranges, because the dwell time in the real world isn't long enough to properly cool the oil.
Oil pans, lower engine blocks, Water jackets, and oil coolers all contribute to heat transfer from the oil to the air.
[ September 18, 2003, 12:17 PM: Message edited by: MolaKule ]
It's a fact. More volume generally equals more surface area = greater heat dissipation.
The longer the oil is allowed to sit before being pumped back up to the hot engine, the cooler it will become over time.
Now in a real sump, the oil is mixed so you have short dwell time, which means that you want to design enough surface area into the heat exchangers to keep oil temps from peaking into the oil oxidation ranges, because the dwell time in the real world isn't long enough to properly cool the oil.
Oil pans, lower engine blocks, Water jackets, and oil coolers all contribute to heat transfer from the oil to the air.
[ September 18, 2003, 12:17 PM: Message edited by: MolaKule ]
MolaKule
Staff member
"The heat transfer formula does not take into account the velocity of any fluid involved, it is just the temperature difference between the two."
There are more complex heat conduction and heat convection transfer formulas that are called, "time dependant equations" which show that flow does effect heat transfer and does affect temperature rise or cooling.
If you didn't have a flow of oil around and through the bearings in an engine, they would self destruct in X amount of time. Oil flow removes heat by "forced" convection.
[ September 18, 2003, 12:27 PM: Message edited by: MolaKule ]
There are more complex heat conduction and heat convection transfer formulas that are called, "time dependant equations" which show that flow does effect heat transfer and does affect temperature rise or cooling.
If you didn't have a flow of oil around and through the bearings in an engine, they would self destruct in X amount of time. Oil flow removes heat by "forced" convection.
[ September 18, 2003, 12:27 PM: Message edited by: MolaKule ]
How can you create turbulent flow? I know thinner viscosity will become turbulent more easily. Short of redesigning the engine, what else could you change? And how would you know that the particular lube you have chosen is more turbulent than another. I suppose lower oil temps would be a clue.
I believe Terry likes to have the most sheer stable 20w or 30w to acheive turb but still protect engine. Send a UOA into Terry and he'll unload some info on ya.....
Jason,
I believe Terry likes to have the most sheer stable 20w or 30w to acheive turb but still protect engine. Send a UOA into Terry and he'll unload some info on ya.....
Using standard engineering units, flow changes from laminar to turbulent above a Reynolds number of 2100, or maybe by 3000. R the Reynolds number equals pipe diameter X velocity X density divided by the viscosity. The 2 easiest things to change would be the velocity and viscosity. You could add a higher volume pump, and use thinner oil.
Often it is a challenge coming up with all the data you need to do pipe flow calculations. An average diameter for the oil passages in your engine would be a good one.
Where does the oil absorb the heat from the engine? In the passageways where it might be turbulent, or other, slower moving places? I wonder if that is what the big puddle of oil on top of the head on my truck is for? It is designed so the oil stands about a half inch deep before flowing down to the pan.
A lot of heat is picked up, actually generated by shear, in the journal bearings.
My educated guess is that oil running over surfaces (like the puddle on top of your truck head) in the engine is either 1st or second in amount of heat picked up. The surface area of oil passages inside an engine is so small compared to the areas wet by the oil as it runs over head surfaces, etc, that it is had to see how heat picked up in the passages could be a major factor.
Adding a higher flow pump would likely add more head from pumping losses than anything else.
"Characteristic distance" is the more general and useful dimension used in Reynolds number calculations than pipe diameter.
Here is a useful Reynolds number calculator.
http://www.efunda.com/formulae/fluids/calc_reynolds.cfm#calc
Another way to get turbulant flow is to make the surface irregular in a shape that encourages turbulant flow.
Oil coming out of the journal bearings and getting flung off the crankshaft is definitely momentarily turbulant when it next contacts the engine.
This may be apples to watermelons, but in a car that has been outside at -30 for several hours, can anyone think of what spot of the engine would be best to 'zap' with a torch of some sort to help the engine heat up?
Just tryin' to reduce wear numbers in a Manitoba winter
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